ORCID Profile
0000-0001-6733-0993
Current Organisation
University of Technology Sydney
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Research Topics
In Research Link Australia (RLA), "Research Topics" refer to ANZSRC FOR and SEO codes. These topics are either sourced from ANZSRC FOR and SEO codes listed in researchers' related grants or generated by a large language model (LLM) based on their publications.
Top 5 Research Topics
ANZSRC Field of Research (FoR)
Physical Geography and Environmental Geoscience | Palaeoclimatology | Climatology (Incl. Palaeoclimatology) | Climate Change Processes | Atmospheric Sciences | Geochronology | Quaternary Environments | Geology | Geochemistry | Archaeological Science | Conservation And Biodiversity | Hydrogeology | Environmental Science and Management | Glaciology | Archaeological Science | Isotope Geochemistry | Ecological Impacts of Climate Change | Archaeology | Optical Properties of Materials | History: Australian | Resources Engineering and Extractive Metallurgy not elsewhere classified | Aboriginal and Torres Strait Islander Archaeology | Evolutionary Biology not elsewhere classified | Geochronology | Groundwater Hydrology | Palaeoecology | Composite and Hybrid Materials | Photonics, Optoelectronics and Optical Communications | Galactic Astronomy | Soil Sciences | Global Change Biology | Structural Engineering | Archaeology Of Hunter-Gatherer Societies (Incl. Pleistocene | Land Capability And Soil Degradation | Global Change Biology | Enzymes | Theoretical and Computational Chemistry not elsewhere classified | Computational Fluid Dynamics | Carbon Sequestration Science | Bioinformatics | Particle Physics | Tectonics
ANZSRC Socio-Economic Objective (SEO)
Climate change | Effects of Climate Change and Variability on Australia (excl. Social Impacts) | Expanding Knowledge in the Earth Sciences | Biological sciences | Earth sciences | Climate variability | Flora, Fauna and Biodiversity at Regional or Larger Scales | Effects of Climate Change and Variability on Antarctic and Sub-Antarctic Environments (excl. Social Impacts) | Ecosystem Adaptation to Climate Change | Effects of Climate Change and Variability on New Zealand (excl. Social Impacts) | Climate Variability (excl. Social Impacts) | Understanding Australia's Past | Effects of Climate Change and Variability on the South Pacific (excl. Australia and New Zealand) (excl. Social Impacts) | Living resources (flora and fauna) | Integrated (ecosystem) assessment and management | Civil Construction Design | Antarctic and Sub-Antarctic Oceanography | Land and water management | Environmental and resource evaluation not elsewhere classified | Oil and Gas Extraction | Oceanic processes (excl. climate related) | Physical and Chemical Conditions of Water in Fresh, Ground and Surface Water Environments (excl. Urban and Industrial Use) | Cardiovascular System and Diseases | Ecosystem Assessment and Management of Fresh, Ground and Surface Water Environments | Aerospace Transport not elsewhere classified | Expanding Knowledge in Technology | Sparseland, Permanent Grassland and Arid Zone Land and Water Management | Global Effects of Climate Change and Variability (excl. Australia, New Zealand, Antarctica and the South Pacific) (excl. Social Impacts) | Expanding Knowledge in the Chemical Sciences | Expanding Knowledge in the Physical Sciences | Expanding Knowledge in Engineering | Expanding Knowledge in the Agricultural and Veterinary Sciences | Expanding Knowledge in the Biological Sciences | Farmland, Arable Cropland and Permanent Cropland Land Management |
Related Links
Publications
Redating the advance of the New Zealand Franz Josef Glacier during the Last Termination: evidence for asynchronous climate change
Publisher: Elsevier BV
Date: 12-2007
SHCal20 Southern Hemisphere Calibration, 0–55,000 Years cal BP
Publisher: Cambridge University Press (CUP)
Date: 08-2020
DOI: 10.1017/RDC.2020.59
Abstract: Early researchers of radiocarbon levels in Southern Hemisphere tree rings identified a variable North-South hemispheric offset, necessitating construction of a separate radiocarbon calibration curve for the South. We present here SHCal20, a revised calibration curve from 0–55,000 cal BP, based upon SHCal13 and fortified by the addition of 14 new tree-ring data sets in the 2140–0, 3520–3453, 3608–3590 and 13,140–11,375 cal BP time intervals. We detail the statistical approaches used for curve construction and present recommendations for the use of the Northern Hemisphere curve (IntCal20), the Southern Hemisphere curve (SHCal20) and suggest where application of an equal mixture of the curves might be more appropriate. Using our Bayesian spline with errors-in-variables methodology, and based upon a comparison of Southern Hemisphere tree-ring data compared with contemporaneous Northern Hemisphere data, we estimate the mean Southern Hemisphere offset to be 36 ± 27 14 C yrs older.
Palaeogenomics of the Hydrocarbon Producing Microalga Botryococcus braunii
Publisher: Springer Science and Business Media LLC
Date: 11-02-2019
DOI: 10.1038/S41598-018-38236-5
Abstract: Botryococcus braunii is a colonial microalga that appears early in the fossil record and is a sensitive proxy of environmental and hydroclimatic conditions. Palaeozoic Botryococcus fossils which contribute up to 90% of oil shales and approximately 1% of crude oil, co-localise with diagnostic geolipids from the degradation of source-signature hydrocarbons. However more recent Holocene sediments demonstrate no such association. Consequently, Botryococcus are identified in younger sediments by morphology alone, where potential misclassifications could lead to inaccurate paleoenvironmental reconstructions. Here we show that a combination of flow cytometry and ancient DNA (aDNA) sequencing can unambiguously identify Botryococcus microfossils in Holocene sediments with hitherto unparalleled accuracy and rapidity. The application of aDNA sequencing to microfossils offers a far-reaching opportunity for understanding environmental change in the recent geological record. When allied with other high-resolution palaeoenvironmental information such as aDNA sequencing of humans and megafauna, aDNA from microfossils may allow a deeper and more precise understanding of past environments, ecologies and migrations.
Pairwise surface drifter separation in the western Pacific sector of the Southern Ocean
Publisher: American Geophysical Union (AGU)
Date: 10-2015
DOI: 10.1002/2015JC010972
RADIOCARBON PROTOCOLS AND FIRST INTERCOMPARISON RESULTS FROM THE CHRONOS 14CARBON-CYCLE FACILITY, UNIVERSITY OF NEW SOUTH WALES, SYDNEY, AUSTRALIA
Publisher: Cambridge University Press (CUP)
Date: 11-05-2021
DOI: 10.1017/RDC.2021.23
Abstract: The Chronos 14 Carbon-Cycle Facility is a new radiocarbon laboratory at the University of New South Wales, Australia. Built around an Ionplus 200 kV MIni-CArbon DAting System (MICADAS) Accelerator Mass Spectrometer (AMS) installed in October 2019, the facility was established to address major challenges in the Earth, Environmental and Archaeological sciences. Here we report an overview of the Chronos facility, the pretreatment methods currently employed (bones, carbonates, peat, pollen, charcoal, and wood) and results of radiocarbon and stable isotope measurements undertaken on a wide range of s le types. Measurements on international standards, known-age and blank s les demonstrate the facility is capable of measuring 14 C s les from the Anthropocene back to nearly 50,000 years ago. Future work will focus on improving our understanding of the Earth system and managing resources in a future warmer world.
The 5.2 ka climate event: Evidence from stable isotope and multi-proxy palaeoecological peatland records in Ireland
Publisher: Elsevier BV
Date: 09-2015
Is there any evidence for regional atmospheric 14C offsets in the Southern Hemisphere?
Publisher: Cambridge University Press (CUP)
Date: 2013
DOI: 10.2458/AZU_JS_RC.V55I2.16104
Abstract: Center for Accelerator Mass Spectrometry (CAMS) Tasmanian Huon pine ( Lagarostrobos franklinii ) decadal measurements for the interval AD 745–855 suggest a mean interhemispheric radiocarbon offset (20 ± 5 yr), which is considerably lower than the previously reported mean interhemispheric offset for the last 2 millennia (44 ± 17 yr). However, comparable University of Waikato (Wk) New Zealand kauri ( Agathis australis ) measurements show significantly higher values (56 ± 6 yr), suggesting the possibility of a temporary geographic (intrahemispheric) offset between Tasmania, Australia, and Northland, New Zealand, during at least 1 common time interval. Here, we report 9 new Wk Tasmanian Huon pine measurements from the decades showing the largest Huon/kauri difference. We show statistically indistinguishable Wk Huon and Wk kauri 14 C ages, thus dispelling the suggestion of a 14 C geographic offset between Tasmania and Northland.
Synergistic roles of climate warming and human occupation in Patagonian megafaunal extinctions during the Last Deglaciation
Publisher: American Association for the Advancement of Science (AAAS)
Date: 03-06-2016
Abstract: Patagonian megafaunal extinctions reveal synergistic roles of climate change and human impacts.
Brief communication: Changing mid-twentieth century Antarctic sea ice variability linked to tropical forcing
Publisher: Copernicus GmbH
Date: 25-04-2017
DOI: 10.5194/TC-2017-51
Abstract: Abstract. Satellite observations demonstrate Antarctic sea ice extent increased between late-1978 and 2015, with significant spatial and seasonal variability. Late spring retreat off George V Land is a major component of the observed increase, but the paucity of proxy records makes interpretation of trends (and impacts) challenging. Here Earth-system modelling and reanalysis demonstrate tropical Pacific warming can trigger an atmospheric Rossby wave response during the austral spring, delaying sea-ice retreat off George V Land. Our results provide new insights into the spatial and temporal role low latitudes play in Antarctic sea-ice production, drift and ocean circulation on decadal to centennial timescales.
Examining past and projecting future: an 800-year streamflow reconstruction of the Australian Murray river
Publisher: IOP Publishing
Date: 25-09-2023
Introduction: Integrating high-resolution past climate records for future prediction in the Australasian region
Publisher: Wiley
Date: 2006
DOI: 10.1002/JQS.1072
Testing solar forcing of pervasive Holocene climate cycles
Publisher: Wiley
Date: 2005
DOI: 10.1002/JQS.927
Integration of ice-core, marine and terrestrial records for the Australian last glacial maximum and termination: A contribution from the OZ INTIMATE group
Publisher: Wiley
Date: 2006
DOI: 10.1002/JQS.1073
Extension of New Zealand kauri (agathis australis) tree-ring chronologies into Oxygen Isotope Stage (OIS) 3
Publisher: Wiley
Date: 2006
DOI: 10.1002/JQS.1075
Evidence for suppressed mid-Holocene northeastern Australian monsoon variability from coral luminescence
Publisher: American Geophysical Union (AGU)
Date: 06-2014
DOI: 10.1002/2014PA002630
Radiocarbon dating of charcoal from tropical sequences: Results from the Niah Great Cave, Sarawak, and their broader implications
Publisher: Wiley
Date: 02-2009
DOI: 10.1002/JQS.1197
A comprehensive database of quality-rated fossil ages for Sahul’s Quaternary vertebrates
Publisher: Springer Science and Business Media LLC
Date: 19-07-2016
Abstract: The study of palaeo-chronologies using fossil data provides evidence for past ecological and evolutionary processes, and is therefore useful for predicting patterns and impacts of future environmental change. However, the robustness of inferences made from fossil ages relies heavily on both the quantity and quality of available data. We compiled Quaternary non-human vertebrate fossil ages from Sahul published up to 2013. This, the FosSahul database, includes 9,302 fossil records from 363 deposits, for a total of 478 species within 215 genera, of which 27 are from extinct and extant megafaunal species (2,559 records). We also provide a rating of reliability of in idual absolute age based on the dating protocols and association between the dated materials and the fossil remains. Our proposed rating system identified 2,422 records with high-quality ages (i.e., a reduction of 74%). There are many applications of the database, including disentangling the confounding influences of hypothetical extinction drivers, better spatial distribution estimates of species relative to palaeo-climates, and potentially identifying new areas for fossil discovery.
A new flow cytometry method enabling rapid purification of fossil pollen from terrestrial sediments for AMS radiocarbon dating
Publisher: Wiley
Date: 03-2013
DOI: 10.1002/JQS.2606
Western Pacific paleoceanography and Paleoclimatology: Land-Sea linkage and variability of centennial to orbital scales
Publisher: Wiley
Date: 12-2012
DOI: 10.1002/JQS.2607
Holocene environmental change at Lake Shudu, Yunnan Province, southwestern China
Publisher: Springer Science and Business Media LLC
Date: 13-05-2012
The New Zealand Kauri (Agathis Australis) Research Project: A Radiocarbon Dating Intercomparison of Younger Dryas Wood and Implications for IntCal13
Publisher: Cambridge University Press (CUP)
Date: 2013
DOI: 10.2458/AZU_JS_RC.V55I2.16217
Abstract: Wc describe here the New Zealand kauri ( Agathis australis ) Younger Dryas (YD) research project, which aims to undertake Δ 14 C analysis of ∼140 decadal floating wood s les spanning the time interval ∼13.1–11.7 kyr cal BP. We report 14 C intercomparison measurements being undertaken by the carbon dating laboratories at University of Waikato (Wk), University of California at Irvine (UCI), and University of Oxford (OxA). The Wk, UCI, and OxA laboratories show very good agreement with an interlaboratory comparison of 12 successive decadal kauri s les (average offsets from consensus values of –7 to +4 14 C yr). A University of Waikato/University of Heidelberg (HD) intercomparison involving measurement of the YD-age Swiss larch tree Ollon505, shows a HD/Wk offset of ∼10–20 14 C yr (HD younger), and strong evidence that the positioning of the Ollon505 series is incorrect, with a recommendation that the 14 C analyses be removed from the IntCal calibration database.
The aftermath of megafaunal extinction: Ecosystem transformation in Pleistocene Australia
Publisher: American Association for the Advancement of Science (AAAS)
Date: 23-03-2012
Abstract: Following the arrival of humans in Australia 40- to 50,000 years ago, many species of large vertebrates rapidly became extinct. By analyzing sediment cores from a site in northeastern Australia, Rule et al. (p. 1483 see the Perspective by McGlone ) show that the extinction of the Australian megafauna caused important ecosystem shifts. Prominent among these were a shift from rainforest vegetation to sclerophyllous vegetation and a sustained increase in the incidence of fire. The cores also provide evidence of the cause of megafaunal extinction in Australia, ruling out climate and anthropogenic fire as possible causes while confirming that the extinctions closely followed human arrival. These findings show how landscapes sometimes have been fundamentally changed by the indirect effects of early humans—which underscores the impact that even prehistoric human societies had on natural systems.
Learning from climates past
Publisher: Springer Science and Business Media LLC
Date: 05-2008
DOI: 10.1038/453158A
Drought variability in the eastern Australia and New Zealand summer drought atlas (ANZDA, CE 1500-2012) modulated by the Interdecadal Pacific Oscillation
Publisher: IOP Publishing
Date: 24-11-2015
Evidence for extreme floods in arid subtropical northwest Australia during the Little Ice Age chronozone (CE 1400–1850)
Publisher: Elsevier BV
Date: 07-2016
Impacts of marine instability across the East Antarctic Ice Sheet on Southern Ocean dynamics
Publisher: Copernicus GmbH
Date: 26-05-2016
DOI: 10.5194/TC-2016-111
Abstract: Abstract. Recent observations and modelling studies have demonstrated the potential for rapid and substantial retreat of large sectors of the East Antarctic Ice Sheet (EAIS). This has major implications for ocean circulation and global sea level. Here we examine the effects of increasing meltwater from the Wilkes Basin, one of the major marine-based sectors of the EAIS, on Southern Ocean dynamics. Climate model simulations reveal that the meltwater flux rapidly stratifies surface waters, leading to a dramatic decrease in the rate of Antarctic Bottom Water formation. The surface ocean cools but, critically, the Southern Ocean warms by more than 1 ºC at depth. This warming is accompanied by a Southern Ocean-wide "domino effect", whereby the warming signal propagates westward with depth. Our results suggest that melting of one sector of the EAIS could result in accelerated warming across other sectors, including the Weddell Sea sector of the West Antarctic Ice Sheet. Thus localised melting of the EAIS could potentially destabilise the wider Antarctic Ice Sheet.
Criteria for assessing the quality of Middle Pleistocene to Holocene vertebrate fossil ages
Publisher: Elsevier BV
Date: 10-2015
Early Last Interglacial ocean warming drove substantial ice mass loss from Antarctica
Publisher: California Digital Library (CDL)
Date: 07-12-2018
Response to Comment on “A global environmental crisis 42,000 years ago”
Publisher: American Association for the Advancement of Science (AAAS)
Date: 19-11-2021
Abstract: Our paper about the impacts of the Lasch s Geomagnetic Excursion 42,000 years ago has provoked considerable scientific and public interest, particularly in the so-called Adams Event associated with the initial transition of the magnetic poles. Although we welcome the opportunity to discuss our new ideas, Hawks’ assertions of misrepresentation are especially disappointing given his limited examination of the material.
Evidence for increased expression of the Amundsen Sea Low over the South Atlantic during the late Holocene
Publisher: Copernicus GmbH
Date: 13-11-2018
Abstract: Abstract. The Amundsen Sea Low (ASL) plays a major role in the climate and environment of Antarctica and the Southern Ocean, including surface air temperature and sea ice concentration changes. Unfortunately, a relative dearth of observational data across the Amundsen and Bellingshausen seas prior to the satellite era (post-1979) limits our understanding of the past behaviour and impact of the ASL. The limited proxy evidence for changes in the ASL are primarily restricted to the Antarctic where ice core evidence suggests a deepening of the atmospheric pressure system during the late Holocene. However, no data have previously been reported from the northern side of the ASL. Here we report a high-resolution, multi-proxy study of a 5000-year-long peat record from the Falkland Islands, a location sensitive to contemporary ASL dynamics which modulates northerly and westerly airflow across the southwestern South Atlantic sector of the Southern Ocean. In combination with climate reanalysis, we find a marked period of wetter, colder conditions most likely the result of enhanced southerly airflow between 5000 and 2500 years ago, suggesting limited ASL influence over the region. After 2500 years ago, drier and warmer conditions were established, implying more westerly airflow and the increased projection of the ASL onto the South Atlantic. The possible role of the equatorial Pacific via atmospheric teleconnections in driving this change is discussed. Our results are in agreement with Antarctic ice core records and fjord sediments from the southern South American coast, and suggest that the Falkland Islands provide a valuable location for reconstructing high southern latitude atmospheric circulation changes on multi-decadal to millennial timescales.
Distal volcanic ash layers in the Lateglacial Interstadial (GI-1): problems of stratigraphic discrimination
Publisher: Elsevier BV
Date: 2008
INTERNATIONAL JOURNAL OF SCIENTIFIC RESEARCH
Publisher: World Wide Journals
Date: 2020
DOI: 10.36106/IJSR
Retreat of the Antarctic Ice Sheet during the Last Interglaciation and implications for future change
Publisher: Wiley
Date: 05-11-2020
Retreat of the Antarctic Ice Sheet during the Last Interglaciation and implications for future change
Publisher: Wiley
Date: 04-08-2021
Introduction to the Special Issue on Climate of the Past 2000 Years: Global and Regional Syntheses
Publisher: Copernicus GmbH
Date: 17-10-2018
DOI: 10.5194/CP-2018-124
Abstract: Abstract. This PAGES (Past Global Changes) 2k (Climate of the past 2000 years Working Group) Special Issue of Climate of the Past brings together the latest understanding of regional change and impacts from PAGES 2k groups across a range of proxies and regions. The Special Issue has emerged from a need to determine the magnitude and rate of change of regional and global climate beyond the timescales accessible within the observational record. This knowledge also plays an important role in attribution studies and is fundamental to understanding the mechanisms and environmental and societal impacts of recent climate change. The scientific studies in the Special Issue reflect the urgent need to better understand regional differences from a truly global view around the PAGES themes of: Climate Variability, Modes and Mechanisms, Methods and Uncertainties and Proxy and Model Understanding.
