ORCID Profile
0000-0003-1246-2344
Current Organisation
Australian National University
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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)
Climate Change Processes | Palaeoclimatology | Physical Geography and Environmental Geoscience | Quaternary Environments | Atmospheric Sciences | Physical Oceanography | Surfacewater Hydrology | Oceanography | Atmospheric sciences | Atmospheric Dynamics | Glaciology | Meteorology | Physical oceanography | Meteorology | Climate change processes | Psychology | Atmospheric dynamics | Environmental Impact Assessment | Sensory Processes, Perception and Performance
ANZSRC Socio-Economic Objective (SEO)
Effects of Climate Change and Variability on Australia (excl. Social Impacts) | Climate Variability (excl. Social Impacts) | Atmospheric Processes and Dynamics | Natural Hazards in Fresh, Ground and Surface Water Environments | Effects of Climate Change and Variability on Antarctic and Sub-Antarctic Environments (excl. Social Impacts) | Climate Change Mitigation Strategies | Climate Change Models | Expanding Knowledge in Psychology and Cognitive Sciences | Natural Hazards in Coastal and Estuarine Environments | Social Impacts of Climate Change and Variability | Expanding Knowledge in the Environmental Sciences | Expanding Knowledge in the Earth Sciences |
Related Links
Publications
Tropical Indo-Pacific hydroclimate response to North Atlantic forcing during the last deglaciation as recorded by a speleothem from Sumatra, Indonesia
Publisher: Elsevier BV
Date: 06-2018
Global climate changes during the most recent two millennia
Publisher: Copernicus GmbH
Date: 23-03-2020
DOI: 10.5194/EGUSPHERE-EGU2020-13378
Abstract: & & The past two thousand years is a key interval for climate science because this period encompasses both the era of human-induced global warming and a much longer interval when changes in Earth's climate were governed principally by natural drivers. This earlier 'pre-industrial' period is particularly important for two reasons. Firstly, we now have a growing number of well-dated, climate sensitive proxy data with high temporal resolution that spans the full period. Secondly, the pre-industrial climate provides context for present-day climate change, sets real-world targets against which to evaluate the performance of climate models, and allows us to address other questions of Earth sciences that cannot be answered using only a century and a half of observational data.& & & & & Here, we first provide several perspectives on the concept of a 'pre-industrial climate'. Then, we highlight the activities of the PAGES 2k Network, an international collaborative effort focused on global climate change during the past two thousand years. We highlight those aspects of pre-industrial conditions (including both past climate changes and past climate drivers) that are not yet well constrained, and suggest potential areas for research during this period that would be relevant to the evolution of Earth's future climate.& &
High-resolution aerosol concentration data from the Greenland NorthGRIP and NEEM deep ice cores
Publisher: Copernicus GmbH
Date: 16-03-2022
DOI: 10.5194/ESSD-14-1215-2022
Abstract: Abstract. Records of chemical impurities from ice cores enable us to reconstruct the past deposition of aerosols onto polar ice sheets and alpine glaciers. Through this they allow us to gain insight into changes of the source, transport and deposition processes that ultimately determine the deposition flux at the coring location. However, the low concentrations of the aerosol species in the ice and the resulting high risk of contamination pose a formidable analytical challenge, especially if long, continuous and highly resolved records are needed. Continuous flow analysis, CFA, the continuous melting, decontamination and analysis of ice-core s les has mostly overcome this issue and has quickly become the de facto standard to obtain high-resolution aerosol records from ice cores after its inception at the University of Bern in the mid-1990s. Here, we present continuous records of calcium (Ca2+), sodium (Na+), ammonium (NH4+), nitrate (NO3-) and electrolytic conductivity at 1 mm depth resolution from the NGRIP (North Greenland Ice Core Project) and NEEM (North Greenland Eemian Ice Drilling) ice cores produced by the Bern Continuous Flow Analysis group in the years 2000 to 2011 (Erhardt et al., 2021). Both of the records were previously used in a number of studies but were never published in full 1 mm resolution. Alongside the 1 mm datasets we provide decadal averages, a detailed description of the methods, relevant references, an assessment of the quality of the data and its usable resolution. Along the way we will also give some historical context on the development of the Bern CFA system. The data is available in full 1 mm and 10-year-averaged resolution on PANGAEA (0.1594/PANGAEA.935838, Erhardt et al., 2021)
Palaeoclimate perspectives on the Indian Ocean Dipole
Publisher: Elsevier BV
Date: 06-2020
Framing and Context of the Report
Publisher: Cambridge University Press
Date: 19-05-2022
Supplementary material to "No role for industrial black carbon in forcing 19th century glacier retreat in the Alps"
Publisher: Copernicus GmbH
Date: 20-02-2018
Recent intensification of tropical climate variability in the Indian Ocean
Publisher: Springer Science and Business Media LLC
Date: 16-11-2008
DOI: 10.1038/NGEO357
Seasonal characteristics of the Indian Ocean Dipole during the Holocene epoch
Publisher: Springer Science and Business Media LLC
Date: 2007
DOI: 10.1038/NATURE05477
Abstract: The Indian Ocean Dipole (IOD)--an oscillatory mode of coupled ocean-atmosphere variability--causes climatic extremes and socio-economic hardship throughout the tropical Indian Ocean region. There is much debate about how the IOD interacts with the El Niño/Southern Oscillation (ENSO) and the Asian monsoon, and recent changes in the historic ENSO-monsoon relationship raise the possibility that the properties of the IOD may also be evolving. Improving our understanding of IOD events and their climatic impacts thus requires the development of records defining IOD activity in different climatic settings, including prehistoric times when ENSO and the Asian monsoon behaved differently from the present day. Here we use coral geochemical records from the equatorial eastern Indian Ocean to reconstruct surface-ocean cooling and drought during in idual IOD events over the past approximately 6,500 years. We find that IOD events during the middle Holocene were characterized by a longer duration of strong surface ocean cooling, together with droughts that peaked later than those expected by El Niño forcing alone. Climate model simulations suggest that this enhanced cooling and drying was the result of strong cross-equatorial winds driven by the strengthened Asian monsoon of the middle Holocene. These IOD-monsoon connections imply that the socioeconomic impacts of projected future changes in Asian monsoon strength may extend throughout Australasia.
Early onset of industrial-era warming across the oceans and continents
Publisher: Springer Science and Business Media LLC
Date: 24-08-2016
DOI: 10.1038/NATURE19082
Abstract: The evolution of industrial-era warming across the continents and oceans provides a context for future climate change and is important for determining climate sensitivity and the processes that control regional warming. Here we use post-ad 1500 palaeoclimate records to show that sustained industrial-era warming of the tropical oceans first developed during the mid-nineteenth century and was nearly synchronous with Northern Hemisphere continental warming. The early onset of sustained, significant warming in palaeoclimate records and model simulations suggests that greenhouse forcing of industrial-era warming commenced as early as the mid-nineteenth century and included an enhanced equatorial ocean response mechanism. The development of Southern Hemisphere warming is delayed in reconstructions, but this apparent delay is not reproduced in climate simulations. Our findings imply that instrumental records are too short to comprehensively assess anthropogenic climate change and that, in some regions, about 180 years of industrial-era warming has already caused surface temperatures to emerge above pre-industrial values, even when taking natural variability into account.