Impacts of high inter-annual variability of rainfall on a century of extreme hydrologic regime of northwest Australia
Publisher: Copernicus GmbH
Date: 29-04-2015
DOI: 10.5194/HESS-19-2057-2015
Abstract: Abstract. Long-term hydrologic records provide crucial reference baselines of natural variability that can be used to evaluate potential changes in hydrologic regimes and their impacts. However, there is a dearth of studies of the hydrologic regimes for tropical drylands where intraseasonal and interannual variability in magnitude and frequency of precipitation are extreme. Here, we sought to identify the main hydroclimatic determinants of the strongly episodic flood regime of a large catchment in the semi-arid, subtropical northwest of Australia and to establish the background of hydrologic variability for the region over the last century. We used a monthly sequence of satellite images to quantify surface water expression on the Fortescue Marsh, the largest water feature of inland northwest Australia, from 1988 to 2012. We used this sequence together with instrumental rainfall data to build a statistical model with multiple linear regression and reconstruct monthly history of floods and droughts since 1912. We found that severe and intense regional rainfall events, as well as the sequence of recharge events both within and between years, determine surface water expression on the floodplain (i.e. total rainfall, number of rain days and carried-over inundated area R2adj = 0.79 p value 0.001, ERMSP = 56 km2). The most severe reconstructed inundation over the last century was in March 2000 (1000 km2), which is less than the 1300 km2 area required to overflow to the adjacent catchment. The Fortescue Marsh was completely dry for 32% of all years, for periods of up to four consecutive years. Extremely wet years (seven of the 100 years) caused the Marsh to remain inundated for up to 12 months only 25% of years (9% of all months) had floods of greater than 300 km2. The prolonged, severe and consecutive yearly inundations between 1999 and 2006 were unprecedented compared to the last century. While there is high inter-annual variability in the system, if the frequency and intensity of extreme rainfall events for the region were to increase (or be similar to 1999–2006), surface water on the Marsh will become more persistent, in turn impacting its structure and functioning as a wetland.
Pleistocene glacial history of the New Zealand subantarctic islands
Publisher: Copernicus GmbH
Date: 25-05-2018
DOI: 10.5194/CP-2018-52
Abstract: Abstract. The New Zealand subantarctic islands of Auckland and C bell, situated between the Subtropical Front and the Antarctic Convergence in the Pacific sector of the Southern Ocean, provide valuable terrestrial records from a globally-important climatic region. Whilst the islands show clear evidence of past glaciation, the timing and mechanisms behind Pleistocene environmental and climate changes remain uncertain. Here we present a multidisciplinary study of the islands – including marine and terrestrial geomorphological surveys, extensive analyses of sedimentary sequences, a comprehensive dating program, and glacier flowline modelling – to investigate multiple phases of glaciation across the islands. We find evidence that the Auckland Islands hosted a small ice cap at 384,000 ± 26,000 years ago (384 ± 26 ka), most likely during Marine Isotope Stage 10, a period when the Subtropical Front was pushed northwards by seven degrees, and consistent with hemispheric-wide glacial expansion. Despite previous interpretations that suggest the maximum glacial extent occurred in the form of valley glaciation at the Last Glacial Maximum (LGM ~ 21 ka) age, our combined approach suggests minimal LGM glaciation across the New Zealand Subantarctic Islands, and that no glaciers were present during the Antarctic Cold Reversal (ACR ~ 15–13 ka). Instead, our flowline modelling, constrained by field evidence, implies that despite a regional mean annual air temperature depression of ~ 5 °C during the LGM, a combination of high seasonality and low precipitation left the islands incapable of sustaining significant glaciation. We suggest that northwards expansion of winter sea ice during the LGM and subsequent ACR led to precipitation starvation across the mid to high latitudes of the Southern Ocean, resulting in restricted glaciation of the subantarctic islands.
Response to Reviewers Comments (cp-2016-114)
Publisher: Copernicus GmbH
Date: 06-02-2017
Millennial-scale variability in south-east Australian hydroclimate between 30,000 and 10,000 years ago
Publisher: Elsevier BV
Date: 07-2018
Radiocarbon analysis of the early archaeological site of Nauwalabila I, Arnhem Land, Australia: Implications for sample suitability and stratigraphic integrity
Publisher: Elsevier BV
Date: 04-2002
Introgression, hominin dispersal and megafaunal survival in Late Pleistocene Island Southeast Asia
Publisher: Cold Spring Harbor Laboratory
Date: 24-07-2020
DOI: 10.1101/2020.07.24.219048
Abstract: The hominin fossil record of Island Southeast Asia (ISEA) indicates that at least two endemic ‘super-archaic’ species – Homo luzonensis and H. floresiensis – were present around the time anatomically modern humans (AMH) arrived in the region ,000 years ago. Contemporary human populations carry signals consistent with interbreeding events with Denisovans in ISEA – a species that is thought to be more closely related to AMH than the super-archaic endemic ISEA hominins. To query this disparity between fossil and genetic evidence, we performed a comprehensive search for super-archaic introgression in modern human genomes. Our results corroborate widespread Denisovan ancestry in ISEA populations but fail to detect any super-archaic admixture signals. By highlighting local megafaunal survival east of the Wallace Line as a potential signature of deep, pre- H. sapiens hominin-faunal interaction, we propose that this understudied region may hold the key to unlocking significant chapters in Denisovan prehistory.
Brief communication: Impacts of a developing polynya off Commonwealth Bay, East Antarctica, triggered by grounding of iceberg B09B
Publisher: Copernicus GmbH
Date: 04-11-2016
Abstract: Abstract. The dramatic calving of the Mertz Glacier tongue in 2010, precipitated by the movement of iceberg B09B, reshaped the oceanographic regime across the Mertz Polynya and Commonwealth Bay, regions where high-salinity shelf water (HSSW) – the precursor to Antarctic bottom water (AABW) – is formed. Here we present post-calving observations that suggest that this reconfiguration and subsequent grounding of B09B have driven the development of a new polynya and associated HSSW production off Commonwealth Bay. Supported by satellite observations and modelling, our findings demonstrate how local icescape changes may impact the formation of HSSW, with potential implications for large-scale ocean circulation.
Robust estimates of extinction time in the geological record
Publisher: Elsevier BV
Date: 02-2012
Towards a European tephrochronological framework for Termination 1 and the Early Holocene
Publisher: The Royal Society
Date: 15-04-2002
Abstract: The record of deposition of tephras in Europe and the North Atlantic during the period 18.5-8.0 (14)C ka BP (the Last Termination and Early Holocene) is reviewed. Altogether, 34 tephras originating from four main volcanic provinces (Iceland, the Eifel district, the Massif Central and Italy) have been identified so far in geological sequences spanning this time-interval. Most of the records have been based, until very recently, on observations of visible layers of tephras. Here, we report on the potential for extending the areas over which some of the tephras can be traced by the search for layers of micro-tephra, which are not visible to the naked eye, and on the use of geochemical methods to correlate them with known tephra horizons. This approach has greatly extended the area in Northern Europe over which the Vedde Ash can be traced. The same potential exists in southern Europe, which is demonstrated for the first time by the discovery of a distinct layer of micro-tephra of the Neapolitan Yellow Tuff in a site in the Northern Apennines in Italy, far to the north of the occurrences of visible records of this tephra. The paper closes by considering the potential for developing a robust European tephrostratigraphy to underpin the chronology of records of the Last Termination and Early Holocene, thereby promoting a better understanding of the nature, timing and environmental effects of the abrupt climatic changes that characterized this period.
THE APPLICATION OF POLLEN RADIOCARBON DATING AND BAYESIAN AGE-DEPTH MODELING FOR DEVELOPING ROBUST GEOCHRONOLOGICAL FRAMEWORKS OF WETLAND ARCHIVES
Publisher: Cambridge University Press (CUP)
Date: 04-2022
DOI: 10.1017/RDC.2022.29
Abstract: Wetland sediments are valuable archives of environmental change but can be challenging to date. Terrestrial macrofossils are often sparse, resulting in radiocarbon ( 14 C) dating of less desirable organic fractions. An alternative approach for capturing changes in atmospheric 14 C is the use of terrestrial microfossils. We 14 C date pollen microfossils from two Australian wetland sediment sequences and compare these to ages from other sediment fractions (n = 56). For the Holocene Lake Werri Berri record, pollen 14 C ages are consistent with 14 C ages on bulk sediment and humic acids (n = 14), whilst Stable Polycyclic Aromatic Carbon (SPAC) 14 C ages (n = 4) are significantly younger. For Welsby Lagoon, pollen concentrate 14 C ages (n = 21) provide a stratigraphically coherent sequence back to 50 ka BP. 14 C ages from humic acid and µm fractions (n = 13) are inconsistent, and often substantially younger than pollen ages. Our comparison of Bayesian age-depth models, developed in Oxcal, Bacon and Undatable, highlight the strengths and weaknesses of the different programs for straightforward and more complex chrono-stratigraphic records. All models display broad similarities but differences in modeled age-uncertainty, particularly when age constraints are sparse. Intensive dating of wetland sequences improves the identification of outliers and generation of robust age models, regardless of program used.
Anomalous mid-twentieth century atmospheric circulation change over the South Atlantic compared to the last 6000 years
Publisher: IOP Publishing
Date: 06-2016
Implications for the dating of Wisconsinan (Weichselian) Late-glacial events of systematic radiocarbon age differences between terrestrial plant macrofossils from a site in SW Ireland
Publisher: Cambridge University Press (CUP)
Date: 2000
Abstract: AMS radiocarbon dates were obtained from Salix herbacea leaves, Carex seeds, and bulk organic detritus from a lake sediment profile of Wisconsinan (Weichselian) Lateglacial age in SW Ireland. There is a systematic age difference between the dated series from the two types of macrofossils, with ages obtained from Salix herbacea leaves being 900 to 1500 14 C years younger than those obtained from Carex seeds. The latter tend to be more in accord with dates from the total organic detritus in the lake sediment, although the bulk organic fraction invariably registered the older ages. Intact survival of the fragile Salix leaves indicates that they are unlikely to have been physically transferred within the sediment matrix and/or otherwise reworked from the surrounding catchment. Hence, these macrofossils are the more likely to be contemporaneous with the time of deposition. However, there is no significant correlation between measured 14 C age and depth in the Salix values, which scatter over a range of 700 14 C years. In contrast, the age/depth relationship for Carex shows a significant reversal, possibly reflecting the redeposition of these macrofossils, and therefore giving radiocarbon ages that are anomalously old. The data have important implications for the dating of lake sediment sequences by AMS radiocarbon measurement of terrestrial plant macrofossils.
Intensification of Southern Hemisphere westerly winds 2000-1000 years ago: Evidence from the subantarctic Campbell and Auckland Islands (52-50°S)
Publisher: Wiley
Date: 2016
DOI: 10.1002/JQS.2828
Reply to Comment on 'Drought variability in the eastern Australia and New Zealand summer drought atlas (ANZDA, CE 1500-2012) modulated by the Interdecadal Pacific Oscillation'
Publisher: IOP Publishing
Date: 30-05-2017
Delayed maximum northern European summer temperatures during the Last Interglacial as a result of Greenland Ice Sheet melt
Publisher: Geological Society of America
Date: 08-11-2017
DOI: 10.1130/G38402.1
Redating the Global Abrupt Sea-Level Rise during Meltwater Pulse-1A and Implications for Global Ice Mass Loss
Publisher: Copernicus GmbH
Date: 04-03-2021
DOI: 10.5194/EGUSPHERE-EGU21-13669
Abstract: & & & span& Model-based projections of ice-sheet thresholds and global sea-level rise are severely constrained by & /span& & span& instrumental observations being only decadal to century-long. As we improve our understanding of these processes, projections just a few years old are now considered conservative, raising concerns about our ability to successfully plan for abrupt future change. & /span& & span& Past periods of abrupt and extreme warming offer & #8216 rocess analogues& #8217 that can provide new insights into the future rate of response of polar ice sheets to warming of the Earth system. The Last Termination & /span& & span& (20,000-10,000 years ago or 20-10 ka BP) & /span& in the North Atlantic region was characterised by a series of abrupt climatic changes including rapid warming at 14.7 ka BP (the start of the & #8220 B& #248 lling& #8221 , or GI-1 in the Greenland ice-core isotope stratigraphy) which was accompanied by an Antarctic Cold Reversal (ACR) in the south.& Potentially important, during the onset of GI-1, warming persisted in the south for some 256& #177 calendar years before the ACR, providing a period of time during which both polar regions experienced increasing temperatures. Sometime around the onset of GI-1 and the ACR, Meltwater Pulse 1A (MWP-1A) formed an abrupt sea level rise of ~15 metres, and was coincident with a period of enhanced iceberg flux in the Southern Ocean. It seems likely the majority of the sea level rise came from the Northern Hemisphere & #8211 up to 5-6 metres from the Laurentide Ice Sheet & #8211 though the timing remains uncertain. The contribution of Antarctic Ice Sheets (AIS) to global mean sea level (GMSL) rise during MWP-1A range from & #8216 high-end& #8217 scenarios (& m contributing over half of the total GMSL rise), to & #8216 low-end& #8217 (scenarios with little to no contribution). Here we report the results of a multidisciplinary study, with refined age and Antarctic ice-sheet modelling of the MWP-1A sea-level rise. With the recently released international radiocarbon calibration curve (IntCal20), our Bayesian age modelling of terrestrial ages from flooded mangrove sw s suggests global& & span& sea level rose across a mean age range of 14.58 ka BP to 14.42 ka BP, with a mean rate of sea-level rise of 0.94 metres per decade (14.97 metres over 160 years). Because the calibrated age range at 95% confidence overlaps in this age model, it is possible the 15 metre rise during MWP1A could have taken place essentially instantaneously. Even the most conservative age modelling we have undertaken indicates an extraordinary rapid rate of sea-level rise two orders of magnitude larger than the mean rate of global sea level rise since 1993 (0.03& #177 .003 metres per decade). Our ice-sheet modelling suggests a substantial and rapid loss of Antarctic ice mass (mostly from the Weddell Sea Embayment and the Antarctic Peninsula), synchronous with warming and ice loss in the North Atlantic. The drivers and mechanisms of the observed near-synchronous interhemispheric changes will be discussed, with implications for the future.& /span& & / &
Stratigraphy, pollen and 14C dating of Johnston's Gum Hole, a late Quaternary fossil kauri (Agathis australis) site, Northland, New Zealand
Publisher: Wiley
Date: 2009
DOI: 10.1002/JQS.1179
Admixture has obscured signals of historical hard sweeps in humans
Publisher: Springer Science and Business Media LLC
Date: 31-10-2022
DOI: 10.1038/S41559-022-01914-9
Abstract: The role of natural selection in shaping biological ersity is an area of intense interest in modern biology. To date, studies of positive selection have primarily relied on genomic datasets from contemporary populations, which are susceptible to confounding factors associated with complex and often unknown aspects of population history. In particular, admixture between erged populations can distort or hide prior selection events in modern genomes, though this process is not explicitly accounted for in most selection studies despite its apparent ubiquity in humans and other species. Through analyses of ancient and modern human genomes, we show that previously reported Holocene-era admixture has masked more than 50 historic hard sweeps in modern European genomes. Our results imply that this canonical mode of selection has probably been underappreciated in the evolutionary history of humans and suggest that our current understanding of the tempo and mode of selection in natural populations may be inaccurate.
Obliquity control on Southern Hemisphere climate during the last glacial
Publisher: Springer Science and Business Media LLC
Date: 26-06-2015
DOI: 10.1038/SREP11673
Abstract: Recent paleoclimate reconstructions have challenged the traditional view that Northern Hemisphere insolation and associated feedbacks drove synchronous global climate and ice-sheet volume during the last glacial cycle. Here we focus on the response of the Patagonian Ice Sheet and demonstrate that its maximum expansion culminated at 28,400 ± 500 years before present (28.4 ± 0.5 ka), more than 5,000 years before the minima in 65°N summer insolation and the formally-defined Last Glacial Maximum (LGM) at 21,000 ± 2,000 years before present. To investigate the potential drivers of this early LGM (eLGM), we simulate the effects of orbital changes using a suite of climate models incorporating prescribed and evolving sea-ice anomalies. Our analyses suggest that Antarctic sea-ice expansion at 28.5 ka altered the location and intensity of the Southern Hemisphere storm track, triggering regional cooling over Patagonia of 5°C that extends across the wider mid-southern latitudes. In contrast, at the LGM, continued sea-ice expansion reduced regional temperature and precipitation further, effectively starving the ice sheet and resulting in reduced glacial expansion. Our findings highlight the dominant role that orbital changes can play in driving Southern Hemisphere glacial climate via the sensitivity of mid-latitude regions to changes in Antarctic sea-ice extent.
Erratum to Testing the sensitivity of the East Antarctic ice sheet to southern ocean dynamics: Past changes and future implications [Journal of Quaternary Science, 29 91-98]
Publisher: Wiley
Date: 07-2014
DOI: 10.1002/JQS.2700
Supplementary material to "Tropical and mid-latitude forcing of continental Antarctic temperatures"
Publisher: Copernicus GmbH
Date: 30-07-2015
Response to Comment on Abrupt warming events drove Late Pleistocene Holarctic megafaunal turnover
Publisher: American Association for the Advancement of Science (AAAS)
Date: 26-02-2016
Abstract: Rasmussen and Svensson correctly point out that there is currently no satisfactory method to fully align the Greenland and Cariaco Basin records of climate change. However, our approach using interstadial onsets as tie-points allows direct comparison between radiocarbon dates and Greenland climate records. Crucially, both the standard Greenland and the merged Greenland-Cariaco time scales show that interstadial warming was associated with megafaunal genetic transitions.
Climate variations in Britain during the last Glacial-Holocene transition (15.0-11.5 cal ka BP): Comparison with the GRIP ice-core record
Publisher: Geological Society of London
Date: 03-1999
Greenland ice mass loss during the Younger Dryas driven by Atlantic Meridional Overturning Circulation feedbacks
Publisher: Springer Science and Business Media LLC
Date: 09-08-2018
DOI: 10.1038/S41598-018-29226-8
Abstract: Understanding feedbacks between the Greenland Ice Sheet (GrIS) and the Atlantic Meridional Overturning Circulation (AMOC) is crucial for reducing uncertainties over future sea level and ocean circulation change. Reconstructing past GrIS dynamics can extend the observational record and elucidate mechanisms that operate on multi-decadal timescales. We report a highly-constrained last glacial vertical profile of cosmogenic isotope exposure ages from Sermilik Fjord, a marine-terminating ice stream in the southeast sector of the GrIS. Our reconstruction reveals substantial ice-mass loss throughout the Younger Dryas (12.9-11.7 ka), a period of marked atmospheric and sea-surface cooling. Earth-system modelling reveals that southern GrIS marginal melt was likely driven by strengthening of the Irminger Current at depth due to a weakening of the AMOC during the Younger Dryas. This change in North Atlantic circulation appears to have drawn warm subsurface waters to southeast Greenland despite markedly cooler sea surface temperatures, enhancing thermal erosion at the grounding lines of palaeo ice-streams, supporting interpretation of regional marine-sediment cores. Given current rates of GrIS meltwater input into the North Atlantic and the vulnerability of major ice streams to water temperature changes at the grounding line, this mechanism has important implications for future AMOC changes and northern hemisphere heat transport.
Aboriginal mitogenomes reveal 50,000 years of regionalism in Australia
Publisher: Springer Science and Business Media LLC
Date: 08-03-2017
DOI: 10.1038/NATURE21416
Abstract: Aboriginal Australians represent one of the longest continuous cultural complexes known. Archaeological evidence indicates that Australia and New Guinea were initially settled approximately 50 thousand years ago (ka) however, little is known about the processes underlying the enormous linguistic and phenotypic ersity within Australia. Here we report 111 mitochondrial genomes (mitogenomes) from historical Aboriginal Australian hair s les, whose origins enable us to reconstruct Australian phylogeographic history before European settlement. Marked geographic patterns and deep splits across the major mitochondrial haplogroups imply that the settlement of Australia comprised a single, rapid migration along the east and west coasts that reached southern Australia by 49-45 ka. After continent-wide colonization, strong regional patterns developed and these have survived despite substantial climatic and cultural change during the late Pleistocene and Holocene epochs. Remarkably, we find evidence for the continuous presence of populations in discrete geographic areas dating back to around 50 ka, in agreement with the notable Aboriginal Australian cultural attachment to their country.
Climate, people and faunal succession on Java, Indonesia
Publisher: Elsevier BV
Date: 07-2008
A global mean sea-surface temperature dataset for the Last Interglacial (129–116 kyr) and contribution of thermal expansion to sea-level change
Publisher: Copernicus GmbH
Date: 29-01-2020
Abstract: Abstract. A valuable analogue for assessing Earth’s sensitivity to warming is the Last Interglacial (LIG 129–116 kyr), when global temperatures (0−+2 °C) and mean sea level (+6–11 m) were higher than today. The direct contribution of warmer conditions to global sea level (thermosteric) are uncertain. We report here a global network of LIG sea surface temperatures (SST) obtained from various published temperature proxies (e.g. faunal/floral assemblages, Mg/Ca ratios of calcareous plankton, alkenone UK’37). Each reconstruction is averaged across the LIG (anomalies relative to 1981–2010), corrected for ocean drift and with varying seasonality (189 annual, 99 December-February, and 92 June–August records). We summarise the current limitations of SST reconstructions for the LIG and the spatial temperature features of a naturally warmer world. Because of local δ18O seawater changes, uncertainty in the age models of marine cores, and differences in s ling resolution and/or sedimentation rates, the reconstructions are restricted to mean conditions. To avoid bias towards in idual LIG SSTs based on only a single (and potentially erroneous) measurement or a single interpolated data point, here we average across the entire LIG. To investigate the sensitivity of the reconstruction to high temperatures, we also report maximum values during the first 5 ka of the LIG (129–124 kyr). The global dataset provides a remarkably coherent pattern of higher SST increases at polar latitudes than in the tropics, with comparable estimates between different SST proxies. We report mean global annual SST anomalies of 0.2 ± 0.1 °C and a maximum of 0.9 ± 0.2 °C respectively. Using the reconstructed SSTs suggests a mean thermosteric sea level rise of 0.01 ± 0.1 m and a maximum of 0.13 ± 0.1 m respectively. The data provide an important natural baseline for a warmer world, constraining the contributions of Greenland and Antarctic ice sheets to global sea level during a geographically widespread expression of high sea level, and can be used to test the next inter-comparison of models for projecting future climate change. The dataset described in this paper, including summary temperature and thermosteric sea-level reconstructions, are available at 0.1594/PANGAEA.904381 (Turney et al., 2019).
The impact of the giant iceberg B09B on population size and breeding success of Adélie penguins in Commonwealth Bay, Antarctica
Publisher: Cambridge University Press (CUP)
Date: 02-02-2016
DOI: 10.1017/S0954102015000644
Abstract: The arrival of iceberg B09B in Commonwealth Bay, East Antarctica, and subsequent fast ice expansion has dramatically increased the distance Adélie penguins ( Pygoscelis adeliae ) breeding at Cape Denison must travel in search of food. This has provided a natural experiment to investigate the impact of iceberg stranding events and sea ice expansion along the East Antarctic coast. As part of the Australasian Antarctic Expedition 2013–14, the Adélie penguin colony at Cape Denison was censused to compare to historic counts. Whilst some 5520 pairs still bred at Cape Denison there has been an order of magnitude decline in Adélie numbers in the area in comparison to the first counts a century ago and, critically, recent estimates based on satellite images and a census in 1997. In contrast, an Adélie population on the eastern fringe of Commonwealth Bay just 8 km from the fast ice edge was thriving, indicating the arrival of B09B and fast ice expansion was probably responsible for the observed recent population decline. In conclusion, the Cape Denison population could be extirpated within 20 years unless B09B relocates or the now perennial fast ice within the bay breaks out. Our results have important implications for wider East Antarctic if the current increasing sea ice trend continues.
Tree-ring radiocarbon reveals reduced solar activity during Younger Dryas cooling
Publisher: Copernicus GmbH
Date: 23-03-2020
DOI: 10.5194/EGUSPHERE-EGU2020-11654
Abstract: & & The Younger Dryas stadial (YD) was a return to glacial-like conditions in the North Atlantic region that interrupted deglacial warming around 12900 cal BP (before 1950 AD). Terrestrial and marine records suggest this event was initiated by the interruption of deep-water formation arising from North American freshwater runoff, but the causes of the millennia-long duration remain unclear. To investigate the solar activity, a possible YD driver, we exploit the cosmic production signals of tree-ring radiocarbon (& sup& & /sup& C) and ice-core beryllium-10 (& sup& & /sup& Be). Here we present the highest temporally resolved dataset of & sup& & /sup& C measurements (n = 1558) derived from European tree rings that have been accurately extended back to 14226 cal BP (& #177 , 2-& #963 ), allowing precise alignment of ice-core records across this period. We identify a substantial increase in & sup& & /sup& C and & sup& & /sup& Be production starting at 12780 cal BP is comparable in magnitude to the historic Little Ice Age, being a clear sign of grand solar minima. We hypothesize the timing of the grand solar minima provides a significant lifying factor leading to the harsh sustained glacial-like conditions seen in the YD.& &
Response to review
Publisher: Copernicus GmbH
Date: 12-02-2019
Response to comment
Publisher: Copernicus GmbH
Date: 12-02-2019
Decadal-scale onset and termination of Antarctic ice-mass loss during the last deglaciation
Publisher: Copernicus GmbH
Date: 03-03-2021
DOI: 10.5194/EGUSPHERE-EGU21-3385
Abstract: & & Emerging evidence suggests retreat of the Antarctic Ice Sheet (AIS) can persist considerably longer than the duration of the forcing. Unfortunately, the short observational record cannot resolve the tipping points, rate of change, and responses on century and longer timescales. New data from Iceberg Alley identifies eight retreat phases after the last Ice Age that de-stabilized the AIS within a decade, contributing to global sea-level rise for centuries to a millennium, which subsequently stabilized equally rapidly. New blue ice records and independent ice-sheet modeling demonstrate the dynamic response of the AIS included a step-wise retreat of up to 400& km across the Ross Sea, accompanied by ice elevation drawdown of the West Antarctic Ice Sheet (& & m). Together, these long time series support studies that propose the recent acceleration of AIS mass loss may mark the beginning of a prolonged period of ice sheet retreat, associated with substantial global sea level rise.& &
Abrupt warming events drove Late Pleistocene Holarctic megafaunal turnover
Publisher: American Association for the Advancement of Science (AAAS)
Date: 07-08-2015
Abstract: The causes of the Pleistocene extinctions of large numbers of megafaunal species in the Northern Hemisphere remain unclear. A range of evidence points to human hunting, climate change, or a combination of both. Using ancient DNA and detailed paleoclimate data, Cooper et al. report a close relationship between Pleistocene megafaunal extinction events and rapid warming events at the start of interstadial periods. Their analysis strengthens the case for climate change as the key driver of megafaunal extinctions, with human impacts playing a secondary role. Science , this issue p. 602
Geochronology of cave deposits at Liang Bua and of adjacent river terraces in the Wae Racang valley, western Flores, Indonesia
Publisher: Elsevier BV
Date: 11-2009
DOI: 10.1016/J.JHEVOL.2009.01.003
Abstract: A robust timeframe for the extant cave deposits at Liang Bua, and for the river terraces in the adjoining Wae Racang valley, is essential to constrain the period of existence and time of extinction of Homo floresiensis and other biota that have been excavated at this hominin type locality. Reliable age control is also required for the variety of artifacts excavated from these deposits, and to assist in environmental reconstructions for this river valley and for the region more broadly. In this paper, we summarize the available geochronological information for Liang Bua and its immediate environs, obtained using seven numerical-age methods: radiocarbon, thermoluminescence, optically- and infrared-stimulated luminescence (collectively known as optical dating), uranium-series, electron spin resonance, and coupled electron spin resonance/uranium-series. We synthesize the large number of numerical age determinations reported previously and present additional age estimates germane to questions of hominin evolution and extinction.
Progress in refining the global radiocarbon calibration curve using New Zealand kauri (Agathis australis) tree-ring series from Oxygen Isotope Stage 3
Publisher: Elsevier BV
Date: 04-2015
Palaeoecological signatures of vegetation change induced by herbivory regime shifts on subantarctic Enderby Island
Publisher: Elsevier BV
Date: 02-2016
Retreat of the Antarctic Ice Sheet During the Last Interglaciation and Implications for Future Change
Publisher: American Geophysical Union (AGU)
Date: 29-08-2021
DOI: 10.1029/2021GL094513
Abstract: The Antarctic Ice Sheet (AIS) response to past warming consistent with the 1.5–2°C “safe limit” of the United Nations Paris Agreement is currently not well known. Empirical evidence from the most recent comparable period, the Last Interglaciation, is sparse, and transient ice‐sheet experiments are few and inconsistent. Here, we present new, transient, GCM‐forced ice‐sheet simulations validated against proxy reconstructions. This is the first time such an evaluation has been attempted. Our empirically constrained simulations indicate that the AIS contributed 4 m to global mean sea level by 126 ka BP, with ice lost primarily from the Amundsen, but not Ross or Weddell Sea, sectors. We resolve the conflict between previous work and show that the AIS thinned in the Wilkes Subglacial Basin but did not retreat. We also find that the West AIS may be predisposed to future collapse even in the absence of further environmental change, consistent with previous studies.
Using technology to direct learning in higher education: The way forward?
Publisher: SAGE Publications
Date: 03-2009
Abstract: Improvements in technology appear to provide an unprecedented opportunity to improve learning and teaching within the higher education system. At present, however, opinions are ided over the efficacy of such an approach and the extent to which technology should be embraced in teaching. Over a period of two years, we have developed a new `blended' module where all learning resources are provided online and formal teaching sessions are used to provide the directed learning needed by students. This article explores the effectiveness of using technology to direct learning and identifies generic problems. Using measures of student performance, we demonstrate that technology in higher education can significantly improve student learning when fully aligned to the teaching aims and fully embedded within a module. The ability of students to use technology to repeatedly return to resources was a clear benefit, allowing students to take responsibility for their own study at a pace appropriate for the learner.
Widespread dispersal of Icelandic tephra: How does the Eyjafjöll eruption of 2010 compare to past Icelandic events?
Publisher: Wiley
Date: 29-06-2010
DOI: 10.1002/JQS.1421
Abstract: The Eyjafjöll AD 2010 eruption is an extraordinary event in that it led to widespread and unprecedented disruption to air travel over Europe – a region generally considered to be free from the hazards associated with volcanic eruptions. Following the onset of the eruption, satellite imagery demonstrated the rapid transportation of ash by westerly winds over mainland Europe, eventually expanding to large swathes of the North Atlantic Ocean and the eastern seaboard of Canada. This small‐to‐intermediate size eruption and the dispersal pattern observed are not particularly unusual for Icelandic eruptions within a longer‐term perspective. Indeed, the Eyjafjöll eruption is a relatively modest eruption in comparison to some of the 20 most voluminous eruptions that have deposited cryptotephra in sedimentary archives in mainland Europe, such as the mid Younger Dryas Vedde Ash and the mid Holocene Hekla 4 tephra. The 2010 eruption, however, highlights the critical role that weather patterns play in the distribution of a relatively small amount of ash and also highlights the spatially complex dispersal trajectories of tephra in the atmosphere. Whether or not the preservation of the Eyjafjöll 2010 tephra in European proxy archives will correspond to the extensive distributions mapped in the atmosphere remains to be seen. The Eyjafjöll 2010 event highlights our increased vulnerability to natural hazards rather than the unparalleled explosivity of the event. Copyright © 2010 John Wiley & Sons, Ltd.
Marine biomarkers from ice cores reveal enhanced high-latitude Southern Ocean carbon sink during the Antarctic Cold Reversal
Publisher: California Digital Library (CDL)
Date: 24-05-2019
Supplementary material to "Do Southern Hemisphere tree rings record past volcanic events?"
Publisher: Copernicus GmbH
Date: 17-12-2021
Does the Agulhas Current amplify global temperatures during super-interglacials?
Publisher: Wiley
Date: 25-08-2010
DOI: 10.1002/JQS.1423
The INTegration of Ice core, MArine and TErrestrial records of the last termination (INTIMATE)60,000 to 8000 BP
Publisher: Elsevier BV
Date: 03-2012
Tropical forcing of increased Southern Ocean climate variability revealed by a 140-year subantarctic temperature reconstruction
Publisher: Copernicus GmbH
Date: 15-03-2017
Abstract: Abstract. Occupying about 14 % of the world's surface, the Southern Ocean plays a fundamental role in ocean and atmosphere circulation, carbon cycling and Antarctic ice-sheet dynamics. Unfortunately, high interannual variability and a dearth of instrumental observations before the 1950s limits our understanding of how marine–atmosphere–ice domains interact on multi-decadal timescales and the impact of anthropogenic forcing. Here we integrate climate-sensitive tree growth with ocean and atmospheric observations on southwest Pacific subantarctic islands that lie at the boundary of polar and subtropical climates (52–54° S). Our annually resolved temperature reconstruction captures regional change since the 1870s and demonstrates a significant increase in variability from the 1940s, a phenomenon predating the observational record. Climate reanalysis and modelling show a parallel change in tropical Pacific sea surface temperatures that generate an atmospheric Rossby wave train which propagates across a large part of the Southern Hemisphere during the austral spring and summer. Our results suggest that modern observed high interannual variability was established across the mid-twentieth century, and that the influence of contemporary equatorial Pacific temperatures may now be a permanent feature across the mid- to high latitudes.
Tropical and mid-latitude forcing of continental Antarctic temperatures
Publisher: Copernicus GmbH
Date: 21-12-2015
Abstract: Abstract. Future changes in atmospheric circulation and associated modes of variability are a major source of uncertainty in climate projections. Nowhere is this issue more acute than across the mid-latitudes to high latitudes of the Southern Hemisphere (SH), which over the last few decades have experienced extreme and regionally variable trends in precipitation, ocean circulation and temperature, with major implications for Antarctic ice melt and surface mass balance. Unfortunately there is a relative dearth of observational data, limiting our understanding of the driving mechanism(s). Here we report a new 130-year annually resolved record of δD – a proxy for temperature – from the geographic South Pole where we find a significant influence from extratropical pressure anomalies which act as "gatekeepers" to the meridional exchange of air masses. Reanalysis of global atmospheric circulation suggests these pressure anomalies play a significant influence on mid- to high-latitude SH climate, modulated by the tropical Pacific Ocean. This work adds to a growing body of literature confirming the important roles of tropical and mid-latitude atmospheric circulation variability on Antarctic temperatures. Our findings suggest that future increasing tropical warmth will strengthen meridional circulation, exaggerating current trends, with potentially significant impacts on Antarctic surface mass balance.
Supplementary material to "Brief Communication: Evidence of a developing Polynya off Commonwealth Bay, East Antarctica, triggered by grounding of iceberg"
Publisher: Copernicus GmbH
Date: 07-03-2016
Detection of Lateglacial distal tephra layers in the Netherlands
Publisher: Wiley
Date: 05-2005
IntCal13 and Marine13 radiocarbon age calibration curves 0-50,000 years cal BP
Publisher: Cambridge University Press (CUP)
Date: 2013
DOI: 10.2458/AZU_JS_RC.55.16947
Abstract: The IntCal09 and Marine09 radiocarbon calibration curves have been revised utilizing newly available and updated data sets from 14 C measurements on tree rings, plant macrofossils, speleothems, corals, and foraminifera. The calibration curves were derived from the data using the random walk model (RWM) used to generate IntCal09 and Marine09, which has been revised to account for additional uncertainties and error structures. The new curves were ratified at the 21st International Radiocarbon conference in July 2012 and are available as Supplemental Material at www.radiocarbon.org. The database can be accessed at intcal.qub.ac.uk/intcal13/.
Why didn't they ask Evans?
Publisher: Cambridge University Press (CUP)
Date: 09-2017
DOI: 10.1017/S0032247417000468
Abstract: Arguably the best known scientific Antarctic venture was the British Antarctic Expedition of 1911–1913 led by Captain Robert Falcon Scott. Whilst the so-called race to the geographic South Pole with Roald Amundsen's Norwegian Antarctic expedition excited international interest, the tragic death of Scott and his returning Polar Party was a striking reminder of the hazards of operating in the south. Recent work has highlighted the possible role expedition second-in-command Lieutenant Edward ‘Teddy’ Evans played in the deaths of Scott and his men. Here I report newly discovered documents which, when placed in a wider context, raise significant questions over Evans’ behaviour during the expedition. The evidence focuses on the shortage of food at key depots, the apparently deliberate obfuscation of when Evans fell down with scurvy and the failure to pass on orders given by Scott. It is concluded that Evans actions on and off the ice can at best be described as ineffectual, at worst deliberate sabotage. Why Evans was not questioned more about these events on his return to England remains unknown.
Volcanic ash deposition and long-term vegetation change on subantarctic Marion Island
Publisher: Informa UK Limited
Date: 08-2007
Catchment instability and Asian summer monsoon variability during the early Holocene in southwestern China
Publisher: Wiley
Date: 24-10-2013
High-precision dating and correlation of ice, marine and terrestrial sequences spanning Heinrich Event 3: Testing mechanisms of interhemispheric change using New Zealand ancient kauri (Agathis australis)
Publisher: Elsevier BV
Date: 04-2016
Visual and fluorescence characterisation of particulate aerosols in ice cores with imaging flow cytometry
Publisher: Copernicus GmbH
Date: 23-03-2020
DOI: 10.5194/EGUSPHERE-EGU2020-9607
Abstract: & & Current efforts to examine and quantify so-called & #8216 biomarkers& #8217 present in polar ice s les offer exciting potential as biological and biochemical proxies for past climate and ocean dynamics. Here we present a new rapid and easily replicable method to provide measurements of the microscopic particulate content of ice s les from polar environments. Using an Amnis& #174 Imagestream& #174 Imaging Flow Cytometer, melted snow and ice s les from Patriot Hills in the Ellsworth Mountains, Antarctica were analysed for their particulate (biological and non-biological) content. Selective use of a nucleic acid stain pre-treatment allows for a straightforward gating strategy that resolves both autofluorescent and non-autofluorescent biological material in s le replicates. In the Patriot Hills s les this method clearly identifies marine picoplankton, along with non-biological particulates such as tephra and minerogenic material. Crucially, the 60x Brightfield images provided by the Imagestream offer a significant additional capability above standard flow cytometry systems each object identified by the machine can be visually differentiated (automatically or manually) from particulates with similar fluorescence properties. Back-trajectory analysis with the NOAA Hybrid Single-Particle Lagrangian Integrated Trajectory (HySPLIT) model indicates that these ice-bound marine organisms originate from the Weddell and Amundsen-Bellingshausen Seas. This technique, when paired with established chemical and biochemical methods, shows considerable potential in providing valuable information about the nature and origin of aerosols and biomarker signals trapped in past ice layers.& &
Late-surviving megafauna in Tasmania, Australia, implicate human involvement in their extinction
Publisher: Proceedings of the National Academy of Sciences
Date: 26-08-2008
Abstract: Establishing the cause of past extinctions is critical if we are to understand better what might trigger future occurrences and how to prevent them. The mechanisms of continental late Pleistocene megafaunal extinction, however, are still fiercely contested. Potential factors contributing to their demise include climatic change, human impact, or some combination. On the Australian mainland, 90% of the megafauna became extinct by ≈46 thousand years (ka) ago, soon after the first archaeological evidence for human colonization of the continent. Yet, on the neighboring island of Tasmania (which was connected to the mainland when sea levels were lower), megafaunal extinction appears to have taken place before the initial human arrival between 43 and 40 ka, which would seem to exonerate people as a contributing factor in the extirpation of the island megafauna. Age estimates for the last megafauna, however, are poorly constrained. Here, we show, by direct dating of fossil remains and their associated sediments, that some Tasmanian megafauna survived until at least 41 ka (i.e., after their extinction on the Australian mainland) and thus overlapped with humans. Furthermore, a vegetation record for Tasmania spanning the last 130 ka shows that no significant regional climatic or environmental change occurred between 43 and 37 ka, when a land bridge existed between Tasmania and the mainland. Our results are consistent with a model of human-induced extinction for the Tasmanian megafauna, most probably driven by hunting, and they reaffirm the value of islands adjacent to continental landmasses as tests of competing hypotheses for late Quaternary megafaunal extinctions.