Acceleration of snow melt in an Antarctic Peninsula ice core during the twentieth century
Publisher: Springer Science and Business Media LLC
Date: 14-04-2013
DOI: 10.1038/NGEO1787
Reconstructions of the southern annular mode (SAM) during the last millennium
Publisher: SAGE Publications
Date: 22-11-2017
Abstract: The leading mode of atmospheric variability in the Southern Hemisphere is the Southern Annular Mode (SAM), which affects the atmosphere and ocean from the mid-latitudes to the Antarctic. However, the short instrumental record of the SAM does not adequately represent its multi-decadal to centennial-scale variability. Long palaeoclimatic reconstructions of the SAM would improve our understanding of its low frequency behavior and its effects on regional temperature, rainfall, sea ice, and ecosystem processes. In this progress report, we review three published palaeoclimatic reconstructions available for understanding multi-decadal to centennial-scale variability of the SAM. Reconstructions reviewed here show similar patterns of decadal SAM variability during the last two centuries, but earlier centuries are less coherent. Reconstructions clearly maintain similar trends towards more positive SAM states since the onset of significant anthropogenic climate forcing from rising greenhouse gas (GHG) concentrations and ozone depletion and these excursions appear unprecedented over at least the last 500 years. We describe how new multi-proxy reconstructions of the SAM could further improve our understanding of its long-term variability and effects across all geographic sectors of the Southern Hemisphere. Here, we recommend careful selection and development of proxies in SAM-sensitive regions and seasons. In particular, proxies related to cool-season conditions and from the poorly-s led Indian Ocean sector would allow for a true circumpolar and year-round reconstruction of past SAM variability.
Higher frequency of Central Pacific El Niño events in recent decades relative to past centuries
Publisher: Springer Science and Business Media LLC
Date: 06-05-2019
Evolution of the Southern Annular Mode during the past millennium
Publisher: Springer Science and Business Media LLC
Date: 11-05-2014
DOI: 10.1038/NCLIMATE2235
Palaeoclimate constraints on the impact of 2 °C anthropogenic warming and beyond
Publisher: Springer Science and Business Media LLC
Date: 25-06-2018
No role for industrial black carbon in forcing 19th century glacier retreat in the Alps
Publisher: Copernicus GmbH
Date: 20-02-2018
DOI: 10.5194/TC-2018-22
Abstract: Abstract. Light absorbing aerosols in the atmosphere and cryosphere play an important role in the climate system. Their presence in ambient air and snow changes radiative properties of these media, thus contributing to increased atmospheric warming and snowmelt. High spatio-temporal variability of aerosol concentrations and a shortage of long-term observations contribute to large uncertainties in properly assigning the climate effects of aerosols through time. Starting around 1860 AD, many glaciers in the European Alps began to retreat from their maximum mid-19th century terminus positions, thereby visualizing the end of the Little Ice Age in Europe. Radiative forcing by increasing deposition of industrial black carbon to snow has been suggested as the main driver of the abrupt glacier retreats in the Alps. Basis for this hypothesis were model simulations using elemental carbon concentrations at low temporal resolution from two ice cores in the Alps. Here we present sub-annually resolved, well-replicated concentration records of refractory black carbon (rBC using soot photometry) as well as distinctive tracers for mineral dust, biomass burning and industrial pollution from the Colle Gnifetti ice core in the Alps from 1741–2015 AD. These records allow precise assessment of a potential relation between the timing of observed acceleration of glacier melt in the mid-19th century with an increase of rBC deposition on the glacier caused by the industrialization of Western Europe. Our study reveals that in 1875 AD, the time when European rBC emission rates started to significantly increase, the majority of Alpine glaciers had already experienced more than 80 % of their total 19th century length reduction. Industrial BC emissions can, therefore, not been considered as the primary forcing for the rapid deglaciation at the end of the Little Ice Age in the Alps. BC records from the Alps and Greenland also reveal the limitations of bottom-up emission inventories to represent a realistic evolution of anthropogenic BC emissions since preindustrial times.
The Iso2k Database: A global compilation of paleo-δ<sup>18</sup>O and δ<sup>2</sup>H records to aid understanding of Common Era climate
Publisher: Copernicus GmbH
Date: 05-02-2020
DOI: 10.5194/ESSD-2020-5
Abstract: Abstract. Reconstructions of global hydroclimate during the Common Era (CE the past ~ 2000 years) are important for providing context for current and future global environmental change. Stable isotope ratios in water are quantitative indicators of hydroclimate on regional to global scales, and these signals are encoded in a wide range of natural geologic archives. Here we present the Iso2k database, a global compilation of previously published datasets from a variety of natural archives that record the stable oxygen (δ18O) or hydrogen (δ2H) isotopic composition of environmental waters, which reflect hydroclimate changes over the CE. The Iso2k database contains 756 isotope records from the terrestrial and marine realms, including: glacier and ground ice (205) speleothems (68) corals, sclerosponges, and mollusks (145) wood (81) lake sediments and other terrestrial sediments (e.g., loess) (158) and marine sediments (99). In idual datasets have temporal resolutions ranging from sub-annual to centennial, and include chronological data where available. A fundamental feature of the database is its comprehensive metadata, which will assist both experts and non-experts in the interpretation of each record and in data synthesis. Key metadata fields have standardized vocabularies to facilitate comparisons across erse archives and with climate model simulated fields. This is the first global-scale collection of water isotope proxy records from multiple types of geological and biological archives. It is suitable for evaluating hydroclimate processes through time and space using large-scale synthesis, model-data intercomparison and (paleo)data assimilation. The Iso2k database is available for download at: 0.6084/m9.figshare.11553162 (McKay and Konecky, 2020).
Response of the East Antarctic Ice Sheet to past and future climate change
Publisher: Springer Science and Business Media LLC
Date: 10-08-2022
DOI: 10.1038/S41586-022-04946-0
Abstract: The East Antarctic Ice Sheet contains the vast majority of Earth's glacier ice (about 52 metres sea-level equivalent), but is often viewed as less vulnerable to global warming than the West Antarctic or Greenland ice sheets. However, some regions of the East Antarctic Ice Sheet have lost mass over recent decades, prompting the need to re-evaluate its sensitivity to climate change. Here we review the response of the East Antarctic Ice Sheet to past warm periods, synthesize current observations of change and evaluate future projections. Some marine-based catchments that underwent notable mass loss during past warm periods are losing mass at present but most projections indicate increased accumulation across the East Antarctic Ice Sheet over the twenty-first century, keeping the ice sheet broadly in balance. Beyond 2100, high-emissions scenarios generate increased ice discharge and potentially several metres of sea-level rise within just a few centuries, but substantial mass loss could be averted if the Paris Agreement to limit warming below 2 degrees Celsius is satisfied.
Oscillations in the southern extent of the Indo-Pacific Warm Pool during the mid-Holocene
Publisher: Elsevier BV
Date: 12-2009
Coral reef death during the 1997 Indian Ocean Dipole linked to Indonesian wildfires
Publisher: American Association for the Advancement of Science (AAAS)
Date: 15-08-2003
Abstract: Geochemical anomalies and growth discontinuities in Porites corals from western Sumatra, Indonesia, record unanticipated reef mortality during anomalous Indian Ocean Dipole upwelling and a giant red tide in 1997. Sea surface temperature reconstructions show that although some past upwelling events have been stronger, there were no analogous episodes of coral mortality during the past 7000 years, indicating that the 1997 red tide was highly unusual. We show that iron fertilization by the 1997 Indonesian wildfires was sufficient to produce the extraordinary red tide, leading to reef death by asphyxiation. These findings highlight tropical wildfires as an escalating threat to coastal marine ecosystems.
Supplementary material to Emerging anthropogenic influence on Australian multi-year droughts with potential for historically unprecedented megadroughts
Publisher: Copernicus GmbH
Date: 04-07-2023
Emerging anthropogenic influence on Australian multi-year droughts with potential for historically unprecedented megadroughts
Publisher: Copernicus GmbH
Date: 04-07-2023
DOI: 10.5194/EGUSPHERE-2023-1398
Abstract: Abstract. In drought-prone Australia, multi-year droughts have detrimental impacts on both the natural environment and human societies. For responsible water management, we need a thorough understanding of the full range of variability in multi-year droughts and how this might change in a warming world. But research into the long-term frequency, persistence, and severity of Australian droughts is limited. This is partly due to the length of the observational record, which is short relative to the time scales of hydroclimatic variability, and hence may not capture the range of possible variability. Using simulations of Australian precipitation over the last millennium (850–2000 CE), we characterise the nature of multi-year meteorological droughts across Australia, and including a particular focus on the Murray-Darling Basin (MDB) the largest agricultural region in Australia. We find that simulated Australian droughts in the twentieth century (1900–2000) are within the bounds of pre-industrial natural variability in terms of drought intensity, severity, and frequency. A tendency to longer droughts in southwestern and eastern Australia (including the MDB) in the 20th century compared with the pre-industrial period suggests an emerging anthropogenic influence, consistent with projected rainfall changes in these regions. Large volcanic eruptions tend to promote drought-free intervals in the MDB. Model simulations suggest future droughts across Australia could be much longer than what has been experienced in the twentieth century, even without any human influence. With the addition of anthropogenic climate change—which favours drought conditions across much of southern Australia, due to reduced cool season rainfall—it is likely that future droughts in Australia will exceed historical experience.
Tropical sea surface temperatures for the past four centuries reconstructed from coral archives
Publisher: American Geophysical Union (AGU)
Date: 03-2015
DOI: 10.1002/2014PA002717
Recent Antarctic Peninsula warming relative to Holocene climate and ice-shelf history
Publisher: Springer Science and Business Media LLC
Date: 22-08-2012
DOI: 10.1038/NATURE11391
Abstract: Rapid warming over the past 50 years on the Antarctic Peninsula is associated with the collapse of a number of ice shelves and accelerating glacier mass loss. In contrast, warming has been comparatively modest over West Antarctica and significant changes have not been observed over most of East Antarctica, suggesting that the ice-core palaeoclimate records available from these areas may not be representative of the climate history of the Antarctic Peninsula. Here we show that the Antarctic Peninsula experienced an early-Holocene warm period followed by stable temperatures, from about 9,200 to 2,500 years ago, that were similar to modern-day levels. Our temperature estimates are based on an ice-core record of deuterium variations from James Ross Island, off the northeastern tip of the Antarctic Peninsula. We find that the late-Holocene development of ice shelves near James Ross Island was coincident with pronounced cooling from 2,500 to 600 years ago. This cooling was part of a millennial-scale climate excursion with opposing anomalies on the eastern and western sides of the Antarctic Peninsula. Although warming of the northeastern Antarctic Peninsula began around 600 years ago, the high rate of warming over the past century is unusual (but not unprecedented) in the context of natural climate variability over the past two millennia. The connection shown here between past temperature and ice-shelf stability suggests that warming for several centuries rendered ice shelves on the northeastern Antarctic Peninsula vulnerable to collapse. Continued warming to temperatures that now exceed the stable conditions of most of the Holocene epoch is likely to cause ice-shelf instability to encroach farther southward along the Antarctic Peninsula.
Optimized coral reconstructions of the Indian Ocean Dipole: An assessment of location and length considerations
Publisher: American Geophysical Union (AGU)
Date: 10-2015
DOI: 10.1002/2015PA002810
Caves demonstrate decrease in rainfall recharge of southwest Australian groundwater is unprecedented for the last 800 years
Publisher: Springer Science and Business Media LLC
Date: 09-06-2023
DOI: 10.1038/S43247-023-00858-7
Abstract: Billions of people worldwide rely on groundwater. As rainfall in many regions in the future is projected to decrease, it is critical to understand the impacts of climate change on groundwater recharge. The groundwater recharge response to a sustained decrease in rainfall across southwest Australia that began in the late 1960s was examined in seven modern speleothems and drip waters from four caves. These show a pronounced increase or uptick in regional drip water and speleothem oxygen isotopic composition (δ 18 O) that is not driven by a change in rainfall δ 18 O values, but is in response to the shallow karst aquifers becoming disconnected from rainfall recharge due to regional drying. Our findings imply that rainfall recharge to groundwater may no longer be reliably occurring in this region, which is highly dependent on groundwater resources. Examination of the longer speleothem record shows that this situation is unprecedented over the last 800 years.