Temperature, Wind, Cloud, and the Postglacial Tree Line History of Sub-Antarctic Campbell Island
Publisher: MDPI AG
Date: 07-11-2019
DOI: 10.3390/F10110998
Abstract: C bell Island, which is 600 km south of New Zealand, has the southernmost tree line in this ocean sector. Directly under the maximum of the westerlies, the island is sensitive to changes in wind strength and direction. Pollen records from three peat cores spanning the tree line ecotone provide a 17,000-year history of vegetation change, temperature, and site moisture. With postglacial warming, tundra was replaced by tussock grassland 12,500 years ago. A subsequent increase of shrubland was reversed at 10,500 years ago and wetland-grassland communities became dominant. Around 9000 years ago, trees spread, with maximum tree line elevation reached around 6500 to 3000 years ago. This sequence is out of step with Southern Ocean sea surface temperatures, which were warmer than 12,500 to 9000 years ago, and, subsequently, cooled. C bell Island tree lines were decoupled from temperature trends in the adjacent ocean by weaker westerlies from 12,500 to 9000 years ago, which leads to the intrusion of warmer, cloudier northern airmasses. This reduced solar radiation and evapotranspiration while increasing atmospheric humidity and substrate wetness, which suppressed tree growth. Cooler, stronger westerlies in the Holocene brought clearer skies, drier air, increased evapotranspiration, and rising tree lines. Future global warming will not necessarily lead to rising tree lines in oceanic regions.
Response to comments on 'Does the Agulhas Current amplify global temperatures during super-interglacials?'
Publisher: Wiley
Date: 11-2011
DOI: 10.1002/JQS.1556
A new and less destructive laboratory procedure for the physical separation of distal glass tephra shards from sediments
Publisher: Elsevier BV
Date: 09-2005
Global Peak in Atmospheric Radiocarbon Provides a Potential Definition for the Onset of the Anthropocene Epoch in 1965
Publisher: Springer Science and Business Media LLC
Date: 19-02-2018
DOI: 10.1038/S41598-018-20970-5
Abstract: Anthropogenic activity is now recognised as having profoundly and permanently altered the Earth system, suggesting we have entered a human-dominated geological epoch, the ‘Anthropocene’. To formally define the onset of the Anthropocene, a synchronous global signature within geological-forming materials is required. Here we report a series of precisely-dated tree-ring records from C bell Island (Southern Ocean) that capture peak atmospheric radiocarbon ( 14 C) resulting from Northern Hemisphere-dominated thermonuclear bomb tests during the 1950s and 1960s. The only alien tree on the island, a Sitka spruce ( Picea sitchensis ), allows us to seasonally-resolve Southern Hemisphere atmospheric 14 C, demonstrating the ‘bomb peak’ in this remote and pristine location occurred in the last-quarter of 1965 (October-December), coincident with the broader changes associated with the post-World War II ‘Great Acceleration’ in industrial capacity and consumption. Our findings provide a precisely-resolved potential Global Stratotype Section and Point (GSSP) or ‘golden spike’, marking the onset of the Anthropocene Epoch.
Unprecedented High Northern Australian Streamflow Linked to an Intensification of the Indo‐Australian Monsoon
Publisher: American Geophysical Union (AGU)
Date: 03-2022
DOI: 10.1029/2021WR030881
Abstract: Streamflow in Australia’s northern rivers has been steadily increasing since the 1970s, most likely due to increased intensity in the Indo‐Australian monsoon. However, because of limited data availability, it is hard to assess this recent trend and therefore contextualize potential future climatic changes. In this study, we used a network of 63 precipitation‐sensitive tree‐ring chronologies from the Indo‐Australian and Asian monsoon regions to reconstruct streamflow in the Daly catchment in the Northern Territory of Australia from 1413 to 2005 CE. We used a novel wavelet‐based method to transform the variance structure of the tree‐ring chronologies to better match the hydroclimate prior to reconstruction with a hierarchical Bayesian regression model. Our streamflow reconstruction accounts for 72%–78% of the variance in the instrumental period and closely matches both historical flood events and independent proxy records, increasing confidence in its validity. We find that while streamflow has been increasing since the 1800s, the most recent 40‐year period is unprecedented in the last ∼600 years. Comparison to an independent coral‐based streamflow record shows regional coherency in this trend. Extreme high flows were found to be linked to La Niña events, but we found no significant relationship between streamflow and El Niño events, or streamflow and other regional climatic drivers. More work is therefore needed to understand the drivers of the recent streamflow increase, but, regardless of the cause, water managers should be aware of the paleoclimatic context before making decisions on water allocations.
Selection and treatment of data for radiocarbon calibration: An update to the international calibration (IntCal) criteria
Publisher: Cambridge University Press (CUP)
Date: 2013
DOI: 10.2458/AZU_JS_RC.55.16955
Abstract: High-quality data from appropriate archives are needed for the continuing improvement of radiocarbon calibration curves. We discuss here the basic assumptions behind 14 C dating that necessitate calibration and the relative strengths and weaknesses of archives from which calibration data are obtained. We also highlight the procedures, problems, and uncertainties involved in determining atmospheric and surface ocean 14 C/ 12 C in these archives, including a discussion of the various methods used to derive an independent absolute timescale and uncertainty. The types of data required for the current IntCal database and calibration curve model are tabulated with ex les.
Changes in fire regimes since the Last Glacial Maximum: an assessment based on a global synthesis and analysis of charcoal data
Publisher: Springer Science and Business Media LLC
Date: 14-12-2007
A continental narrative: Human settlement patterns and Australian climate change over the last 35,000 years
Publisher: Elsevier BV
Date: 09-2015
Do Southern Hemisphere tree rings record past volcanic events? A case study from New Zealand
Publisher: Copernicus GmbH
Date: 24-05-2022
Abstract: Abstract. Much of our knowledge about the impacts of volcanic eruptions on climate comes from proxy records. However, little is known about their impact on the low to mid-latitudes of the Southern Hemisphere. Using superposed epoch analysis, we investigated whether volcanic signals could be identified in annual tree-ring series from eight New Zealand dendrochronological species. We found that most species are reliable recorders of volcanic cooling and that the magnitude and persistence of the post-event response can be broadly linked to plant life history traits. Across species, site-based factors, particularly altitude and exposure to prevailing conditions, are more important determinants of the strength of the volcanic response than species. We then investigated whether chronology selection impacts the magnitude of post-volcanic cooling in tree-ring-based temperature reconstructions by developing two new multispecies reconstructions of New Zealand summer (December–February) temperature with one reconstruction from the pool of all available chronologies, and the other from a selected subset shown to be sensitive to volcanic eruptions. Both reconstructions record temperature anomalies that are remarkably consistent with studies based on instrumental temperature and the ensemble mean response of climate models, demonstrating that New Zealand ring widths are reliable indicators of regional volcanic climate response. However, we also found that volcanic response can be complex, with positive, negative, and neutral responses identified – sometimes within the same species group. Species-wide composites thus tend to underestimate the volcanic response. This has important implications for the development of future tree-ring and multiproxy temperature reconstructions from the Southern Hemisphere.
Holocene Demographic Changes and the Emergence of Complex Societies in Prehistoric Australia
Publisher: Public Library of Science (PLoS)
Date: 17-06-2015
Holocene climatic change and past Irish societal response
Publisher: Elsevier BV
Date: 2006
Evidence for increased expression of the Amundsen Sea Low over the South Atlantic during the late Holocene
Publisher: Copernicus GmbH
Date: 03-2018
DOI: 10.5194/CP-2018-11
Abstract: Abstract. The Amundsen Sea Low (ASL) plays a major role in modulating the climate and environment of Antarctica and is of global importance in the Earth system. Unfortunately, a relative dearth of observational data across the Amundsen and Bellingshausen Seas prior to the satellite era (post-1979) limits our understanding of past behaviour and impact of the ASL. The limited proxy evidence for changes in the ASL are primarily limited to the Antarctic where ice core evidence suggests a deepening of the atmospheric pressure system during the late Holocene. However, no data has previously been reported from the northern side of the ASL. Here we report a high-resolution, multi-proxy study of a 5000 year-long peat record from the Falkland Islands (South Atlantic sector of the Southern Ocean), an area sensitive to contemporary ASL dynamics. In combination with climate reanalysis, we find a marked period of wetter, colder conditions most likely the result of enhanced southerly airflow between 5000 and 2500 years ago, and inconsistent with synoptic conditions associated with the ASL today. After 2500 years ago, drier and warmer conditions were established, implying more westerly airflow and the increased projection of the ASL onto the South Atlantic. Our results are in agreement with Antarctic ice core records and suggest the Falkland Islands provide a valuable location for reconstructing atmospheric circulation changes across a large sector of the Southern Ocean on multi-decadal to millennial timescales. The possible role of tropical Pacific in establishing contemporary-like synoptic circulation is explored.
The discovery of New Zealand's oldest shipwreck - possible evidence of further Dutch exploration of the South Pacific
Publisher: Elsevier BV
Date: 02-2014
Uncertainties in dating constrain model choice for inferring extinction time from fossil records
Publisher: Elsevier BV
Date: 03-2015
Supplementary material to "Tropical forcing of increased Southern Ocean climate variability revealed by a 140-year subantarctic temperate reconstruction"
Publisher: Copernicus GmbH
Date: 21-11-2016
Antarctic ice sheet discharge driven by atmosphere-ocean feedbacks at the Last Glacial Termination
Publisher: Springer Science and Business Media LLC
Date: 05-01-2017
DOI: 10.1038/SREP39979
Abstract: Reconstructing the dynamic response of the Antarctic ice sheets to warming during the Last Glacial Termination (LGT 18,000–11,650 yrs ago) allows us to disentangle ice-climate feedbacks that are key to improving future projections. Whilst the sequence of events during this period is reasonably well-known, relatively poor chronological control has precluded precise alignment of ice, atmospheric and marine records, making it difficult to assess relationships between Antarctic ice-sheet (AIS) dynamics, climate change and sea level. Here we present results from a highly-resolved ‘horizontal ice core’ from the Weddell Sea Embayment, which records millennial-scale AIS dynamics across this extensive region. Counterintuitively, we find AIS mass-loss across the full duration of the Antarctic Cold Reversal (ACR 14,600–12,700 yrs ago), with stabilisation during the subsequent millennia of atmospheric warming. Earth-system and ice-sheet modelling suggests these contrasting trends were likely Antarctic-wide, sustained by feedbacks lified by the delivery of Circumpolar Deep Water onto the continental shelf. Given the anti-phase relationship between inter-hemispheric climate trends across the LGT our findings demonstrate that Southern Ocean-AIS feedbacks were controlled by global atmospheric teleconnections. With increasing stratification of the Southern Ocean and intensification of mid-latitude westerly winds today, such teleconnections could lify AIS mass loss and accelerate global sea-level rise.
Interpreting vegetation change in tropical arid ecosystems from sediment molecular fossils and their stable isotope compositions: A baseline study from the Pilbara region of northwest Australia
Publisher: Elsevier BV
Date: 10-2016
Tropical forcing of increased Southern Ocean climate variability revealed by a 140-year subantarctic temperate reconstruction
Publisher: Copernicus GmbH
Date: 21-11-2016
DOI: 10.5194/CP-2016-114
Abstract: Abstract. Occupying 14% of the world’s surface, the Southern Ocean plays a fundamental role in global climate, ocean circulation, carbon cycling and Antarctic ice-sheet stability. Unfortunately, high interannual variability and a dearth of instrumental observations before the 1950s limits our understanding of how marine-atmosphere-ice domains interact on multi-decadal timescales and the impact of anthropogenic forcing. Here we integrate climate-sensitive tree growth with ocean and atmospheric observations on southwest Pacific subantarctic islands that lie at the boundary of polar and subtropical climates (52–54˚S). Our annually-resolved temperature reconstruction captures regional change since the 1870s and demonstrates a significant increase in variability from the mid-twentieth century, a phenomenon predating the observational record. Climate reanalysis and modelling shows a parallel change in tropical Pacific sea surface temperatures that generate an atmospheric Rossby wave train which propagates across a large part of the Southern Hemisphere during the austral spring and summer.
Global temperature and hydroclimate in warmer climates of the past and future: the Last Interglacial versus greenhouse scenarios
Publisher: Copernicus GmbH
Date: 04-03-2021
DOI: 10.5194/EGUSPHERE-EGU21-15417
Abstract: & & Past climates contain precious information about the workings of the climate system, and about what can be expected in a changed climate. The Last Interglacial (LIG ca. 125,000 years ago) is the most recent period of climate warmer than modern, at least in the Northern Hemisphere. Because of this, it has been often proposed that the LIG holds a partial analogy with a future warmer climate forced by enhanced greenhouse effect. Still, such analogy has never been examined in a quantitative manner. Here we address the question: for which scenario, time horizon, regions and season is the climate of the LIG a useful analogue of the future? We use the results of 13 climate models that performed the standard experiments of PMIP4 and CMIP6, and present a comparison of hemispheric temperature and precipitation between the LIG and SSP scenarios of the future. We also two independent assessments of models performance, by comparing their temperature and precipitation to climate reanalysis of the last decades and to proxies of the LIG. Insights gained from this comparison can inform studies in disciplines beyond climate studies, such as hydrology and ecology.& &
Phases of peatland carbon accumulation in the southern mid-latitudes
Publisher: Copernicus GmbH
Date: 28-03-2022
DOI: 10.5194/EGUSPHERE-EGU22-12232
Abstract: & & Creating high resolution chronologies in sediment sequences is important for understanding past carbon-climate dynamics, including accurately dating the timing of climate events, and calculating carbon accumulation changes through time. Here we present & & sup& & /sup& C dates from UNSWs high-throughput MICADAS (Turney et al. 2021) that help answer key questions about carbon-climate dynamics in the Southern Hemisphere. Peatlands from the southern mid-high latitudes have an important role in the global carbon budget but are underrepresented in global syntheses due to paucity of data. Developing accurate age-depth models from peat sequences is notoriously difficult. Outliers are common, with peat being susceptible to issues such as root penetration and in-wash of sediment. With careful consideration to site selection (Thomas et al. 2019) and material preparation (e.g. sieving out root and rootlet material), the age-depth models presented here demonstrate stratigraphic integrity with no evidence of significant outliers, providing robust and detailed chronologies to enable a range of scientific questions to be answered.& & & & To better constrain the understanding of southern peatland dynamics, we collected and radiocarbon-dated 25 basal peats from across sub-Antarctic islands of the South Atlantic region, doubling the existing available data. We then collated basal peat radiocarbon ages from & & #176 S and analysed their temporal and spatial distribution. We find two distinct phases of peat formation, at ~16,000 cal years BP and ~13,000 cal years BP, independent of northern hemisphere peat growth. Well-constrained age models from these regions (including a 6 m peat sequence with 55 & sup& & /sup& C dates) show changes in carbon accumulation rates that are consistent with these phases. Potential drivers of these phases include growth disruption via the Antarctic Cold Reversal, and the latitudinal movement of the southern hemisphere westerly winds, with implications for future carbon storage in these under-studied regions.& & & & & & & & & & strong& References& /strong& & & & & Thomas, Z.A., Turney, C.S.M., Hogg, A., Williams, A.N., Fogwill, C.J., 2019. Investigating Subantarctic 14 C Ages of Different Peat Components: Site and S le Selection for Developing Robust Age Models in Dynamic Landscapes. Radiocarbon 61, 1& #8211 . doi:10.1017/rdc.2019.54& & & & Turney, C., Becerra-Val ia, L., Sookdeo, A., Thomas, Z.A., Palmer, J., Haines, H.A., Cadd, H., Wacker, L., Baker, A., Anderson, M., Jacobsen, G., Meredith, K., Chinu, K., Bollhalder, S., Marjo, C., 2021. Radiocarbon protocols and first intercomparison results from the Chronos 14Carbon-Cycle Facility, University of New South Wales, Sydney, Australia. Radiocarbon 63(3), 1003& #8211 . doi:10.1017/RDC.2021.23& &
Deriving a consistent delta13C signature from tree canopy leaf material for palaeoclimatic reconstruction
Publisher: Wiley
Date: 08-2002
Long-term ecology resolves the timing, region of origin and process of establishment for a disputed alien tree
Publisher: Oxford University Press (OUP)
Date: 2015
A global multiproxy database for temperature reconstructions of the Common Era
Publisher: Springer Science and Business Media LLC
Date: 11-07-2017
Abstract: Reproducible climate reconstructions of the Common Era (1 CE to present) are key to placing industrial-era warming into the context of natural climatic variability. Here we present a community-sourced database of temperature-sensitive proxy records from the PAGES2k initiative. The database gathers 692 records from 648 locations, including all continental regions and major ocean basins. The records are from trees, ice, sediment, corals, speleothems, documentary evidence, and other archives. They range in length from 50 to 2000 years, with a median of 547 years, while temporal resolution ranges from biweekly to centennial. Nearly half of the proxy time series are significantly correlated with HadCRUT4.2 surface temperature over the period 1850–2014. Global temperature composites show a remarkable degree of coherence between high- and low-resolution archives, with broadly similar patterns across archive types, terrestrial versus marine locations, and screening criteria. The database is suited to investigations of global and regional temperature variability over the Common Era, and is shared in the Linked Paleo Data (LiPD) format, including serializations in Matlab, R and Python.
Robust expression of ENSO throughout the Last Interglacial
Publisher: Copernicus GmbH
Date: 23-03-2020
DOI: 10.5194/EGUSPHERE-EGU2020-12812
Abstract: & & The El Ni& #241 o-Southern Oscillation (ENSO) is a driver of global atmosphere-ocean dynamics, but projections of frequency and magnitude in different climate states remain uncertain. Palaeoclimate records offer the potential to improve our understanding of ENSO behaviour but most are fragmentary, suffer low resolution, and/or typically do not cover periods warmer than present day. The Last Interglacial (129-116 kyr BP) was the most recent period during which global temperatures were close to 21st century projections, and potentially provides insights into operation of climate modes of variability in the future. Here we report a continuous, inter-annually resolved record of hydroclimate spanning 220-80 ka from Lynch& #8217 s Crater in tropical northeast Australia, a region highly sensitive to ENSO. Our reconstruction is based on a micro-X-ray fluorescence (XRF)-generated elemental profile at 200 & #181 m resolution, combined with loss-on-ignition, magnetic susceptibility, and pollen analysis. We find that during globally warmer periods (including super-interglacial Stage 5e, and 5c), there are significantly larger litudes in high-frequency ENSO spectral range (3-8 years), which are absent from the record during the glacial stages MIS6 and MIS4. Our results imply an ENSO dependence on mean climate, with enhanced ENSO variance during interglacials globally warmer than present. These results are consistent with climate model projections for a future slowdown of the Walker circulation and more extreme El Ni& #241 o events under greenhouse warming.& &
A 1300-year reconstruction of the South Pacific Convergence Zone using a Pacific-wide tree-ring network
Publisher: Copernicus GmbH
Date: 23-03-1970
DOI: 10.5194/EGUSPHERE-EGU2020-11844
Abstract: & & The South Pacific Convergence Zone (SPCZ) is the largest driver of precipitation variability over South Pacific island communities during the austral warm season influencing the severity and duration of drought and the frequency of tropical cyclones. The SPCZ is known to exhibit variability on a range of timescales, from intra-seasonal to multidecadal variations, modulated by the Interdecadal Pacific Oscillation (IPO). Despite its climatic and societal importance, determining the causes of low frequency variability in the SPCZ has been h ered by the short instrumental data record, with most comprehensive analyses since the satellite era. Here we report the first paleoclimate reconstruction of the SPCZ, allowing climate variability in the South Pacific region to be explored back to 700 CE. Our 1300-year reconstruction of the SPCZI (South Pacific Convergence Zone Index the difference between mean sea level pressure between Apia, Samoa and Suva, Fiji) is based on a trans-Pacific network of precisely dated tree-ring proxies. Capturing SPCZ teleconnections from both sides of the Pacific has produced a robust, unbiased reconstruction with excellent reconstruction skill over the entire period. El Ni& #241 o-Southern Oscillation periodicities (& #8764 -7 years) are pervasive throughout the SPCZI reconstruction. Multidecadal periodicities wax and wane, apparently coinciding with the timing of the Medieval Climate Anomaly (c. 1000-1200 CE) and Little Ice Age (1300-1700 CE). We discuss some of the drivers of SPCZI variability including global dimming events. Our reconstruction helps improve our understanding of past hydroclimatic behaviour in the southwest Pacific and can be used to validate general circulation model projections for Pacific Island communities in the twenty-first century.& &
Continental-scale temperature variability during the past two millennia
Publisher: Springer Science and Business Media LLC
Date: 21-04-2013
DOI: 10.1038/NGEO1797
Non-uniform interhemispheric temperature trends over the past 550 years
Publisher: Springer Science and Business Media LLC
Date: 28-03-2010
Contrasting Northern and Southern Hemisphere Temperature Variations During Last Millennium
Publisher: Elsevier BV
Date: 11-2012
Ancient human genomes reveal a hidden history of strong selection in Eurasia
Publisher: Cold Spring Harbor Laboratory
Date: 03-04-2020
DOI: 10.1101/2020.04.01.021006
Abstract: The role of natural selection in shaping biological ersity is an area of intense interest in modern biology. To date, studies of positive selection have primarily relied upon genomic datasets from contemporary populations, which are susceptible to confounding factors associated with complex and often unknown aspects of population history. In particular, admixture between erged populations can distort or hide prior selection events in modern genomes, though this process is not explicitly accounted for in most selection studies despite its apparent ubiquity in humans and other species. Through analyses of ancient and modern human genomes, we show that previously reported Holocene-era admixture has masked more than 50 historic hard sweeps in modern European genomes. Our results imply that this canonical mode of selection has likely been underappreciated in the evolutionary history of humans and suggests that our current understanding of the tempo and mode of selection in natural populations may be quite inaccurate.
The IntCal20 Northern Hemisphere Radiocarbon Age Calibration Curve (0–55 cal kBP)
Publisher: Cambridge University Press (CUP)
Date: 08-2020
DOI: 10.1017/RDC.2020.41
Abstract: Radiocarbon ( 14 C) ages cannot provide absolutely dated chronologies for archaeological or paleoenvironmental studies directly but must be converted to calendar age equivalents using a calibration curve compensating for fluctuations in atmospheric 14 C concentration. Although calibration curves are constructed from independently dated archives, they invariably require revision as new data become available and our understanding of the Earth system improves. In this volume the international 14 C calibration curves for both the Northern and Southern Hemispheres, as well as for the ocean surface layer, have been updated to include a wealth of new data and extended to 55,000 cal BP. Based on tree rings, IntCal20 now extends as a fully atmospheric record to ca. 13,900 cal BP. For the older part of the timescale, IntCal20 comprises statistically integrated evidence from floating tree-ring chronologies, lacustrine and marine sediments, speleothems, and corals. We utilized improved evaluation of the timescales and location variable 14 C offsets from the atmosphere (reservoir age, dead carbon fraction) for each dataset. New statistical methods have refined the structure of the calibration curves while maintaining a robust treatment of uncertainties in the 14 C ages, the calendar ages and other corrections. The inclusion of modeled marine reservoir ages derived from a three-dimensional ocean circulation model has allowed us to apply more appropriate reservoir corrections to the marine 14 C data rather than the previous use of constant regional offsets from the atmosphere. Here we provide an overview of the new and revised datasets and the associated methods used for the construction of the IntCal20 curve and explore potential regional offsets for tree-ring data. We discuss the main differences with respect to the previous calibration curve, IntCal13, and some of the implications for archaeology and geosciences ranging from the recent past to the time of the extinction of the Neanderthals.
Introduction to the special issue “Climate of the past 2000 years: regional and trans-regional syntheses”
Publisher: Copernicus GmbH
Date: 29-03-2019
Abstract: Abstract. This PAGES (Past Global Changes) 2k (climate of the past 2000 years working group) special issue of Climate of the Past brings together the latest understanding of regional change and impacts from PAGES 2k groups across a range of proxies and regions. The special issue has emerged from a need to determine the magnitude and rate of change of regional and global climate beyond the timescales accessible within the observational record. This knowledge also plays an important role in attribution studies and is fundamental to understanding the mechanisms and environmental and societal impacts of recent climate change. The scientific studies in the special issue reflect the urgent need to better understand regional differences from a truly global view around the PAGES themes of “Climate Variability, Modes and Mechanisms”, “Methods and Uncertainties”, and “Proxy and Model Understanding”.
Obliquity-driven expansion of North Atlantic sea ice during the last glacial
Publisher: American Geophysical Union (AGU)
Date: 10-12-2015
DOI: 10.1002/2015GL066344
500-year reconstruction of Dez River discharge in southwestern Iran from tree rings
Publisher: Elsevier BV
Date: 09-2023
A global environmental crisis 42,000 years ago
Publisher: American Association for the Advancement of Science (AAAS)
Date: 19-02-2021
Abstract: Do terrestrial geomagnetic field reversals have an effect on Earth's climate? Cooper et al. created a precisely dated radiocarbon record around the time of the Lasch s geomagnetic reversal about 41,000 years ago from the rings of New Zealand sw kauri trees. This record reveals a substantial increase in the carbon-14 content of the atmosphere culminating during the period of weakening magnetic field strength preceding the polarity switch. The authors modeled the consequences of this event and concluded that the geomagnetic field minimum caused substantial changes in atmospheric ozone concentration that drove synchronous global climate and environmental shifts. Science , this issue p. 811
The geochemical characterization and correlation of Late Holocene tephra layers at Ambra Crater and Kuk Swamp, Papua New Guinea
Publisher: Wiley
Date: 09-2009
DOI: 10.1002/GJ.1164
Looking back from the future
Publisher: Springer Science and Business Media LLC
Date: 04-12-2008
Estimating past leaf-to-air vapour pressure deficit from terrestrial plant δ13C
Publisher: Wiley
Date: 08-1999
DOI: 10.1002/(SICI)1099-1417(199908)14:5<437::AID-JQS458>3.0.CO;2-Z
Tree rings show recent high summer-autumn precipitation in northwest Australia is unprecedented within the last two centuries
Publisher: Public Library of Science (PLoS)
Date: 03-06-2015
Vedde ash layer discovered in a small lake basin on the Scottish mainland
Publisher: Geological Society of London
Date: 07-1997
Does the El Niño-Southern Oscillation control the interhemispheric radiocarbon offset?
Publisher: Cambridge University Press (CUP)
Date: 2007
DOI: 10.1016/J.YQRES.2006.08.008
Abstract: Since the 1970s it has been recognised that Southern Hemisphere s les have a lower radiocarbon content than contemporaneous material in the Northern Hemisphere. This interhemispheric radiocarbon offset has traditionally been considered to be the result of a greater surface area in the southern ocean and high-latitude deepwater formation. This is despite the fact that the El Niño–Southern Oscillation (ENSO) is known to play a significant role in controlling the interannual variability of atmospheric carbon dioxide by changing the flux of ‘old’ CO 2 from the tropical Pacific. Here we demonstrate that over the past millennium, the Southern Hemisphere radiocarbon offset is characterised by a pervasive 80-yr cycle with a step shift in mean values coinciding with the transition from the Medieval Warm Period to the Little Ice Age. The observed changes suggest an ENSO-like role in influencing the interhemispheric radiocarbon difference, most probably modulated by the Interdecadal Pacific Oscillation, and supports a tropical role in forcing centennial-scale global climate change.
Punctuated Shutdown of Atlantic Meridional Overturning Circulation during Greenland Stadial 1
Publisher: Springer Science and Business Media LLC
Date: 19-05-2016
DOI: 10.1038/SREP25902
Abstract: The Greenland Stadial 1 (GS-1 ~12.9 to 11.65 kyr cal BP) was a period of North Atlantic cooling, thought to have been initiated by North America fresh water runoff that caused a sustained reduction of North Atlantic Meridional Overturning Circulation (AMOC), resulting in an antiphase temperature response between the hemispheres (the ‘bipolar seesaw’). Here we exploit sub-fossil New Zealand kauri trees to report the first securely dated, decadally-resolved atmospheric radiocarbon ( 14 C) record spanning GS-1. By precisely aligning Southern and Northern Hemisphere tree-ring 14 C records with marine 14 C sequences we document two relatively short periods of AMOC collapse during the stadial, at ~12,920-12,640 cal BP and 12,050-11,900 cal BP. In addition, our data show that the interhemispheric atmospheric 14 C offset was close to zero prior to GS-1, before reaching ‘near-modern’ values at ~12,660 cal BP, consistent with synchronous recovery of overturning in both hemispheres and increased Southern Ocean ventilation. Hence, sustained North Atlantic cooling across GS-1 was not driven by a prolonged AMOC reduction but probably due to an equatorward migration of the Polar Front, reducing the advection of southwesterly air masses to high latitudes. Our findings suggest opposing hemispheric temperature trends were driven by atmospheric teleconnections, rather than AMOC changes.
Interpreting stable-isotope records from freshwater snail-shell carbonate: A Holocene case study from Lake Gölhisar, Turkey
Publisher: SAGE Publications
Date: 07-2002
DOI: 10.1191/0959683602HL564RR
Abstract: The oxygen and carbon stable-isotope ratios from fossil snail shells within a small intramontane lake in southwest Turkey are used to highlight the potential, and problems, of using freshwater snail carbonate as a palaeoenvironmental proxy. Two species (Gyraulus piscinarum and Valvata cristata) yielded different isotope ratios at the same s ling intervals, probably due to differences in water-isotope composition between different microhabitats. Isotope ratios from a number of in idual shells from the same s ling intervals (representing 7–25 years), show large ranges (up to 8‰ for 18O) for each species. Only by analysis of a significant number of species-specific shells (5) from each s ling interval can a true understanding of environmental change be obtained. Averages of the data provide an insight into longer-term climatic variation while the ranges provide an estimate of short-term (decadal) environmental variability.
Tropical and mid-latitude forcing of continental Antarctic temperatures
Publisher: Copernicus GmbH
Date: 30-07-2015
Abstract: Abstract. Future changes in atmospheric circulation and associated modes of variability are a major source of uncertainty in climate projections. Nowhere is this issue more acute than across the mid- to high-latitudes of the Southern Hemisphere (SH) which over the last few decades has experienced extreme and regional variable trends in precipitation, ocean circulation, and temperature, with major implications for Antarctic ice melt and surface mass balance. Unfortunately there is a relative dearth of observational data, limiting our understanding of the driving mechanism(s). Here we report a new 130-year annually-resolved record of δ D – a proxy for temperature – from the South Geographic Pole where we find a significant influence from extra-tropical pressure anomalies which act as "gatekeepers" to the meridional exchange of air masses. Reanalysis of global atmospheric circulation suggests these pressure anomalies play a considerably larger influence on mid- to high-latitude SH climate than hitherto believed, modulated by the tropical Pacific Ocean. Our findings suggest that future increasing tropical warmth will strengthen meridional circulation, exaggerating current trends, with potentially significant impacts on Antarctic surface mass balance.
Dating ancient wood by high-sensitivity liquid scintillation counting and accelerator mass spectrometry-Pushing the boundaries
Publisher: Elsevier BV
Date: 12-2006
Human-environment interactions in Australian drylands: Exploratory time-series analysis of archaeological records
Publisher: SAGE Publications
Date: 05-2008
Abstract: Exploratory time-series analysis of radiocarbon data from archaeological contexts is used to reconstruct the population history of arid Australia, allowing this to be read in concert with records of climatic variability over the last 20 000 years. Probability distribution plots of 971 radiocarbon ages from 286 sites in five dryland regions (the arid west coast, Pilbara and Murchison, Nullarbor, arid interior and the southeastern arid zone) provide a proxy record of prehistoric population fluctuations in these areas. There is regional variation, but the radiocarbon density plots suggest a step-wise pattern of population growth and expansion, with significant thresholds at 19, 8 and 1.5 cal. kyr BP. Within this, the plots suggest a saw-tooth pattern of rapid population growth and decline on a 1—3 kyr frequency, with a marked collapse of dryland hunter-gatherer populations around 3—2.5 cal. kyr BP affecting most regions. Comparison with climate data shows broad correlations with past temperature and rainfall variability, sea-level change and ENSO activity, but the interaction of prehistoric populations and these environmental changes is not well resolved. High litude environmental changes appear to have triggered stadial changes in population, rather than smooth transitions. Dryland populations may also have become more sensitive to small environmental changes in the late Holocene, as population density increased. A large increase in population around 1.5 cal. kyr BP is associated with small changes in regional palaeoecology, which are not otherwise represented in palaeoclimatic data sets. Spectral analysis identifies two cyclical periodicities of 1340 and 175 years within the population histories, also suggesting responses to millennial and submillennial climatic variability, a pattern most marked in the late Holocene.
Site preferences in hetero-metallic [Fe9−xNix] clusters: a combined crystallographic, spectroscopic and theoretical analysis
Publisher: Royal Society of Chemistry (RSC)
Date: 2017
DOI: 10.1039/C7DT02930F
Abstract: The distribution of Fe( ii ) and Ni( ii ) over two distinct metal sites in [Fe 9−x Ni x ] clusters is studied by X-ray crystallography, Mössbauer and XRF spectroscopies, and DFT calculations.
Assessing the continuity of the blue ice climate record at Patriot Hills, Horseshoe Valley, West Antarctica
Publisher: American Geophysical Union (AGU)
Date: 02-03-2016
DOI: 10.1002/2015GL066476
Catastrophic early Holocene sea level rise, human migration and the Neolithic transition in Europe
Publisher: Elsevier BV
Date: 09-2007
Climate change scenarios for Great Britain and Europe
Publisher: Elsevier
Date: 1995
The Adams Event, a geomagnetic-driven environmental crisis 42,000 years ago
Publisher: Copernicus GmbH
Date: 23-03-2020
DOI: 10.5194/EGUSPHERE-EGU2020-12314
Abstract: & & & strong& Geological archives record multiple reversals of Earth& #8217 s magnetic poles, yet the potential impacts of these events remain unknown. The lack of any obvious association between the last major inversion, the Lasch s Excursion ~41 thousand years ago (ka), and polar ice paleoclimate records has underpinned the view that geomagnetic reversals do not have major environmental consequences. We find this is not the case. Importantly, the weakened geomagnetic field causes rapid production of atmospheric radiocarbon, and the lack of accurate calibration records has complicated dating of environmental and archaeological events in other parts of the world. Here we exploit the first detailed record of radiocarbon levels across the Lasch s Excursion using New Zealand sw kauri (& em& Agathis australis& /em& ) trees to precisely align Pacific Basin environmental changes with polar paleoclimate records (via& & sup& & /sup& Be). Comprehensive radiocarbon-dated and glacial sequences are consistent with global chemistry climate modelling, and show synchronous climate changes across the mid to low latitudes that are concentrated during the geomagnetic field minima (42.2-41.5 ka) in the transitional phase that precedes the Lasch s Excursion. Critically, the revised timing reveals associations with a wide range of extinction events and major changes in the global archaeological record, which we hereby term the Adams Event. The climatic, environmental, and evolutionary impacts of past magnetic reversals now form a critical issue for future investigation.& /strong& & &
Geochemical characterization of Quaternary tephras from the Campanian Province, Italy
Publisher: Elsevier BV
Date: 02-2008
Redating the onset of burning of Lynch's Crater (North Queensland): Implications for human settlement in Australia
Publisher: Wiley
Date: 2001
DOI: 10.1002/JQS.643
A global mean sea surface temperature dataset for the Last Interglacial (129–116 ka) and contribution of thermal expansion to sea level change
Publisher: Copernicus GmbH
Date: 10-12-2020
DOI: 10.5194/ESSD-12-3341-2020
Abstract: Abstract. A valuable analogue for assessing Earth's sensitivity to warming is the Last Interglacial (LIG 129–116 ka), when global temperatures (0 to +2 ∘C) and mean sea level (+6 to 11 m) were higher than today. The direct contribution of warmer conditions to global sea level (thermosteric) is uncertain. We report here a global network of LIG sea surface temperatures (SST) obtained from various published temperature proxies (e.g. faunal and floral plankton assemblages, Mg ∕ Ca ratios of calcareous organisms, and alkenone U37K′). We summarize the current limitations of SST reconstructions for the LIG and the spatial temperature features of a naturally warmer world. Because of local δ18O seawater changes, uncertainty in the age models of marine cores, and differences in s ling resolution and/or sedimentation rates, the reconstructions are restricted to mean conditions. To avoid bias towards in idual LIG SSTs based on only a single (and potentially erroneous) measurement or a single interpolated data point, here we report average values across the entire LIG. Each site reconstruction is given as an anomaly relative to 1981–2010, corrected for ocean drift, and where available seasonal estimates are provided (189 annual, 99 December–February, and 92 June–August records). To investigate the sensitivity of the reconstruction to high temperatures, we also report maximum values during the first 5 millennia of the LIG (129–124 ka). We find mean global annual SST anomalies of 0.2 ± 0.1 ∘C averaged across the LIG and an early maximum peak of 0.9 ± 0.1 ∘C, respectively. The global dataset provides a remarkably coherent pattern of higher SST increases at polar latitudes than in the tropics (demonstrating the polar lification of surface temperatures during the LIG), with comparable estimates between different proxies. Polewards of 45∘ latitude, we observe annual SST anomalies averaged across the full LIG of 0.8 ± 0.3 ∘C in both hemispheres with an early maximum peak of 2.1 ± 0.3 ∘C. Using the reconstructed SSTs suggests a mean LIG global thermosteric sea level rise of 0.08 ± 0.1 m and a peak contribution of 0.39 ± 0.1 m, respectively (assuming warming penetrated to 2000 m depth). The data provide an important natural baseline for a warmer world, constraining the contributions of Greenland and Antarctic ice sheets to global sea level during a geographically widespread expression of high sea level, and can be used to test the next inter-comparison of models for projecting future climate change. The dataset described in this paper, including summary temperature and thermosteric sea level reconstructions, is available at 0.1594/PANGAEA.904381 (Turney et al., 2019).
Brief Communication: Evidence of a developing Polynya off Commonwealth Bay, East Antarctica, triggered by grounding of iceberg
Publisher: Copernicus GmbH
Date: 07-03-2016
DOI: 10.5194/TC-2016-19
Abstract: Abstract. The dramatic calving of the Mertz Glacier Tongue in 2010, triggered by the impact of iceberg B09B, reshaped the oceanographic regime across the Mertz Polynya and Commonwealth Bay, regions where high salinity shelf water (HSSW) is formed, the precursor to Antarctic bottom water (AABW). Here we compare post-calving observations with high-resolution ocean modelling which suggest that this reconfiguration has led to the development of a new polynya off Commonwealth Bay, where HSSW production continues by the grounding of B09B. Our findings demonstrate how local changes in icescape can impact formation of AABW, with implications for large-scale ocean circulation and climate.
Decadally Resolved Lateglacial Radiocarbon Evidence from New Zealand Kauri
Publisher: Cambridge University Press (CUP)
Date: 24-10-2016
DOI: 10.1017/RDC.2016.86
Abstract: The Last Glacial–Interglacial Transition (LGIT 15,000–11,000 cal BP) was characterized by complex spatiotemporal patterns of climate change, with numerous studies requiring accurate chronological control to decipher leads from lags in global paleoclimatic, paleoenvironmental, and archaeological records. However, close scrutiny of the few available tree-ring chronologies and radiocarbon-dated sequences composing the IntCal13 14 C calibration curve indicates significant weakness in 14 C calibration across key periods of the LGIT. Here, we present a decadally resolved atmospheric 14 C record derived from New Zealand kauri spanning the Lateglacial from ~13,100–11,365 cal BP. Two floating kauri 14 C time series, curve-matched to IntCal13, serve as a 14 C backbone through the Younger Dryas. The floating Northern Hemisphere (NH) 14 C data sets derived from the YD-B and Central European Lateglacial Master tree-ring series are matched against the new kauri data, forming a robust NH 14 C time series to ~14,200 cal BP. Our results show that IntCal13 is questionable from ~12,200–11,900 cal BP and the ~10,400 BP 14 C plateau is approximately 5 decades too short. The new kauri record and repositioned NH pine 14 C series offer a refinement of the international 14 C calibration curves IntCal13 and SHCal13, providing increased confidence in the correlation of global paleorecords.