Advancing community-led research into the climate of the Common Era
Publisher: Copernicus GmbH
Date: 04-03-2021
DOI: 10.5194/EGUSPHERE-EGU21-10979
Abstract: & & The past two thousand years is a key interval for climate science. This period encompasses both the era of human-induced global warming and a much longer interval when changes in Earth& #8217 s climate were governed principally by natural drivers and unforced variability. Since 2009, the Past Global Changes (PAGES) 2k Network has brought together hundreds of scientists from around the world to reconstruct and understand the climate of the Common Era using open and collaborative approaches to palaeoclimate science, including virtual meetings. The third phase of the network will end in December 2021. Here we highlight some key outputs of PAGES 2k and present the major themes and scientific questions emerging from recent surveys of the community. We explore how these might boost a new phase of PAGES 2k or a successor project(s). This year we will further reach out to the community through Town Hall consultations, vEGU and other meetings, and a PAGES 2k global webinar series. The aim of these activities is to foster development of post-2021 community-led PAGES initiatives that connect past and present climate.& &
Supplementary material to "The Iso2k Database: A global compilation of paleo-δ<sup>18</sup>O and δ<sup>2</sup>H records to aid understa
Publisher: Copernicus GmbH
Date: 05-02-2020
Environmental signals in a highly resolved ice core from James Ross Island, Antarctica
Publisher: American Geophysical Union (AGU)
Date: 22-10-2011
DOI: 10.1029/2011JD016147
The preservation of methanesulphonic acid in frozen ice-core samples
Publisher: International Glaciological Society
Date: 2008
DOI: 10.3189/002214308786570890
Abstract: Ice-core records of methanesulphonic acid (MSA) provide a potentially powerful tool for producing proxy records of sea ice, a critical but poorly understood component of the Earth’s climate system. However, MSA is able to diffuse through solid ice, and here we examine the effect of two different methods of frozen storage on the preservation of MSA in archived ice-core s les. Re-analysis of archived ice sticks confirms that MSA diffuses out of ice cores archived in this manner. Despite MSA losses of up to 39% after 7 years storage, the ice sticks studied here preserve much of the variability of the original MSA record, suggesting that useful proxy records can be obtained from archived ice sticks. Furthermore, re-analysis of ice-core s les that had been refrozen into discrete bottled s les for storage demonstrates that it is possible to archive ice s les in a way that prevents MSA loss. In this case, accurate records of MSA variability and concentration were preserved even over storage periods of 15 years. This has important implications for the storage of ice cores and subsequent determination of MSA, and demonstrates that ice storage history needs to be considered when interpreting MSA records.
Author Correction: Coupling of Indo-Pacific climate variability over the last millennium
Publisher: Springer Science and Business Media LLC
Date: 12-01-2022
Antarctic climate variability on regional and continental scales over the last 2000 years
Publisher: Copernicus GmbH
Date: 17-11-2017
Abstract: Abstract. Climate trends in the Antarctic region remain poorly characterized, owing to the brevity and scarcity of direct climate observations and the large magnitude of interannual to decadal-scale climate variability. Here, within the framework of the PAGES Antarctica2k working group, we build an enlarged database of ice core water stable isotope records from Antarctica, consisting of 112 records. We produce both unweighted and weighted isotopic (δ18O) composites and temperature reconstructions since 0 CE, binned at 5- and 10-year resolution, for seven climatically distinct regions covering the Antarctic continent. Following earlier work of the Antarctica2k working group, we also produce composites and reconstructions for the broader regions of East Antarctica, West Antarctica and the whole continent. We use three methods for our temperature reconstructions: (i) a temperature scaling based on the δ18O–temperature relationship output from an ECHAM5-wiso model simulation nudged to ERA-Interim atmospheric reanalyses from 1979 to 2013, and adjusted for the West Antarctic Ice Sheet region to borehole temperature data, (ii) a temperature scaling of the isotopic normalized anomalies to the variance of the regional reanalysis temperature and (iii) a composite-plus-scaling approach used in a previous continent-scale reconstruction of Antarctic temperature since 1 CE but applied to the new Antarctic ice core database. Our new reconstructions confirm a significant cooling trend from 0 to 1900 CE across all Antarctic regions where records extend back into the 1st millennium, with the exception of the Wilkes Land coast and Weddell Sea coast regions. Within this long-term cooling trend from 0 to 1900 CE, we find that the warmest period occurs between 300 and 1000 CE, and the coldest interval occurs from 1200 to 1900 CE. Since 1900 CE, significant warming trends are identified for the West Antarctic Ice Sheet, the Dronning Maud Land coast and the Antarctic Peninsula regions, and these trends are robust across the distribution of records that contribute to the unweighted isotopic composites and also significant in the weighted temperature reconstructions. Only for the Antarctic Peninsula is this most recent century-scale trend unusual in the context of natural variability over the last 2000 years. However, projected warming of the Antarctic continent during the 21st century may soon see significant and unusual warming develop across other parts of the Antarctic continent. The extended Antarctica2k ice core isotope database developed by this working group opens up many avenues for developing a deeper understanding of the response of Antarctic climate to natural and anthropogenic climate forcings. The first long-term quantification of regional climate in Antarctica presented herein is a basis for data–model comparison and assessments of past, present and future driving factors of Antarctic climate.
El Niño Southern Oscillation signal in a new East Antarctic ice core, Mount Brown South
Publisher: Copernicus GmbH
Date: 10-11-2020
DOI: 10.5194/CP-2020-134
Abstract: Abstract. Paleoclimate archives, such as high-resolution ice core records, provide a means to investigate long-term (multi-centennial) climate variability. Until recently, the Law Dome (Dome Summit South) ice core record remained one of few long-term high-resolution records in East Antarctica. A new ice core drilled in 2017/2018 at Mount Brown South, approximately 1000 km west of Law Dome, provides an additional high-resolution record that will likely span the last millennium in the Indian Ocean sector of East Antarctica. Here, we compare snowfall accumulation rates and sea salt concentrations in the upper portion (~21 m) of the Mount Brown South record, and an updated Law Dome record over the period 1975–2016. Annual sea salt concentrations from the Mount Brown South record preserves a stronger signal for the El Niño-Southern Oscillation (ENSO in austral winter and spring, r = 0.521, p
Connections of climate change and variability to large and extreme forest fires in southeast Australia
Publisher: Springer Science and Business Media LLC
Date: 07-01-2021
DOI: 10.1038/S43247-020-00065-8
Abstract: The 2019/20 Black Summer bushfire disaster in southeast Australia was unprecedented: the extensive area of forest burnt, the radiative power of the fires, and the extraordinary number of fires that developed into extreme pyroconvective events were all unmatched in the historical record. Australia’s hottest and driest year on record, 2019, was characterised by exceptionally dry fuel loads that primed the landscape to burn when exposed to dangerous fire weather and ignition. The combination of climate variability and long-term climate trends generated the climate extremes experienced in 2019, and the compounding effects of two or more modes of climate variability in their fire-promoting phases (as occurred in 2019) has historically increased the chances of large forest fires occurring in southeast Australia. Palaeoclimate evidence also demonstrates that fire-promoting phases of tropical Pacific and Indian ocean variability are now unusually frequent compared with natural variability in pre-industrial times. Indicators of forest fire danger in southeast Australia have already emerged outside of the range of historical experience, suggesting that projections made more than a decade ago that increases in climate-driven fire risk would be detectable by 2020, have indeed eventuated. The multiple climate change contributors to fire risk in southeast Australia, as well as the observed non-linear escalation of fire extent and intensity, raise the likelihood that fire events may continue to rapidly intensify in the future. Improving local and national adaptation measures while also pursuing ambitious global climate change mitigation efforts would provide the best strategy for limiting further increases in fire risk in southeast Australia.