North European last glacial-interglacial transition (LGIT; 15-9 ka) tephrochronology: Extended limits and new events
Publisher: Wiley
Date: 2006
DOI: 10.1002/JQS.990
Ocean currents generate large footprints in marine palaeoclimate proxies
Publisher: Springer Science and Business Media LLC
Date: 04-03-2015
DOI: 10.1038/NCOMMS7521
Abstract: Fossils of marine microorganisms such as planktic foraminifera are among the cornerstones of palaeoclimatological studies. It is often assumed that the proxies derived from their shells represent ocean conditions above the location where they were deposited. Planktic foraminifera, however, are carried by ocean currents and, depending on the life traits of the species, potentially incorporate distant ocean conditions. Here we use high-resolution ocean models to assess the footprint of planktic foraminifera and validate our method with proxy analyses from two locations. Results show that foraminifera, and thus recorded palaeoclimatic conditions, may originate from areas up to several thousands of kilometres away, reflecting an ocean state significantly different from the core site. In the eastern equatorial regions and the western boundary current extensions, the offset may reach 1.5 °C for species living for a month and 3.0 °C for longer-living species. Oceanic transport hence appears to be a crucial aspect in the interpretation of proxy signals.
Testing the sensitivity of the East Antarctic Ice Sheet to Southern Ocean dynamics: past changes and future implications
Publisher: Wiley
Date: 26-12-2014
DOI: 10.1002/JQS.2683
Southern Ocean carbon sink enhanced by sea-ice feedbacks at the Antarctic Cold Reversal
Publisher: Springer Science and Business Media LLC
Date: 22-06-2020
DEVELOPMENT OF THE INTCAL DATABASE
Publisher: Cambridge University Press (CUP)
Date: 28-07-2023
DOI: 10.1017/RDC.2023.53
Abstract: The IntCal family of radiocarbon ( 14 C) calibration curves is based on research spanning more than three decades. The IntCal group have collated the 14 C and calendar age data (mostly derived from primary publications with other types of data and meta-data) and, since 2010, made them available for other sorts of analysis through an open-access database. This has ensured transparency in terms of the data used in the construction of the ratified calibration curves. As the IntCal database expands, work is underway to facilitate best practice for new data submissions, make more of the associated metadata available in a structured form, and help those wishing to process the data with programming languages such as R, Python, and MATLAB. The data and metadata are complex because of the range of different types of archives. A restructured interface, based on the “IntChron” open-access data model, includes tools which allow the data to be plotted and compared without the need for export. The intention is to include complementary information which can be used alongside the main 14 C series to provide new insights into the global carbon cycle, as well as facilitating access to the data for other research applications. Overall, this work aims to streamline the generation of new calibration curves.
One Thousand Three Hundred Years of Variability in the Position of the South Pacific Convergence Zone
Publisher: American Geophysical Union (AGU)
Date: 25-08-2020
DOI: 10.1029/2020GL088238
Abstract: The South Pacific Convergence Zone (SPCZ) is the largest rain belt in the Southern Hemisphere and a key driver of precipitation variability, impacting South Pacific island communities. Our millennial‐long reconstruction is based on a trans‐Pacific tree‐ring network, containing chronologies sensitive to changes in the SPCZ because of its pervasive nature, spatial extent, and link to the El Niño‐Southern Oscillation. The reconstruction explains 58% of variance in the instrumental SPCZ index from 1911–1998. El Niño‐Southern Oscillation cycles are identified throughout the reconstruction period. Multidecadal periodicities wax and wane, coinciding with a sustained eastward shift during the Medieval Climate Anomaly (~1,000–1,200 CE). We find large volcanic eruptions increased the tendency for the SPCZ to be displaced eastward. The reconstruction helps improve our understanding of past hydroclimatic behavior in the southwest Pacific and can be used to validate general circulation model projections for Pacific Island communities and the wider region in the 21st century.
The Eltanin asteroid impact: Possible South Pacific palaeomegatsunami footprint and potential implications for the Pliocene-Pleistocene transition
Publisher: Wiley
Date: 03-09-2012
DOI: 10.1002/JQS.2571
Palaeoceanography of the western Pacific and marginal seas
Publisher: Wiley
Date: 12-2009
DOI: 10.1002/JQS.1362
Early warnings and missed alarms for abrupt monsoon transitions
Publisher: Copernicus GmbH
Date: 13-04-2015
Abstract: Abstract. Palaeo-records from China (Cheng et al., 2009 Wang et al., 2008, 2001) demonstrate the East Asian Summer Monsoon (EASM) is dominated by abrupt and large magnitude monsoon shifts on millennial timescales, switching between periods of high and weak monsoon rains. It has been hypothesised that over these timescales, the EASM exhibits two stable states with bifurcation-type tipping points between them (Schewe et al., 2012). Here we test this hypothesis by looking for early warning signals of past bifurcations in speleothem records from Sanbao Cave and Hulu Cave, China (Wang et al., 2008, 2001), spanning the penultimate glacial cycle, and in multiple model simulations derived from the data. We find hysteresis behaviour in our model simulations with transitions directly forced by solar insolation. We detect critical slowing down prior to an abrupt monsoon shift during the penultimate deglaciation consistent with long-term orbital forcing. However, such signals are only detectable when the change in system stability is sufficiently slow to be detected by the s ling resolution of the dataset, raising the possibility that the alarm was missed and a similar forcing drove earlier EASM shifts.
Elemental δ13C at Allen's Cave, Nullarbor Plain, Australia: Assessing post-depositional disturbance and reconstructing past environments
Publisher: Wiley
Date: 2001
DOI: 10.1002/JQS.633
A 250-year periodicity in Southern Hemisphere westerly winds over the last 2600 years
Publisher: Copernicus GmbH
Date: 03-02-2016
Abstract: Abstract. Southern Hemisphere westerly airflow has a significant influence on the ocean–atmosphere system of the mid- to high latitudes with potentially global climate implications. Unfortunately, historic observations only extend back to the late 19th century, limiting our understanding of multi-decadal to centennial change. Here we present a highly resolved (30-year) record of past westerly wind strength from a Falkland Islands peat sequence spanning the last 2600 years. Situated within the core latitude of Southern Hemisphere westerly airflow (the so-called furious fifties), we identify highly variable changes in exotic pollen and charcoal derived from South America which can be used to inform on past westerly air strength. We find a period of high charcoal content between 2000 and 1000 cal. years BP, associated with increased burning in Patagonia, most probably as a result of higher temperatures and stronger westerly airflow. Spectral analysis of the charcoal record identifies a pervasive ca. 250-year periodicity that is coherent with radiocarbon production rates, suggesting that solar variability has a modulating influence on Southern Hemisphere westerly airflow. Our results have important implications for understanding global climate change through the late Holocene.
Why didn't they ask Evans?: a response to Karen May
Publisher: Cambridge University Press (CUP)
Date: 03-2018
DOI: 10.1017/S0032247418000220
Abstract: In ’Why didn't they ask Evans?’ (Turney, 2017), I draw together previously unpublished sources and new analyses of published material to cast further light on the circumstances that led to the fatal events surrounding the return of Captain Robert Falcon Scott's Polar Party on the British Antarctic Expedition (BAE, 1911–1913). Of particular importance are the notes on the meeting between the Royal Geographical Society's President Lord Curzon and the widows Kathleen Scott and Oriana Wilson in April 1913, which explicitly identify Lieutenant Edward ‘Teddy’ Evans as having removed food that exceeded his allocation as a member of the Last Supporting Party (Curzon, 1913), the establishment and almost immediate closure of a ‘Committee of Enquiry’ chaired by Lord Curzon (Beaumont, 1913a, b, c Cherry-Garrard, 1913a Darwin, 1913 Goldie, 1913), the recognition of missing food at key depots by the returning Polar Party on the 7, 24 and 27 February 1912 (Scott, 1913a Wilson, 1912), Evans’ anger at not being selected as a member of the Polar Party and his early departure home (Evans, 1912), the revised timeline of when Evans fell down with scurvy on the Ross Ice Shelf to apparently align with when and where the food was removed ( The Advertiser , 3 April 1912, Adelaide: 10) (Cherry-Garrard, 1922 Ellis, 1969 Evans, 1912, 1913a, 1943 Lashly, 1912 Scott, 1913a, 1913b), Evans’ failure to ensure Scott's orders regarding the return of the dog sledging teams had been acted on (Cherry-Garrard, 1922 Gran, 1961 Hattersley-Smith & McGhie, 1984) and the misunderstanding amongst senior Royal Geographical Society members during Evans’ recuperation in the UK that Apsley Cherry-Garrard ‘was to meet the South Pole party, with two teams of dogs, at the foot of the [Beardmore] glacier’ (Markham, 1913). I would like to thank May (2018) for her comment and acknowledge that Edward Wilson's sketchbooks of the expedition's logistics, scientific priorities, sketches and notes on the BAE comprise entries from 1911–1912 and not solely from 1912, which Turney (2017) used to denote the year of the last entry.
Was there a '4.2ka event' in Great Britain and Ireland? Evidence from the peatland record
Publisher: Elsevier BV
Date: 2014
The characterization and significance of a MIS 5a distal tephra on mainland Australia
Publisher: Elsevier BV
Date: 09-2009
Technical note: Optimizing the utility of combined GPR, OSL, and Lidar (GOaL) to extract paleoenvironmental records and decipher shoreline evolution
Publisher: Copernicus GmbH
Date: 28-02-2221
Abstract: Abstract. Records of past sea levels, storms, and their impacts on coastlines are crucial for forecasting and managing future changes resulting from anthropogenic global warming. Coastal barriers that have prograded over the Holocene preserve within their accreting sands a history of storm erosion and changes in sea level. High-resolution geophysics, geochronology, and remote sensing techniques offer an optimal way to extract these records and decipher shoreline evolution. These methods include light detection and ranging (lidar) to image the lateral extent of relict shoreline dune morphology in 3-D, ground-penetrating radar (GPR) to record paleo-dune, beach, and nearshore stratigraphy, and optically stimulated luminescence (OSL) to date the deposition of sand grains along these shorelines. Utilization of these technological advances has recently become more prevalent in coastal research. The resolution and sensitivity of these methods offer unique insights on coastal environments and their relationship to past climate change. However, discrepancies in the analysis and presentation of the data can result in erroneous interpretations. When utilized correctly on prograded barriers these methods (independently or in various combinations) have produced storm records, constructed sea-level curves, quantified sediment budgets, and deciphered coastal evolution. Therefore, combining the application of GPR, OSL, and Lidar (GOaL) on one prograded barrier has the potential to generate three detailed records of (1) storms, (2) sea level, and (3) sediment supply for that coastline. Obtaining all three for one barrier (a GOaL hat-trick) can provide valuable insights into how these factors influenced past and future barrier evolution. Here we argue that systematically achieving GOaL hat-tricks on some of the 300+ prograded barriers worldwide would allow us to disentangle local patterns of sediment supply from the regional effects of storms or global changes in sea level, providing for a direct comparison to climate proxy records. Fully realizing this aim requires standardization of methods to optimize results. The impetus for this initiative is to establish a framework for consistent data collection and analysis that maximizes the potential of GOaL to contribute to climate change research that can assist coastal communities in mitigating future impacts of global warming.
Progress and pitfalls in radiocarbon dating
Publisher: Springer Science and Business Media LLC
Date: 09-2006
DOI: 10.1038/NATURE05214
New ABOX AMS-14C ages remove dating anomalies at Puritjarra rock shelter
Publisher: Informa UK Limited
Date: 11-2001
Divergent trends in land and ocean temperature in the Southern Ocean over the past 18,000 years
Publisher: Springer Science and Business Media LLC
Date: 08-08-2010
DOI: 10.1038/NGEO931
Synchronisation of palaeoenvironmental records over the last 60,000 years, and an extended INTIMATE 1 event stratigraphy to 48,000 b2k
Publisher: Elsevier BV
Date: 03-2012
Climate change not to blame for late Quaternary megafauna extinctions in Australia
Publisher: Springer Science and Business Media LLC
Date: 29-01-2016
DOI: 10.1038/NCOMMS10511
Abstract: Late Quaternary megafauna extinctions impoverished mammalian ersity worldwide. The causes of these extinctions in Australia are most controversial but essential to resolve, because this continent-wide event presaged similar losses that occurred thousands of years later on other continents. Here we apply a rigorous metadata analysis and new ensemble-hindcasting approach to 659 Australian megafauna fossil ages. When coupled with analysis of several high-resolution climate records, we show that megafaunal extinctions were broadly synchronous among genera and independent of climate aridity and variability in Australia over the last 120,000 years. Our results reject climate change as the primary driver of megafauna extinctions in the world’s most controversial context, and instead estimate that the megafauna disappeared Australia-wide ∼13,500 years after human arrival, with shorter periods of coexistence in some regions. This is the first comprehensive approach to incorporate uncertainty in fossil ages, extinction timing and climatology, to quantify mechanisms of prehistorical extinctions.
Genetic and climatic factors in the dispersal of Anatomically Modern Humans Out of Africa
Publisher: Research Square Platform LLC
Date: 24-08-2021
DOI: 10.21203/RS.3.RS-800178/V1
Abstract: The evolutionarily recent dispersal of Anatomically Modern Humans (AMH) out of Africa and across Eurasia provides an opportunity to study rapid genetic adaptation to multiple new environments. Genomic analyses of modern human populations have detected limited signals of strong selection such as hard sweeps, but genetic admixture between populations is capable of obscuring these patterns and is well known in recent human history, such as during the Bronze Age4. Here we show that ancient human genomic datasets contain multiple genetic signatures of strong selection including 57 hard sweeps, many with strong associations with cold adaptation. Similar genetic signatures of adaptation are also observed in adaptively-introgressed archaic hominin loci, as well as modern Arctic human groups. Consistent targets include the regulation of fat storage, skin physiology, cilia function and neural development with multiple associations to modern western diseases. The spatiotemporal patterns of the hard sweeps allow reconstruction of early AMH population dispersals, and reveal a prolonged period of genetic adaptation (~80-50,000 years) following their initial out of Africa movement, before a rapid spread across Eurasia reaching as far as Australia.
Asynchronous climate change between New Zealand and the North Atlantic during the last deglaciation
Publisher: Geological Society of America
Date: 2003
ENSO influence on Holocene Aboriginal populations in Queensland, Australia
Publisher: Elsevier BV
Date: 12-2006
Spatial variation in microbial communities associated with sea-ice algae in Commonwealth Bay, East Antarctica
Publisher: Microbiology Society
Date: 13-04-2022
DOI: 10.1099/MIC.0.001176
Abstract: Antarctic sea-ice forms a complex and dynamic system that drives many ecological processes in the Southern Ocean. Sea-ice microalgae and their associated microbial communities are understood to influence nutrient flow and allocation in marine polar environments. Sea-ice microalgae and their microbiota can have high seasonal and regional ( km 2 ) compositional and abundance variation, driven by factors modulating their growth, symbiotic interactions and function. In contrast, our knowledge of small-scale variation in these communities is limited. Understanding variation across multiple scales and its potential drivers is critical for informing on how multiple stressors impact sea-ice communities and the functions they provide. Here, we characterized bacterial communities associated with sea-ice microalgae and the potential drivers that influence their variation across a range of spatial scales (metres to kms) in a previously understudied area in Commonwealth Bay, East Antarctica where anomalous events have substantially and rapidly expanded local sea-ice coverage. We found a higher abundance and different composition of bacterial communities living in sea-ice microalgae closer to the shore compared to those further from the coast. Variation in community structure increased linearly with distance between s les. Ice thickness and depth to the seabed were found to be poor predictors of these communities. Further research on the small-scale environmental drivers influencing these communities is needed to fully understand how large-scale regional events can affect local function and ecosystem processes.
Early Last Interglacial ocean warming drove substantial ice mass loss from Antarctica
Publisher: Proceedings of the National Academy of Sciences
Date: 11-02-2020
Abstract: The future response of the Antarctic ice sheet to rising temperatures remains highly uncertain. A useful period for assessing the sensitivity of Antarctica to warming is the Last Interglacial (LIG) (129 to 116 ky), which experienced warmer polar temperatures and higher global mean sea level (GMSL) (+6 to 9 m) relative to present day. LIG sea level cannot be fully explained by Greenland Ice Sheet melt (∼2 m), ocean thermal expansion, and melting mountain glaciers (∼1 m), suggesting substantial Antarctic mass loss was initiated by warming of Southern Ocean waters, resulting from a weakening Atlantic meridional overturning circulation in response to North Atlantic surface freshening. Here, we report a blue-ice record of ice sheet and environmental change from the Weddell Sea Embayment at the periphery of the marine-based West Antarctic Ice Sheet (WAIS), which is underlain by major methane hydrate reserves. Constrained by a widespread volcanic horizon and supported by ancient microbial DNA analyses, we provide evidence for substantial mass loss across the Weddell Sea Embayment during the LIG, most likely driven by ocean warming and associated with destabilization of subglacial hydrates. Ice sheet modeling supports this interpretation and suggests that millennial-scale warming of the Southern Ocean could have triggered a multimeter rise in global sea levels. Our data indicate that Antarctica is highly vulnerable to projected increases in ocean temperatures and may drive ice–climate feedbacks that further lify warming.
Rapid global ocean-atmosphere response to Southern Ocean freshening during the last glacial
Publisher: Springer Science and Business Media LLC
Date: 12-09-2017
DOI: 10.1038/S41467-017-00577-6
Abstract: Contrasting Greenland and Antarctic temperatures during the last glacial period (115,000 to 11,650 years ago) are thought to have been driven by imbalances in the rates of formation of North Atlantic and Antarctic Deep Water (the ‘bipolar seesaw’). Here we exploit a bidecadally resolved 14 C data set obtained from New Zealand kauri ( Agathis australis ) to undertake high-precision alignment of key climate data sets spanning iceberg-rafted debris event Heinrich 3 and Greenland Interstadial (GI) 5.1 in the North Atlantic (~30,400 to 28,400 years ago). We observe no ergence between the kauri and Atlantic marine sediment 14 C data sets, implying limited changes in deep water formation. However, a Southern Ocean (Atlantic-sector) iceberg rafted debris event appears to have occurred synchronously with GI-5.1 warming and decreased precipitation over the western equatorial Pacific and Atlantic. An ensemble of transient meltwater simulations shows that Antarctic-sourced salinity anomalies can generate climate changes that are propagated globally via an atmospheric Rossby wave train.
The ‘human revolution’ in lowland tropical Southeast Asia: the antiquity and behavior of anatomically modern humans at Niah Cave (Sarawak, Borneo)
Publisher: Elsevier BV
Date: 03-2007
DOI: 10.1016/J.JHEVOL.2006.08.011
Abstract: Recent research in Europe, Africa, and Southeast Asia suggests that we can no longer assume a direct and exclusive link between anatomically modern humans and behavioral modernity (the 'human revolution'), and assume that the presence of either one implies the presence of the other: discussions of the emergence of cultural complexity have to proceed with greater scrutiny of the evidence on a site-by-site basis to establish secure associations between the archaeology present there and the hominins who created it. This paper presents one such case study: Niah Cave in Sarawak on the island of Borneo, famous for the discovery in 1958 in the West Mouth of the Great Cave of a modern human skull, the 'Deep Skull,' controversially associated with radiocarbon dates of ca. 40,000 years before the present. A new chronostratigraphy has been developed through a re-investigation of the lithostratigraphy left by the earlier excavations, AMS-dating using three different comparative pre-treatments including ABOX of charcoal, and U-series using the Diffusion-Absorption model applied to fragments of bones from the Deep Skull itself. Stratigraphic reasons for earlier uncertainties about the antiquity of the skull are examined, and it is shown not to be an 'intrusive' artifact. It was probably excavated from fluvial-pond-desiccation deposits that accumulated episodically in a shallow basin immediately behind the cave entrance lip, in a climate that ranged from times of comparative aridity with complete desiccation, to episodes of greater surface wetness, changes attributed to regional climatic fluctuations. Vegetation outside the cave varied significantly over time, including wet lowland forest, montane forest, savannah, and grassland. The new dates and the lithostratigraphy relate the Deep Skull to evidence of episodes of human activity that range in date from ca. 46,000 to ca. 34,000 years ago. Initial investigations of sediment scorching, pollen, palynomorphs, phytoliths, plant macrofossils, and starch grains recovered from existing exposures, and of vertebrates from the current and the earlier excavations, suggest that human foraging during these times was marked by habitat-tailored hunting technologies, the collection and processing of toxic plants for consumption, and, perhaps, the use of fire at some forest-edges. The Niah evidence demonstrates the sophisticated nature of the subsistence behavior developed by modern humans to exploit the tropical environments that they encountered in Southeast Asia, including rainforest.