Heat and freshwater changes in the Indian Ocean region
Publisher: Springer Science and Business Media LLC
Date: 20-07-2021
Ice core records as sea ice proxies: An evaluation from the Weddell Sea region of Antarctica
Publisher: American Geophysical Union (AGU)
Date: 03-08-2007
DOI: 10.1029/2006JD008139
8-year hydroclimate reconstruction from Christmas Island (Indian Ocean); an extended record of variability in the Indonesian Throughflow
Publisher: Copernicus GmbH
Date: 15-05-2023
DOI: 10.5194/EGUSPHERE-EGU23-11965
Abstract: Future climate trends indicate that changes in temperature and precipitation are likely to influence global supply chains, agricultural productivity, water security, health and well-being particularly in densely populated nations across the southeast Indian Ocean region. The Indonesian Throughflow is an ocean current that transports low-latitude, warm and relatively fresh water from the western Pacific into the eastern Indian Ocean. It is thought that variability and changes in the Indonesian Throughflow have significant impacts on the climate and oceanography of the Indo-Pacific region. The short coverage of observational records makes assessments of hydrological changes across the region challenging on longer timescales, with changes before the 1970s being particularly unreliable. An extended record of Indonesian Throughflow variability needs to be established to contextualise changes and improve model projections of future variability.Christmas Island, located in the southeast Indian Ocean (not to be confused with the Pacific Ocean Kiritimati Island), is located along an outflow of the Indonesian Throughflow. This Island is an ideal location to develop new palaeo-reconstructions of sea surface temperature and hydroclimate, extending our understanding of Indonesian Throughflow variability. Here we present a newly developed coral palaeoclimate reconstruction for Christmas Island, covering the last 118 years at approximately monthly-fortnightly resolution. Corals are sensitive recorders of critical environmental variables, including sea surface temperature and hydroclimate through the analysis of paired stable oxygen isotopes (& #948 O) and trace element (Sr/Ca) ratios. This reconstruction consists of a composite of four newly developed coral records and one previously published record and provides a newly developed & #948 Osw variability record for the region. The newly developed & #948 Osw coral reconstruction correlates strongly with salinity variability, however, presents a weak relationship to in-situ precipitation, indicating that coral hydroclimate reconstructions from Christmas Island likely isolate salinity variability associated with changes in the strength of the Indonesian Throughflow. This relationship highlights the importance that ocean advection plays on & #948 Osw variability at this site. Comparisons to both observational records of the Indonesian throughflow, and previously published coral & #948 Osw records from the Ombai Strait (Timor), a major outflow passage, reveal strong relationships to variability at Christmas Island. The Christmas Island reconstruction provides a unique opportunity to extend current knowledge of the Indonesian Throughflow beyond the observational record. This Christmas Island record also provides an opportunity to evaluate the impact that interannual to multidecadal variability has on the climate across the southeast tropical Indian Ocean.
Influence of long-term changes in solar irradiance forcing on the Southern Annular Mode
Publisher: Copernicus GmbH
Date: 07-2022
Abstract: Abstract. The Southern Annular Mode (SAM) is the leading mode of climate variability in the extratropical Southern Hemisphere, with major regional climate impacts. Observations, reconstructions, and historical climate simulations all show positive trends in the SAM since the 1960s however, earlier trends in palaeoclimate SAM reconstructions cannot be reconciled with last millennium simulations. There are also large differences in the magnitude of solar irradiance change between various solar reconstructions, although most last millennium climate simulations have relied on a low- litude solar-forcing scenario. Here we investigate the sensitivity of the SAM to solar irradiance variations using simulations with a range of constant solar-forcing values and last millennium transient simulations with varying litude solar-forcing scenarios. We find the mean SAM state can be significantly altered by solar irradiance changes and that transient last millennium simulations using a high- litude solar scenario have an improved and significant agreement with proxy-based SAM reconstructions. Our findings suggest that the effects of solar forcing on high-latitude climate may not be adequately incorporated in most last millennium simulations due to solar irradiance changes that are too small and/or the absence of interactive atmospheric chemistry in the global climate models used for these palaeoclimate simulations.
Coupling of Indo-Pacific climate variability over the last millennium
Publisher: Springer Science and Business Media LLC
Date: 09-03-2020
DOI: 10.1038/S41586-020-2084-4
Abstract: The Indian Ocean Dipole (IOD) affects climate and rainfall across the world, and most severely in nations surrounding the Indian Ocean
The CoralHydro2k database: a global, actively curated compilation of coral δ18O and Sr ∕ Ca proxy records of tropical ocean hydrology and temperature for the Common Era
Publisher: Copernicus GmbH
Date: 24-05-2023
DOI: 10.5194/ESSD-15-2081-2023
Abstract: Abstract. The response of the hydrological cycle to anthropogenic climate change, especially across the tropical oceans, remains poorly understood due to the scarcity of long instrumental temperature and hydrological records. Massive shallow-water corals are ideally suited to reconstructing past oceanic variability as they are widely distributed across the tropics, rapidly deposit calcium carbonate skeletons that continuously record ambient environmental conditions, and can be s led at monthly to annual resolution. Climate reconstructions based on corals primarily use the stable oxygen isotope composition (δ18O), which acts as a proxy for sea surface temperature (SST), and the oxygen isotope composition of seawater (δ18Osw), a measure of hydrological variability. Increasingly, coral δ18O time series are paired with time series of strontium-to-calcium ratios (Sr/Ca), a proxy for SST, from the same coral to quantify temperature and δ18Osw variability through time. To increase the utility of such reconstructions, we present the CoralHydro2k database, a compilation of published, peer-reviewed coral Sr/Ca and δ18O records from the Common Era (CE). The database contains 54 paired Sr/Ca–δ18O records and 125 unpaired Sr/Ca or δ18O records, with 88 % of these records providing data coverage from 1800 CE to the present. A quality-controlled set of metadata with standardized vocabulary and units accompanies each record, informing the use of the database. The CoralHydro2k database tracks large-scale temperature and hydrological variability. As such, it is well-suited for investigations of past climate variability, comparisons with climate model simulations including isotope-enabled models, and application in paleodata-assimilation projects. The CoralHydro2k database is available in Linked Paleo Data (LiPD) format with serializations in MATLAB, R, and Python and can be downloaded from the NOAA National Center for Environmental Information's Paleoclimate Data Archive at 0.25921/yp94-v135 (Walter et al., 2022).
Assessing the robustness of Antarctic temperature reconstructions over the past 2 millennia using pseudoproxy and data assimilation experiments
Publisher: Copernicus GmbH
Date: 05-04-2019
Abstract: Abstract. The Antarctic temperature changes over the past millennia remain more uncertain than in many other continental regions. This has several origins: (1) the number of high-resolution ice cores is small, in particular on the East Antarctic plateau and in some coastal areas in East Antarctica (2) the short and spatially sparse instrumental records limit the calibration period for reconstructions and the assessment of the methodologies (3) the link between isotope records from ice cores and local climate is usually complex and dependent on the spatial scales and timescales investigated. Here, we use climate model results, pseudoproxy experiments and data assimilation experiments to assess the potential for reconstructing the Antarctic temperature over the last 2 millennia based on a new database of stable oxygen isotopes in ice cores compiled in the framework of Antarctica2k (Stenni et al., 2017). The well-known covariance between δ18O and temperature is reproduced in the two isotope-enabled models used (ECHAM5/MPI-OM and ECHAM5-wiso), but is generally weak over the different Antarctic regions, limiting the skill of the reconstructions. Furthermore, the strength of the link displays large variations over the past millennium, further affecting the potential skill of temperature reconstructions based on statistical methods which rely on the assumption that the last decades are a good estimate for longer temperature reconstructions. Using a data assimilation technique allows, in theory, for changes in the δ18O–temperature link through time and space to be taken into account. Pseudoproxy experiments confirm the benefits of using data assimilation methods instead of statistical methods that provide reconstructions with unrealistic variances in some Antarctic subregions. They also confirm that the relatively weak link between both variables leads to a limited potential for reconstructing temperature based on δ18O. However, the reconstruction skill is higher and more uniform among reconstruction methods when the reconstruction target is the Antarctic as a whole rather than smaller Antarctic subregions. This consistency between the methods at the large scale is also observed when reconstructing temperature based on the real δ18O regional composites of Stenni et al. (2017). In this case, temperature reconstructions based on data assimilation confirm the long-term cooling over Antarctica during the last millennium, and the later onset of anthropogenic warming compared with the simulations without data assimilation, which is especially visible in West Antarctica. Data assimilation also allows for models and direct observations to be reconciled by reproducing the east–west contrast in the recent temperature trends. This recent warming pattern is likely mostly driven by internal variability given the large spread of in idual Paleoclimate Modelling Intercomparison Project (PMIP)/Coupled Model Intercomparison Project (CMIP) model realizations in simulating it. As in the pseudoproxy framework, the reconstruction methods perform differently at the subregional scale, especially in terms of the variance of the time series produced. While the potential benefits of using a data assimilation method instead of a statistical method have been highlighted in a pseudoproxy framework, the instrumental series are too short to confirm this in a realistic setup.
Variability of sea‐ice in the northern W eddell S ea during the 20th century
Publisher: American Geophysical Union (AGU)
Date: 07-2014
DOI: 10.1002/2013JC009511
Increasing intensity and frequency of cold fronts contributed to Australia’s 2019–2020 Black Summer fire disaster
Publisher: IOP Publishing
Date: 09-2022
Abstract: Human-caused climate changes are increasing the risk of dangerous wildfires in many regions of the world. There are multiple, compounding aspects of climate change that are increasing fire risk, including large-scale climate changes driving hotter and drier conditions that are generally well observed and predicted. However, changes in synoptic-scale processes that can exacerbate dangerous fire weather and promote extreme pyroconvective events are often not well known in historical observations and are poorly represented in climate models, making it difficult to fully quantify and anticipate changing fire risk. In this study, we statistically test the association between synoptic-scale cold front passage and large fires in southeast Australia during Australia’s 2019–2020 ‘Black Summer’ fire disaster, and analyse daily gridded temperature data to detect long-term changes in the intensity and frequency of strong cold fronts over southeast Australia. We demonstrate that the passage of cold fronts over southeast Australia significantly increased the likelihood of large fire days during the entire Black Summer fire season. Additionally, the intensity and frequency of strong cold front events were anomalously high during the Black Summer, and this is part of a long-term significant increase in the intensity and frequency of strong cold fronts since the 1950s. These changes in fire-promoting cold front activity are expected to imminently emerge above the range of historical experience across large areas of southeast Australia if current trends continue. Our results provide new insights into a previously poorly constrained contributor to fire risk in southeast Australia, highlighting the potential of synoptic-scale weather changes to compound previously documented broad-scale climate changes in intensifying future forest fire risk.
Identifying atmospheric processes favouring the formation of bubble free layers in Law Dome ice core, East Antarctica
Publisher: Copernicus GmbH
Date: 03-04-2023
DOI: 10.5194/EGUSPHERE-2023-611
Abstract: Abstract. Physical features preserved in ice cores may provide unique records about past atmospheric variability. Linking the formation and preservation of these features and the atmospheric processes causing them is key to their interpretation as paleoclimate proxies. We imaged ice cores from Law Dome, East Antarctica using an Intermediate Layer Ice Core Scanner (ILCS) which shows that thin bubble-free layers (BFLs) occur multiple times per year at this site. The origin of these features is unknown. We used a previously developed age-depth scale in conjunction with regional accumulation estimated from atmospheric reanalysis data (ERA5) to estimate the year and month that the BFLs occurred, and then performed seasonal and annual analysis to reduce the overall dating errors. We then investigated measurements of snow surface height from a co-located automatic weather station to determine snow surface features co-occurring with BFLs, as well as their estimated occurrence date. We also used ERA5 to investigate potentially relevant local/regional atmospheric processes (temperature inversions, wind scour, accumulation hiatuses and extreme precipitation) associated with BFL occurrence. Finally, we used a synoptic typing dataset of the southern Indian and southwest Pacific Oceans to investigate the relationship between large scale atmospheric patterns and BFL occurrence. Our results show that BFLs occur (1) primarily in autumn and winter, (2) in conjunction with accumulation hiatuses days, and (3) during synoptic patterns characterised by meridional atmospheric flow related to the episodic blocking and channeling of maritime moisture to the ice core site. Thus, BFLs may act as a seasonal marker (autumn/winter), and may indicate episodic changes in accumulation (such as hiatuses) associated with large-scale circulation. This study provides a pathway to the development of a new proxy for past climate in the Law Dome ice cores specifically past snowfall conditions relating to synoptic variability over the southern Indian Ocean.