Review: Europe's lost world: the rediscovery of Doggerland
Publisher: Cambridge University Press (CUP)
Date: 09-2010
A 250 year periodicity in Southern Hemisphere westerly winds over the last 2600 years
Publisher: Copernicus GmbH
Date: 03-06-2015
Abstract: Abstract. Southern Hemisphere westerly airflow has a significant influence on the ocean–atmosphere system of the mid- to high-latitudes with potentially global climate implications. Unfortunately historic observations only extend back to the late nineteenth century, limiting our understanding of multi-decadal to centennial change. Here we present a highly resolved (30 yr) record of past westerly air strength from a Falkland Islands peat sequence spanning the last 2600 years. Situated under the core latitude of Southern Hemisphere westerly airflow, we identify highly variable changes in exotic pollen derived from South America which can be used to inform on past westerly air strength and location. The results indicate enhanced airflow over the Falklands between 2000 and 1000 cal. yr BP, and associated with increased burning, most probably as a result of higher temperatures and/or reduced precipitation, comparable to records in South America. Spectral analysis of the charcoal record identifies a 250 year periodicity within the data, suggesting solar variability has a modulating influence on Southern Hemisphere westerly airflow with potentially important implications for understanding global climate change through the late Holocene.
Connecting the Greenland ice-core and U∕Th timescales via cosmogenic radionuclides: testing the synchroneity of Dansgaard–Oeschger events
Publisher: Copernicus GmbH
Date: 20-11-2018
Abstract: Abstract. During the last glacial period Northern Hemisphere climate was characterized by extreme and abrupt climate changes, so-called Dansgaard–Oeschger (DO) events. Most clearly observed as temperature changes in Greenland ice-core records, their climatic imprint was geographically widespread. However, the temporal relation between DO events in Greenland and other regions is uncertain due to the chronological uncertainties of each archive, limiting our ability to test hypotheses of synchronous change. In contrast, the assumption of direct synchrony of climate changes forms the basis of many timescales. Here, we use cosmogenic radionuclides (10Be, 36Cl, 14C) to link Greenland ice-core records to U∕Th-dated speleothems, quantify offsets between the two timescales, and improve their absolute dating back to 45 000 years ago. This approach allows us to test the assumption that DO events occurred synchronously between Greenland ice-core and tropical speleothem records with unprecedented precision. We find that the onset of DO events occurs within synchronization uncertainties in all investigated records. Importantly, we demonstrate that local discrepancies remain in the temporal development of rapid climate change for specific events and speleothems. These may either be related to the location of proxy records relative to the shifting atmospheric fronts or to underestimated U∕Th dating uncertainties. Our study thus highlights the potential for misleading interpretations of the Earth system when applying the common practice of climate wiggle matching.
Environmental change and the arrival of people in the Australian region
Publisher: Liverpool University Press
Date: 2006
IPCC and palaeoclimate - An evolving story?
Publisher: Wiley
Date: 04-12-2010
DOI: 10.1002/JQS.1336
The bigger picture: Towards integrating palaeoclimate and environmental data with a history of societal change
Publisher: Wiley
Date: 2010
DOI: 10.1002/JQS.1337
Late Pleistocene and early Holocene change in the Weddell Sea: A new climate record from the Patriot Hills, Ellsworth Mountains, West Antarctica
Publisher: Wiley
Date: 10-2013
DOI: 10.1002/JQS.2668
Sensitivity of the Southern Ocean to enhanced regional Antarctic ice sheet meltwater input
Publisher: American Geophysical Union (AGU)
Date: 10-2015
DOI: 10.1002/2015EF000306
Radiocarbon dating of organic- and carbonate-carbon in Genyornis and Dromaius eggshell using stepped combustion and stepped acidification
Publisher: Elsevier BV
Date: 07-2003
Decadal-scale onset and termination of Antarctic ice-mass loss during the last deglaciation
Publisher: Springer Science and Business Media LLC
Date: 18-11-2021
DOI: 10.1038/S41467-021-27053-6
Abstract: Emerging ice-sheet modeling suggests once initiated, retreat of the Antarctic Ice Sheet (AIS) can continue for centuries. Unfortunately, the short observational record cannot resolve the tipping points, rate of change, and timescale of responses. Iceberg-rafted debris data from Iceberg Alley identify eight retreat phases after the Last Glacial Maximum that each destabilized the AIS within a decade, contributing to global sea-level rise for centuries to a millennium, which subsequently re-stabilized equally rapidly. This dynamic response of the AIS is supported by (i) a West Antarctic blue ice record of ice-elevation drawdown m during three such retreat events related to globally recognized deglacial meltwater pulses, (ii) step-wise retreat up to 400 km across the Ross Sea shelf, (iii) independent ice sheet modeling, and (iv) tipping point analysis. Our findings are consistent with a growing body of evidence suggesting the recent acceleration of AIS mass loss may mark the beginning of a prolonged period of ice sheet retreat and substantial global sea level rise.
Identification and significance of a visible, basalt-rich Vedde Ash layer in a Late-glacial sequence on the Isle of Skye, Inner Hebrides, Scotland
Publisher: Wiley
Date: 2001
DOI: 10.1002/JQS.611
A New Daily Observational Record from Grytviken, South Georgia: Exploring Twentieth-Century Extremes in the South Atlantic
Publisher: American Meteorological Society
Date: 03-2018
Abstract: The sparse nature of observational records across the mid- to high latitudes of the Southern Hemisphere limits the ability to place late-twentieth-century environmental changes in the context of long-term (multidecadal and centennial) variability. Historical records from subantarctic islands offer considerable potential for developing highly resolved records of change. In 1905, a whaling and meteorological station was established at Grytviken on subantarctic South Georgia in the South Atlantic (54°S, 36°W), providing near-continuous daily observations through to present day. This paper reports a new, daily observational record of temperature and precipitation from Grytviken, which is compared to regional datasets and historical reanalysis. The authors find a shift toward increasingly warmer daytime extremes commencing from the mid-twentieth century and accompanied by warmer nighttime temperatures, with an average rate of temperature rise of 0.13°C decade −1 over the period 1907–2016 ( p 0.0001). Analysis of these data and reanalysis products suggest a change of pervasive synoptic conditions across the mid- to high latitudes since the mid-twentieth century, characterized by stronger westerly airflow and associated warm föhn winds across South Georgia. This rapid rate of warming and associated declining habitat suitability has important negative implications for bio ersity, including the survival of key marine biota in the region.
Extraction of rhyolitic component of Vedde microtephra from minerogenic lake sediments
Publisher: Springer Science and Business Media LLC
Date: 1998
Changes in El Niño – Southern Oscillation (ENSO) conditions during the Greenland Stadial 1 (GS-1) chronozone revealed by New Zealand tree-rings
Publisher: Elsevier BV
Date: 12-2016
In one year and out the other
Publisher: Elsevier BV
Date: 12-2006
Reconstructing atmospheric circulation over southern New Zealand: Establishment of modern westerly airflow 5500 years ago and implications for Southern Hemisphere Holocene climate change
Publisher: Elsevier BV
Date: 03-2017
The scientific value and potential of New Zealand swamp kauri
Publisher: Elsevier BV
Date: 03-2018
Using dung fungi to interpret decline and extinction ofmegaherbivores: Problems and solutions
Publisher: Elsevier BV
Date: 02-2015
Correspondence: The Taupo eruption occurred in 232 ± 10 CE, and not later
Publisher: California Digital Library (CDL)
Date: 06-01-2019
The paleoclimate context and future trajectory of extreme summer hydroclimate in eastern Australia
Publisher: American Geophysical Union (AGU)
Date: 12-11-2016
DOI: 10.1002/2016JD024892
The chronology of palaeoenvironmental changes during the Last Glacial-Holocene transition: Towards an event stratigraphy for the British Isles
Publisher: Geological Society of London
Date: 03-1999
Frontier Lapita interaction with resident Papuan populations set the stage for initial peopling of the Pacific
Publisher: Springer Science and Business Media LLC
Date: 21-04-2022
DOI: 10.1038/S41559-022-01735-W
Abstract: The initial peopling of the remote Pacific islands was one of the greatest migrations in human history, beginning three millennia ago by Lapita cultural groups. The spread of Lapita out of an ancestral Asian homeland is a dominant narrative in the origins of Pacific peoples, and although Island New Guinea has long been recognized as a springboard for the peopling of Oceania, the role of Indigenous populations in this remarkable phase of exploration remains largely untested. Here, we report the earliest evidence for Lapita-introduced animals, turtle bone technology and repeated obsidian import in southern New Guinea 3,480-3,060 years ago, synchronous with the establishment of the earliest known Lapita settlements 700 km away. Our findings precede sustained Lapita migrations and pottery introductions by several centuries, occur alongside Indigenous technologies and suggest continued multicultural influences on population ersity despite language replacement. Our work shows that initial Lapita expansion throughout Island New Guinea was more expansive than previously considered, with Indigenous contact influencing migration pathways and island-hopping strategies that culminated in rapid and purposeful Pacific-wide settlement. Later Lapita dispersals through New Guinea were facilitated by earlier contact with Indigenous populations and profoundly influenced the region as a global centre of cultural and linguistic ersity.
Response to Comment on “A global environmental crisis 42,000 years ago”
Publisher: American Association for the Advancement of Science (AAAS)
Date: 19-11-2021
Abstract: Our study on the exact timing and the potential climatic, environmental, and evolutionary consequences of the Lasch s Geomagnetic Excursion has generated the hypothesis that geomagnetism represents an unrecognized driver in environmental and evolutionary change. It is important for this hypothesis to be tested with new data, and encouragingly, none of the studies presented by Picin et al . undermine our model.
Do Southern Hemisphere tree rings record past volcanic events?
Publisher: Copernicus GmbH
Date: 17-12-2021
DOI: 10.5194/CP-2021-171
Abstract: Abstract. Much of our knowledge about the impacts of volcanic events on climate comes from proxy records. However, little is known about the impact of volcanoes on trees from the Southern Hemisphere. We investigated whether volcanic signals could be identified in ring widths from eight New Zealand dendrochronological species, using superposed epoch analysis. We found that most species are good recorders of volcanic dimming and that the magnitude and persistence of the post-event response can be broadly linked to plant life history traits. Across species, site-based factors, particularly altitude and exposure to prevailing conditions, are more important determinants of the strength of the volcanic response than the species. We then investigated whether proxy selection impacts the magnitude of post-volcanic cooling in tree-ring based temperature reconstructions by developing two new multispecies reconstructions of New Zealand summer (December–February) temperature. Both reconstructions showed temperature anomalies remarkably consistent with studies based on instrumental temperature, and with the ensemble mean response of climate models, demonstrating that New Zealand ring widths are reliable indicators of regional volcanic climate response. However, we also found that volcanic response is complex, with positive, negative, and neutral responses identified – sometimes within the same species group. Species-wide composites thus tend to underestimate the volcanic response. The has important implications for the development of future tree ring and multiproxy temperature reconstructions from the Southern Hemisphere.
Technical note: Optimizing the utility of combined GPR, OSL, and LiDAR (GOaL) to extract paleoenvironmental records and decipher shoreline evolution
Publisher: Copernicus GmbH
Date: 30-01-2018
DOI: 10.5194/CP-2018-4
Abstract: Abstract. Records of past sea levels, storms, and their impacts on coastline are crucial in forecasting future changes resulting from anthropogenic global warming. Coastal barriers that have prograded over the Holocene preserve within their accreting sands history of storm erosion and changes in sea level. High-resolution geophysics, geochronology, and remote sensing techniques offer an optimal way to extract these records and decipher shoreline evolution: Light Detection and Ranging (LiDAR) images the lateral extent of relict shoreline dune morphology Ground Penetrating Radar (GPR) data records paleo-dune, beach and nearshore stratigraphy Optically Stimulated Luminescence (OSL) dates when sand grains were deposited that form these shorelines. Utilization of these technological advances has recently become more prevalent in coastal research. The resolution and sensitivity of these methods offer unique insights on coastal environments and their relationship to past climate change. However, discrepancies in analysis and presentation of the data can result in erroneous interpretations. When utilized correctly on prograded barriers these methods (independently or in various combinations) have produced storm records, constructed sea-level curves, quantified sediment budgets, and deciphered coastal evolution. Therefore, combining the application of GPR, OSL, and LiDAR (GOaL) on one prograded barrier has the potential to generate detailed records of storms, sea level, and sediment supply for that coastline. Obtaining this GOaL hat-trick can provide valuable insights into how these three factors influenced past and future barrier evolution. Here we argue that systematically achieving GOaL hat-tricks on some of the 300+ prograded barriers worldwide would allow us to disentangle local patterns of sediment supply from regional effects of storms or global changes in sea level, allowing direct comparison to climate proxy records. To fully realize this aim requires standardization of methods to optimize results. The impetus for this initiative is to establish a framework for consistent data analysis that maximizes the potential of GOaL to contribute to climate change research and assist coastal communities in mitigating future impacts of global warming.
Humans rather than climate the primary cause of Pleistocene megafaunal extinction in Australia
Publisher: Springer Science and Business Media LLC
Date: 20-01-2017
DOI: 10.1038/NCOMMS14142
Abstract: Environmental histories that span the last full glacial cycle and are representative of regional change in Australia are scarce, h ering assessment of environmental change preceding and concurrent with human dispersal on the continent ca. 47,000 years ago. Here we present a continuous 150,000-year record offshore south-western Australia and identify the timing of two critical late Pleistocene events: wide-scale ecosystem change and regional megafaunal population collapse. We establish that substantial changes in vegetation and fire regime occurred ∼70,000 years ago under a climate much drier than today. We record high levels of the dung fungus Sporormiella , a proxy for herbivore biomass, from 150,000 to 45,000 years ago, then a marked decline indicating megafaunal population collapse, from 45,000 to 43,100 years ago, placing the extinctions within 4,000 years of human dispersal across Australia. These findings rule out climate change, and implicate humans, as the primary extinction cause.
Shcal13 Southern Hemisphere calibration, 0-50,000 years cal BP
Publisher: Cambridge University Press (CUP)
Date: 2013
DOI: 10.2458/AZU_JS_RC.55.16783
Abstract: The Southern Hemisphere SHCal04 radiocarbon calibration curve has been updated with the addition of new data sets extending measurements to 2145 cal BP and including the ANSTO Younger Dryas Huon pine data set. Outside the range of measured data, the curve is based upon the ern Hemisphere data sets as presented in IntCal13, with an interhemispheric offset averaging 43 ± 23 yr modeled by an autoregressive process to represent the short-term correlations in the offset.
Multidecadal variations in Southern Hemisphere atmospheric 14C: Evidence against a Southern Ocean sink at the end of the Little Ice Age CO2 anomaly
Publisher: American Geophysical Union (AGU)
Date: 02-2016
DOI: 10.1002/2015GB005257
Supplementary material to "A global mean sea-surface temperature dataset for the Last Interglacial (129–116 kyr) and contribution of thermal expansion to sea-level change"
Publisher: Copernicus GmbH
Date: 29-01-2020
Pleistocene glacial history of the New Zealand subantarctic islands
Publisher: Copernicus GmbH
Date: 14-03-2019
Abstract: Abstract. The New Zealand subantarctic islands of Auckland and C bell, situated between the subtropical front and the Antarctic Convergence in the Pacific sector of the Southern Ocean, provide valuable terrestrial records from a globally important climatic region. Whilst the islands show clear evidence of past glaciation, the timing and mechanisms behind Pleistocene environmental and climate changes remain uncertain. Here we present a multidisciplinary study of the islands – including marine and terrestrial geomorphological surveys, extensive analyses of sedimentary sequences, a comprehensive dating programme, and glacier flow line modelling – to investigate multiple phases of glaciation across the islands. We find evidence that the Auckland Islands hosted a small ice cap 384 000 ± 26 000 years ago (384±26 ka), most likely during Marine Isotope Stage 10, a period when the subtropical front was reportedly north of its present-day latitude by several degrees, and consistent with hemispheric-wide glacial expansion. Flow line modelling constrained by field evidence suggests a more restricted glacial period prior to the LGM that formed substantial valley glaciers on the C bell and Auckland Islands around 72–62 ka. Despite previous interpretations that suggest the maximum glacial extent occurred in the form of valley glaciation at the Last Glacial Maximum (LGM ∼21 ka), our combined approach suggests minimal LGM glaciation across the New Zealand subantarctic islands and that no glaciers were present during the Antarctic Cold Reversal (ACR ∼15–13 ka). Instead, modelling implies that despite a regional mean annual air temperature depression of ∼5 ∘C during the LGM, a combination of high seasonality and low precipitation left the islands incapable of sustaining significant glaciation. We suggest that northwards expansion of winter sea ice during the LGM and subsequent ACR led to precipitation starvation across the middle to high latitudes of the Southern Ocean, resulting in restricted glaciation of the subantarctic islands.
Urgent need for an integrated policy framework for biodiversity loss and climate change
Publisher: Springer Science and Business Media LLC
Date: 17-06-2020
Supplementary material to "Brief communication: Changing mid-twentieth century Antarctic sea ice variability linked to tropical forcing"
Publisher: Copernicus GmbH
Date: 25-04-2017
This was no antarctic pleasure cruise
Publisher: Springer Science and Business Media LLC
Date: 2014
DOI: 10.1038/505133A
Early Last Interglacial ocean warming drove substantial ice mass loss from Antarctica
Publisher: Copernicus GmbH
Date: 23-03-2020
DOI: 10.5194/EGUSPHERE-EGU2020-12771
Abstract: & & & strong& The future response of the Antarctic ice sheet to rising temperatures remains highly uncertain. A useful period for assessing the sensitivity of Antarctica to warming is the Last Interglacial (LIG 129-116 kyr), which experienced warmer polar temperatures and higher global mean sea level (GMSL +6 to 9 m) relative to present day. LIG sea level cannot be fully explained by Greenland Ice Sheet melt (~2 m), ocean thermal expansion and melting mountain glaciers (~1 m), suggesting substantial Antarctic mass loss was initiated by warming of Southern Ocean waters, resulting from a weakening Atlantic Meridional Overturning Circulation in response to North Atlantic surface freshening. & Here we report a blue-ice record of ice-sheet and environmental change from the Weddell Sea Embayment at the periphery of the marine-based West Antarctic Ice Sheet (WAIS) which is underlain by major methane hydrate reserves. Constrained by a widespread volcanic horizon and supported by ancient microbial DNA analyses, we provide the first evidence for substantial mass loss across the Weddell Sea Embayment during the Last Interglacial, most likely driven by ocean warming and associated with destabilization of sub-glacial hydrates. Ice-sheet modelling supports this interpretation and suggests that millennial-scale warming of the Southern Ocean could have triggered a multi-meter rise in global sea levels. Our data indicate that Antarctica is highly vulnerable to projected increases in ocean temperatures and may drive ice-climate feedbacks that further lify warming.& /strong& & &
Supplementary material to "Pleistocene glacial history of the New Zealand subantarctic islands"
Publisher: Copernicus GmbH
Date: 25-05-2018
Chironomid-inferred late-glacial summer air temperatures from Lough Nadourcan, Co. Donegal, Ireland
Publisher: Wiley
Date: 19-05-2010
DOI: 10.1002/JQS.1399
Lateglacial and early Holocene palaeoenvironmental 'events' in Sluggan Bog, Northern Ireland: Comparisons with the Greenland NGRIP GICC05 event stratigraphy
Publisher: Elsevier BV
Date: 03-2012
Radiocarbon dating of old charcoal using a wet oxidation, stepped-combustion procedure
Publisher: University of Arizona Libraries
Date: 1999
Geochemical changes recorded in Lynch's Crater, Northeastern Australia, over the past 50 ka
Publisher: Elsevier BV
Date: 04-2006
Extending the observational record to provide new insights into invasive alien species in a coastal dune environment of New Zealand
Publisher: Elsevier BV
Date: 09-2018
Impacts of a changing climate on a century of extreme flood regime of northwest Australia
Publisher: Copernicus GmbH
Date: 24-10-2014
DOI: 10.5194/HESSD-11-11905-2014
Abstract: Abstract. Globally, there has been much recent effort to improve understanding of climate change-related shifts in rainfall patterns, variability and extremes. Comparatively little work have focused on how such shifts might be altering hydrological regimes within arid regional basins, where impacts are expected to be most significant. Here, we sought to identify the main hydroclimatic determinants of the strongly episodic flood regime of a large catchment in the semi-arid, subtropical northwest of Australia and to establish the background of hydrologic variability for the region over the last century. We used a monthly sequence of satellite images to quantify surface water expression on the Fortescue Marsh, the largest water feature of inland northwest Australia, from 1988 to 2012. We used this sequence together with instrumental rainfall data to build a multiple linear model and reconstruct monthly history of floods and droughts since 1912. We found that severe and intense regional rainfall events, as well as the sequence of recharge events both within and between years, determine surface water expression on the floodplain (i.e., total rainfall, number of rain days and carried-over inundated area R2adj = 0.79 p value 0.001, ERMSP = 56 km2). The most severe inundation (~1000 km2) over the last century was recorded in 2000. The Fortescue Marsh was completely dry for 32% of all years, for periods of up to four consecutive years. Extremely wet years (seven of the 100 years) caused the Marsh to remain inundated for up to 12 months only 25% of years (9% of all months) had floods of greater than 300 km2. Duration, severity and frequency of inundations between 1999 and 2006 were above average and unprecedented when compared to the last century. While there is high inter-annual variability in the system, changes to the flooding regime over the last 20 years suggest that the wetland will become more persistent in response to increased frequency and intensity of extreme rainfall events for the region, which in turn will likely impact on the structure and functioning of this highly specialized ecosystem.