Images of diagenetic textures in Porites corals from Papua New Guinea and Indonesia
Publisher: American Geophysical Union (AGU)
Date: 10-2008
DOI: 10.1029/2008GC002093
Sclerochronology
Publisher: Springer Netherlands
Date: 2011
Ubiquitous karst hydrological control on speleothem oxygen isotope variability in a global study
Publisher: Springer Science and Business Media LLC
Date: 15-02-2022
DOI: 10.1038/S43247-022-00347-3
Abstract: Speleothem oxygen isotopic (δ 18 O) records are used to reconstruct past hydroclimate yet records from the same cave do not always replicate. We use a global database of speleothem δ 18 O to quantify the replicability of records to show that disagreement is common worldwide, occurs across timescales and is unrelated to climate, depth or lithology. Our global analysis demonstrates that within-cave differences in mean speleothem δ 18 O values are consistent with those of dripwater, supporting a ubiquitous influence of flowpaths. We present a case study of four new stalagmite records from Golgotha Cave, southwest Australia, where the isotopic differences between them are informed by cave monitoring. It is demonstrated that karst hydrology is a major driver of within-cave speleothem and dripwater δ 18 O variability, primarily due to the influence of fractures on flowpaths. Applying our understanding of water movement through fractures assists in quantitative reconstruction of past climate variability from speleothem δ 18 O records.
Technical note: Open-paleo-data implementation pilot – the PAGES 2k special issue
Publisher: Copernicus GmbH
Date: 03-05-2018
Abstract: Abstract. Data stewardship is an essential element of the publication process. Knowing how to enact data polices that are described only in general terms can be difficult, however. Ex les are needed to model the implementation of open-data polices in actual studies. Here we explain the procedure used to attain a high and consistent level of data stewardship across a special issue of the journal Climate of the Past. We discuss the challenges related to (1) determining which data are essential for public archival, (2) using data generated by others, and (3) understanding data citations. We anticipate that open-data sharing in paleo sciences will accelerate as the advantages become more evident and as practices that reduce data loss become the accepted convention.
Back to the Future: Using Long-Term Observational and Paleo-Proxy Reconstructions to Improve Model Projections of Antarctic Climate
Publisher: MDPI AG
Date: 07-06-2019
DOI: 10.3390/GEOSCIENCES9060255
Abstract: Quantitative estimates of future Antarctic climate change are derived from numerical global climate models. Evaluation of the reliability of climate model projections involves many lines of evidence on past performance combined with knowledge of the processes that need to be represented. Routine model evaluation is mainly based on the modern observational period, which started with the establishment of a network of Antarctic weather stations in 1957/58. This period is too short to evaluate many fundamental aspects of the Antarctic and Southern Ocean climate system, such as decadal-to-century time-scale climate variability and trends. To help address this gap, we present a new evaluation of potential ways in which long-term observational and paleo-proxy reconstructions may be used, with a particular focus on improving projections. A wide range of data sources and time periods is included, ranging from ship observations of the early 20th century to ice core records spanning hundreds to hundreds of thousands of years to sediment records dating back 34 million years. We conclude that paleo-proxy records and long-term observational datasets are an underused resource in terms of strategies for improving Antarctic climate projections for the 21st century and beyond. We identify priorities and suggest next steps to addressing this.
Palaeoclimate: Climate's playground
Publisher: Springer Science and Business Media LLC
Date: 12-12-2017
DOI: 10.1038/NGEO2856
Automated ice-core layer-counting with strong univariate signals
Publisher: Copernicus GmbH
Date: 22-11-2012
Abstract: Abstract. We present an automated process for determining the annual layer chronology of an ice-core with a strong annual signal, utilising the hydrogen peroxide record from an Antarctic Peninsula ice-core as a test signal on which to count annual cycles and explain the methods. The signal is de-trended and normalised before being split into sections with a deterministic cycle count and those that need more attention. Possible reconstructions for the uncertain sections are determined which could be used as a visual aid for manual counting, and a simple method for assigning probability measures to each reconstruction is discussed. The robustness of this process is explored by applying it to versions of two different chemistry signals from the same stretch of the NGRIP (North Greenland Ice Core Project) ice-core, which shows more variation in annual layer thickness, with and without thinning to mimic poorer quality data. An adapted version of these methods is applied to the more challenging non-sea-salt sulphur signal from the same Antarctic Peninsula core from which the hydrogen peroxide signal was taken. These methods could readily be adapted for use on much longer datasets, thereby reducing manual effort and providing a robust automated layer-counting methodology.
El Niño–Southern Oscillation signal in a new East Antarctic ice core, Mount Brown South
Publisher: Copernicus GmbH
Date: 09-09-2021
Abstract: Abstract. Paleoclimate archives, such as high-resolution ice core records, provide a means to investigate past climate variability. Until recently, the Law Dome (Dome Summit South site) ice core record remained one of few millennial-length high-resolution coastal records in East Antarctica. A new ice core drilled in 2017/2018 at Mount Brown South, approximately 1000 km west of Law Dome, provides an additional high-resolution record that will likely span the last millennium in the Indian Ocean sector of East Antarctica. Here, we compare snow accumulation rates and sea salt concentrations in the upper portion (∼ 20 m) of three Mount Brown South ice cores and an updated Law Dome record over the period 1975–2016. Annual sea salt concentrations from the Mount Brown South site record preserve a stronger signal for the El Niño–Southern Oscillation (ENSO austral winter and spring, r = 0.533, p 0.001, Multivariate El Niño Index) compared to a previously defined Law Dome record of summer sea salt concentrations (November–February, r = 0.398, p = 0.010, Southern Oscillation Index). The Mount Brown South site record and Law Dome record preserve inverse signals for the ENSO, possibly due to longitudinal variability in meridional transport in the southern Indian Ocean, although further analysis is needed to confirm this. We suggest that ENSO-related sea surface temperature anomalies in the equatorial Pacific drive atmospheric teleconnections in the southern mid-latitudes. These anomalies are associated with a weakening (strengthening) of regional westerly winds to the north of Mount Brown South that correspond to years of low (high) sea salt deposition at Mount Brown South during La Niña (El Niño) events. The extended Mount Brown South annual sea salt record (when complete) may offer a new proxy record for reconstructions of the ENSO over the recent millennium, along with improved understanding of regional atmospheric variability in the southern Indian Ocean, in addition to that derived from Law Dome.