The use of magnetic separation techniques to detect basaltic microtephra in last glacial-interglacial transition (LGIT; 15-10 ka cal. BP) sediment sequences in Scotland
Publisher: Geological Society of London
Date: 05-2002
DOI: 10.1144/SJG38010021
Extreme wet conditions coincident with Bronze Age abandonment of upland areas in Britain
Publisher: Elsevier BV
Date: 03-2015
Millennial and orbital variations of El Niño/Southern Oscillation and high-latitude climate in the last glacial period
Publisher: Springer Science and Business Media LLC
Date: 03-2004
DOI: 10.1038/NATURE02386
The implications of the recently recognized mid-20th century shift in the Earth system
Publisher: SAGE Publications
Date: 24-02-2022
Abstract: Satellite observations offering detailed records of global environmental change are only available from 1979. Emerging studies combining high-quality instrumental and natural observations highlight that the Earth system experienced a substantial shift across the mid-20th century, one that appears to have taken place before the Great Acceleration of human activities from the 1950s. These new results have far-reaching implications for understanding ice-ocean-atmospheric interactions in the Anthropocene and highlight the urgent need for drastic cuts in carbon emissions to limit the impact of future warming.
Effects of sea-ice cover on marine benthic communities: a natural experiment in Commonwealth Bay, East Antarctica
Publisher: Springer Science and Business Media LLC
Date: 08-04-2015
Devensian Lateglacial environmental changes in Britain: A multi-proxy environmental record from Llanilid, South Wales, UK
Publisher: Elsevier BV
Date: 03-2003
Impacts of marine instability across the East Antarctic Ice Sheet on Southern Ocean dynamics
Publisher: Copernicus GmbH
Date: 30-09-2016
Abstract: Abstract. Recent observations and modelling studies have demonstrated the potential for rapid and substantial retreat of large sectors of the East Antarctic Ice Sheet (EAIS). This has major implications for ocean circulation and global sea level. Here we examine the effects of increasing meltwater from the Wilkes Basin, one of the major marine-based sectors of the EAIS, on Southern Ocean dynamics. Climate model simulations reveal that the meltwater flux rapidly stratifies surface waters, leading to a dramatic decrease in the rate of Antarctic Bottom Water (AABW) formation. The surface ocean cools but, critically, the Southern Ocean warms by more than 1 °C at depth. This warming is accompanied by a Southern Ocean-wide “domino effect”, whereby the warming signal propagates westward with depth. Our results suggest that melting of one sector of the EAIS could result in accelerated warming across other sectors, including the Weddell Sea sector of the West Antarctic Ice Sheet. Thus, localised melting of the EAIS could potentially destabilise the wider Antarctic Ice Sheet.
Early warnings and missed alarms for abrupt monsoon transitions
Publisher: Copernicus GmbH
Date: 08-12-2015
Abstract: Abstract. Palaeo-records from China demonstrate that the East Asian Summer Monsoon (EASM) is dominated by abrupt and large magnitude monsoon shifts on millennial timescales, switching between periods of high and weak monsoon rains. It has been hypothesized that over these timescales, the EASM exhibits two stable states with bifurcation-type tipping points between them. Here we test this hypothesis by looking for early warning signals of past bifurcations in speleothem δ18O records from Sanbao Cave and Hulu Cave, China, spanning the penultimate glacial cycle. We find that although there are increases in both autocorrelation and variance preceding some of the monsoon transitions during this period, it is only immediately prior to the abrupt monsoon shift at the penultimate deglaciation (Termination II) that statistically significant increases are detected. To supplement our data analysis, we produce and analyse multiple model simulations that we derive from these data. We find hysteresis behaviour in our model simulations with transitions directly forced by solar insolation. However, signals of critical slowing down, which occur on the approach to a bifurcation, are only detectable in the model simulations when the change in system stability is sufficiently slow to be detected by the s ling resolution of the data set. This raises the possibility that the early warning "alarms" were missed in the speleothem data over the period 224–150 kyr and it was only at the monsoon termination that the change in the system stability was sufficiently slow to detect early warning signals.
The potential of New Zealand kauri (Agathis australis) for testing the synchronicity of abrupt climate change during the Last Glacial Interval (60,000–11,700 years ago)
Publisher: Elsevier BV
Date: 12-2010
Palaeovolcanic forcing of short-term dendroisotropic depletion: The effect of decreased solar intensity on Irish oak
Publisher: American Geophysical Union (AGU)
Date: 02-2005
DOI: 10.1029/2004GL021623
Tephrochronology of Last Termination sequences in Europe: A protocol for improved analytical precision and robust correlation procedures (a joint SCOTAV-INTIMATE proposal)
Publisher: Wiley
Date: 02-2004
DOI: 10.1002/JQS.822
Attitudes of healthcare providers towards family involvement and presence in adult critical care units in Saudi Arabia: a quantitative study.
Publisher: Wiley
Date: 20-12-2014
DOI: 10.1111/JOCN.12520
Abstract: To describe healthcare providers' attitudes to family involvement during routine care and family presence during resuscitation or other invasive procedures in adult intensive care units in Saudi Arabia. Previous research has shown that healthcare professionals have revealed a ersity of opinions on family involvement during routine care and family presence during resuscitation or other invasive procedures. Attitude assessment can provide an indication of staff acceptance or rejection of the practice and also help identify key potential barriers that will need to be addressed. It has also been evident that participation in the care has potential benefits for patients and families as well as healthcare providers. A quantitative descriptive design. A questionnaire was used with a convenience s le of 468 healthcare providers who were recruited from eight intensive care units. The analysis found that healthcare providers had positive attitudes towards family involvement during routine care, but negative attitudes towards family presence during resuscitation or other invasive procedures. Physicians expressed more opposition to the practice than did nurses and respiratory therapists. Staff indicated a need to develop written guidelines and policies, as well as educational programmes, to address this sensitive issue in clinical practice. Family is an important resource in patient care in the context of the critical care environment. Clinical barriers including resources, hospital policies and guidelines, staff and public education should be taken into account to facilitate family integration to the care model. The findings can help to develop policies and guidelines for safe implementation of the practice. They can also encourage those who design nursing and other medical curricula to place more emphasis on the role of the family especially in critical care settings.
Climatic variability in the southwest Pacific during the Last Termination (20-10 kyr BP)
Publisher: Elsevier BV
Date: 05-2006
ATMOSPHERIC RADIOCARBON FOR THE PERIOD 1950–2019
Publisher: Cambridge University Press (CUP)
Date: 23-11-2021
DOI: 10.1017/RDC.2021.95
Abstract: This paper presents a compilation of atmospheric radiocarbon for the period 1950–2019, derived from atmospheric CO 2 s ling and tree rings from clean-air sites. Following the approach taken by Hua et al. (2013), our revised and extended compilation consists of zonal, hemispheric and global radiocarbon ( 14 C) data sets, with monthly data sets for 5 zones (Northern Hemisphere zones 1, 2, and 3, and Southern Hemisphere zones 3 and 1–2). Our new compilation includes smooth curves for zonal data sets that are more suitable for dating applications than the previous approach based on simple averaging. Our new radiocarbon dataset is intended to help facilitate the use of atmospheric bomb 14 C in carbon cycle studies and to accommodate increasing demand for accurate dating of recent (post-1950) terrestrial s les.
What caused extinction of the Pleistocene megafauna of Sahul?
Publisher: The Royal Society
Date: 10-02-2016
Abstract: During the Pleistocene, Australia and New Guinea supported a rich assemblage of large vertebrates. Why these animals disappeared has been debated for more than a century and remains controversial. Previous synthetic reviews of this problem have typically focused heavily on particular types of evidence, such as the dating of extinction and human arrival, and have frequently ignored uncertainties and biases that can lead to misinterpretation of this evidence. Here, we review erse evidence bearing on this issue and conclude that, although many knowledge gaps remain, multiple independent lines of evidence point to direct human impact as the most likely cause of extinction.
Carbon isotope fractionation in wood during carbonization
Publisher: Elsevier BV
Date: 02-2006
Sediment mixing at Nonda Rock: Investigations of stratigraphic integrity at an early archaeological site in northern Australia and implications for the human colonisation of the continent
Publisher: Wiley
Date: 06-2007
DOI: 10.1002/JQS.1136
Quaternary climatic, environmental and archaeological change in Australasia
Publisher: Wiley
Date: 2007
DOI: 10.1002/JQS.1139
Using the paleorecord to evaluate climate and fire interactions in Australia
Publisher: Annual Reviews
Date: 05-2007
DOI: 10.1146/ANNUREV.EARTH.35.092006.145055
Abstract: Burning has been a near-continuous feature of the Australian environment but has become progressively more important since the mid-Tertiary, associated with the development of the characteristic sclerophyll vegetation. In the Quaternary, the extent of burning has varied temporally and regionally with glacial-interglacial cyclicity. Burning during glacial periods was reduced in drier areas, presumably because of a critical reduction in fuel availability, but increased in relatively wetter areas where fuel levels were high. On both glacial and Holocene timescales, peaks in charcoal often accompany transitions between fire-insensitive vegetation types, suggesting that burning is facilitated during periods of climate change and environmental instability. This suggestion has been supported by the demonstration of close relationships between fire and El Niño activity. Burning has also increased progressively over the past few hundred thousand years with major accelerations around the time of first human settlement of the continent and with the arrival of Europeans. To provide a firmer base for application of paleofire records to environmental management, there is an urgent need for a spatially more-substantial coverage of high-resolution fire records with good chronological control.
Late-glacial and Holocene vegetation and climatic history of the Cass Basin, central South Island, New Zealand
Publisher: Cambridge University Press (CUP)
Date: 11-2004
DOI: 10.1016/J.YQRES.2004.09.003
Abstract: Lithology, pollen, macrofossils, and stable carbon isotopes from an intermontane basin bog site in southern New Zealand provide a detailed late-glacial and early Holocene vegetation and climate record. Glacial retreat occurred before 17,000 cal yr B.P., and tundra-like grassland"shrubland occupied the basin shortly after. Between 16,500 and 14,600 cal yr B.P., a minor regional expansion of forest patches occurred in response to warming, but the basin remained in shrubland. Forest retreated between 14,600 and 13,600 cal yr B.P., at about the time of the Antarctic Cold Reversal. At 13,600 cal yr B.P., a steady progression from shrubland to tall podocarp forest began as the climate ameliorated. Tall, temperate podocarp trees replaced stress-tolerant shrubs and trees between 12,800 and 11,300 cal yr B.P., indicating sustained warming during the Younger Dryas Chronozone (YDC). Stable isotopes suggest increasing atmospheric humidity from 11,800 to 9300 cal yr B.P. Mild (annual temperatures at least 1°C higher than present), and moist conditions prevailed from 11,000 to 10,350 cal yr B.P. Cooler, more variable conditions followed, and podocarp forest was completely replaced by montane Nothofagus forest at around 7500 cal yr B.P. with the onset of the modern climate regime. The Cass Basin late-glacial climate record closely matches the Antarctic ice core records and is in approximate antiphase with the North Atlantic.
Supplementary material to "Connecting the Greenland ice-core and U / Th timescales via cosmogenic radionuclides: Testing the synchronicity of Dansgaard-Oeschger events"
Publisher: Copernicus GmbH
Date: 13-07-2018
Connecting the Greenland ice-core and U / Th timescales via cosmogenic radionuclides: Testing the synchronicity of Dansgaard-Oeschger events
Publisher: Copernicus GmbH
Date: 13-07-2018
DOI: 10.5194/CP-2018-85
Abstract: Abstract. During the last glacial period Northern Hemisphere climate was characterized by extreme and abrupt climate changes, so-called Dansgaard-Oeschger (DO) events. Most clearly observed as temperature changes in Greenland ice-core records, their climatic imprint was geographically widespread. However, the temporal relation between DO-events in Greenland and other regions is uncertain due to the chronological uncertainties of each archive, limiting our ability to test hypotheses of synchronous change. On the contrary, the assumption of direct synchrony of climate changes forms the basis of many timescales. Here, we use cosmogenic radionuclides (10Be, 36Cl, 14C) to link Greenland ice-core records to U / Th-dated speleothems, quantify offsets between both timescales, and improve their absolute dating back to 45 000 years ago. This approach allows us to test the assumption that DO-events occurred synchronously between Greenland ice-core and tropical speleothem records at unprecedented precision. We find that the onset of DO-events occurs within synchronization uncertainties in all investigated records. Importantly, we demonstrate that there remain local discrepancies in the temporal development of rapid climate change for specific events and speleothems. These may be either related to the location of proxy records relative to the shifting atmospheric fronts or to underestimated U / Th-dating uncertainties. Our study thus highlights the potential for misleading interpretations of the Earth system when applying the common practice of climate wiggle-matching.
Growth rates and ages of some key tree species from subantarctic Auckland and Campbell Islands
Publisher: New Zealand Ecological Society
Date: 11-2022
Widespread Denisovan ancestry in Island Southeast Asia but no evidence of substantial super-archaic hominin admixture
Publisher: Springer Science and Business Media LLC
Date: 22-03-2021
Exploring Pacific Island hydroclimatic extremes using the South Pacific Drought Atlas
Publisher: Copernicus GmbH
Date: 15-05-2023
DOI: 10.5194/EGUSPHERE-EGU23-10570
Abstract: Droughts are a natural occurrence in many small Pacific Islands and can have severe impacts on local populations and environments. The El Ni& #241 o-Southern Oscillation (ENSO) is a well-known driver of drought in the South Pacific, but our understanding of extreme ENSO events and their influence on island hydroclimate is limited by the short instrumental record and the infrequency of ENSO extremes. To address this gap, we present the South Pacific Drought Atlas (SPaDA), a multi-proxy, spatially resolved reconstruction of the November-April Standardised Precipitation Evapotranspiration Index for the southwest Pacific islands. The reconstruction integrates coral proxies, which provide local information on the South Pacific hydroclimate but are limited in number and length, with a network of continental tree-ring chronologies targeting Pacific climate variability through remote teleconnections. The reconstruction demonstrates the benefits of multi-proxy reconstructions incorporating tree rings, which allow for the alignment of other proxy records without chronological error.The SPaDA provides a 350-year, continuous dataset of climate information, which can be used to explore the occurrence of extreme events in the pre-instrumental period. The SPaDA closes the gap between existing paleo-reconstructions of point ENSO indices, and a spatially resolved drought atlas, allowing both the hydroclimate of in idual islands and regional patterns of drought to be assessed. The benefit of a spatially resolved dataset to assess climate extremes in small Pacific islands is highlighted in the case of extreme El Ni& #241 o events, which can have substantially different hydroclimatic impacts than more moderate events.We used an Isolation Forest, an unsupervised machine learning algorithm, to identify anomalous hydroclimatic states in the SPaDA that may indicate the occurrence of an extreme event. Extreme El Ni& #241 o events characterised by very strong southwest Pacific drought anomalies and a zonal South Pacific Convergence Zone orientation are shown to have occurred semi-regularly throughout the reconstruction interval, providing a valuable baseline to compare to climate model projections. By identifying the spatial patterns of drought resulting from extreme events, we can better understand the impacts these events may have on in idual Pacific Islands in the future.
Archaeology and age of a new hominin from Flores in eastern Indonesia
Publisher: Springer Science and Business Media LLC
Date: 10-2004
DOI: 10.1038/NATURE02956
Abstract: Excavations at Liang Bua, a large limestone cave on the island of Flores in eastern Indonesia, have yielded evidence for a population of tiny hominins, sufficiently distinct anatomically to be assigned to a new species, Homo floresiensis. The finds comprise the cranial and some post-cranial remains of one in idual, as well as a premolar from another in idual in older deposits. Here we describe their context, implications and the remaining archaeological uncertainties. Dating by radiocarbon (14C), luminescence, uranium-series and electron spin resonance (ESR) methods indicates that H. floresiensis existed from before 38,000 years ago (kyr) until at least 18 kyr. Associated deposits contain stone artefacts and animal remains, including Komodo dragon and an endemic, dwarfed species of Stegodon. H. floresiensis originated from an early dispersal of Homo erectus (including specimens referred to as Homo ergaster and Homo georgicus) that reached Flores, and then survived on this island refuge until relatively recently. It overlapped significantly in time with Homo sapiens in the region, but we do not know if or how the two species interacted.
Kauri Tree‐Ring Stable Isotopes Reveal a Centennial Climate Downturn Following the Antarctic Cold Reversal in New Zealand
Publisher: American Geophysical Union (AGU)
Date: 24-01-2021
DOI: 10.1029/2020GL090299
Abstract: The dynamics of the Late Glacial have been demonstrated by numerous records from the Northern Hemisphere and far fewer from the Southern Hemisphere (SH). SH paleoclimate records reveal a general warming trend, interrupted by a deglaciation pause Antarctic Cold Reversal (ACR ∼14,700–13,000 cal BP). Here, we present decadal tree‐ring stable isotope chronologies (δ 18 O, δ 13 C) from New Zealand (NZ) subfossil kauri trees ( n = 6) covering the post‐ACR millennium from 13,020 to 11,850 cal BP. We find a distinct, simultaneous downturn (∼12,625–12,375 cal BP) in all tree‐ring proxies paralleling regional tree growth declines, suggesting a widespread climate deterioration. This downturn was characterized by sustained high precipitation, low temperatures, and high relative humidity in NZ with incoming weather fronts from the South Ocean. Despite these promising results, questions remain about what drove the Kauri Downturn and how the hydroclimatic conditions were altered during this time period.
Drivers of abrupt Holocene shifts in West Antarctic ice stream direction determined from combined ice sheet modelling and geologic signatures
Publisher: Cambridge University Press (CUP)
Date: 13-11-2014
DOI: 10.1017/S0954102014000613
Abstract: Determining the millennial-scale behaviour of marine-based sectors of the West Antarctic Ice Sheet (WAIS) is critical to improve predictions of the future contribution of Antarctica to sea level rise. Here high-resolution ice sheet modelling was combined with new terrestrial geological constraints ( in situ 14 C and 10 Be analysis) to reconstruct the evolution of two major ice streams entering the Weddell Sea over 20 000 years. The results demonstrate how marked differences in ice flux at the marine margin of the expanded Antarctic ice sheet led to a major reorganization of ice streams in the Weddell Sea during the last deglaciation, resulting in the eastward migration of the Institute Ice Stream, triggering a significant regional change in ice sheet mass balance during the early to mid Holocene. The findings highlight how spatial variability in ice flow can cause marked changes in the pattern, flux and flow direction of ice streams on millennial timescales in this marine ice sheet setting. Given that this sector of the WAIS is assumed to be sensitive to ocean-forced instability and may be influenced by predicted twenty-first century ocean warming, our ability to model and predict abrupt and extensive ice stream ersions is key to a realistic assessment of future ice sheet sensitivity.
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