A review of past and projected changes in Australia's rainfall
Publisher: Wiley
Date: 07-03-2019
DOI: 10.1002/WCC.577
Abstract: There has been much attention given to the spatial and temporal characteristics of changes in mean and extreme rainfall over Australia during the past century. As Australia is the second driest continent on Earth, reliable projections around the trends and variability in future rainfall are crucial for policymakers and water resource management. This article comprehensively reviews the current published literature on trends in Australia's rainfall from pre‐instrumental and instrumental records, the climatic drivers of Australia's rainfall variability, attribution of the long‐term trends, extreme rainfall attribution methods with particular reference to a recent case study (2010–2012 east Australia rainfall event) and projected changes of mean and extreme rainfall over Australia during the 21st century. Notable trends in the observational record of rainfall in Australia are a decrease in mean rainfall in southwest and southeast Australia and an increase in northwest Australia since 1950. The general consensus of research into Australia's future rainfall is that mean rainfall will continue to decrease in southwest Australia in a warming world, while changes over northern and eastern Australia remain uncertain. There are still significant knowledge gaps around the causes of observed trends in rainfall both in the mean and extremes, the ability of climate models to accurately represent rainfall in the Australian region and future rainfall projections. These gaps are identified, and avenues for future research directions are proposed. This article is categorized under: Paleoclimates and Current Trends Modern Climate Change
Stable isotopes and trace elements
Publisher: Springer Netherlands
Date: 2011
Tropical Pacific variability and anthropogenic forcing are the key drivers of the West Antarctic atmospheric circulation variability over the 20th century
Publisher: Copernicus GmbH
Date: 15-05-2023
DOI: 10.5194/EGUSPHERE-EGU23-683
Abstract: The future evolution of the West Antarctic Ice Sheet (WAIS) will strongly influence the global sea-level rise in the coming decades. Ice shelf melting in that sector is partly controlled by the low-pressure system located off the West Antarctic coast, namely the Amundsen Sea Low (ASL). When the ASL is deep, an overall increase in ice shelf melting is noticed. Because of the sparse observational network and the strong internal variability, our understanding of the long-term climate changes in the atmospheric circulation is limited, and therefore its impact on ice melting as well. Among all the processes involved in the West Antarctic climate variability, an increasing number of studies have pointed out the strong impact of the climate in the tropical Pacific. However, most of those studies focus on the past decades, which prevents the analysis of the role of the multi-decadal tropical variability on the West Antarctic climate. Here, we combine annually-resolved paleoclimate records, in particular ice core and coral records, and the physics of climate models through paleoclimate data assimilation to provide a complete spatial multi-field reconstruction of climate variability in the tropics and Antarctic. This allows for studying both the year-to-year and multi-decadal variability of the tropical-Antarctic teleconnections. As data assimilation provides a climate reconstruction that is dynamically constrained, the contribution of the tropical variability on the West Antarctic climate changes can be directly assessed. Our results indicate that climate variability in the tropical Pacific is the main driver of ASL variability at the multi-decadal time scale, with a strong link to the Interdecadal Pacific Oscillation (IPO). However, the deepening of the Amundsen Sea Low over the 20th century cannot be explained by tropical climate variability. By using large ensembles of climate model simulations, our analysis suggests anthropogenic forcing as the primary driver of this 20th century ASL deepening. In summary, the 20th century ASL deepening is explained by the forcing, but the multi-decadal variability related to the& IPO is superimposed on this long-term trend.
Assessing recent trends in high-latitude Southern Hemisphere surface climate
Publisher: Springer Science and Business Media LLC
Date: 28-09-2016
DOI: 10.1038/NCLIMATE3103
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.
Potential and limitations of marine and ice core sea ice proxies: an example from the Indian Ocean sector
Publisher: Elsevier BV
Date: 2010
19th century glacier retreat in the Alps preceded the emergence of industrial black carbon deposition on high-alpine glaciers
Publisher: Copernicus GmbH
Date: 16-10-2018
Abstract: Abstract. Light absorbing aerosols in the atmosphere and cryosphere play an important role in the climate system. Their presence in ambient air and snow changes the radiative properties of these systems, thus contributing to increased atmospheric warming and snowmelt. High spatio-temporal variability of aerosol concentrations and a shortage of long-term observations contribute to large uncertainties in properly assigning the climate effects of aerosols through time. Starting around AD 1860, many glaciers in the European Alps began to retreat from their maximum mid-19th century terminus positions, thereby visualizing the end of the Little Ice Age in Europe. Radiative forcing by increasing deposition of industrial black carbon to snow has been suggested as the main driver of the abrupt glacier retreats in the Alps. The basis for this hypothesis was model simulations using elemental carbon concentrations at low temporal resolution from two ice cores in the Alps. Here we present sub-annually resolved concentration records of refractory black carbon (rBC using soot photometry) as well as distinctive tracers for mineral dust, biomass burning and industrial pollution from the Colle Gnifetti ice core in the Alps from AD 1741 to 2015. These records allow precise assessment of a potential relation between the timing of observed acceleration of glacier melt in the mid-19th century with an increase of rBC deposition on the glacier caused by the industrialization of Western Europe. Our study reveals that in AD 1875, the time when rBC ice-core concentrations started to significantly increase, the majority of Alpine glaciers had already experienced more than 80 % of their total 19th century length reduction, casting doubt on a leading role for soot in terminating of the Little Ice Age. Attribution of glacial retreat requires expansion of the spatial network and s ling density of high alpine ice cores to balance potential biasing effects arising from transport, deposition, and snow conservation in in idual ice-core records.
Hemispheric black carbon increase after the 13th-century Māori arrival in New Zealand
Publisher: Springer Science and Business Media LLC
Date: 06-10-2021
Contribution of tropical variability on Antarctic climate changes over the past centuries
Publisher: Copernicus GmbH
Date: 27-03-2022
DOI: 10.5194/EGUSPHERE-EGU22-5596
Abstract: & & The future evolution of the Antarctic Ice Sheet (AIS), particularly the West Antarctic Ice Sheet (WAIS), will strongly influence global sea-level rise during the 21& sup& st& /sup& century and beyond. However, because of the sparse observational network in concert with the strong internal variability, our understanding of the long-term climate and ice sheet changes in the Antarctic is limited. Among all the processes involved in Antarctic climate variability and change, an increasing number of studies have pointed out the strong relationship between the climate in the tropics and Antarctic (also called tropical-Antarctic teleconnections), especially between the Pacific Ocean and the West Antarctic region. Most of those studies focus only on the past decades, but to fully understand the long-term Antarctic climate changes associated with tropical variability longer time-series are needed. This is achieved here by using annually-resolved paleoclimate records (ice core and coral records) that cover at least the last two centuries to study both the year-to-year and multi-decadal variability of tropical-Antarctic teleconnections. These records are incorporated into a data assimilation framework that optimally combines the paleoclimate records with the physics of the climate model. As data assimilation provides a climate reconstruction that is dynamically constrained & #8211 through the spatial covariance in the climate model & #8211 the contribution of tropical variability on Antarctic climate changes can be directly assessed. Different sensitivity tests are performed to isolate the contribution of each tropical basin. Additionally, the roles of multi-decadal and year-to-year variability are compared by averaging the annual paleoclimate records at a lower temporal resolution. This new method of combining the two time-scales is proposed in order to preserve the multi-decadal variability in the annual climate reconstruction.& &
An annually resolved chronology for the Mount Brown South ice cores, East Antarctica
Publisher: Copernicus GmbH
Date: 25-07-2023
DOI: 10.5194/CP-2023-52
Abstract: Abstract. Climate reconstructions of the last millennium rely on networks of high resolution and well-dated proxy records. This study presents age-at-depth data and preliminary results from the new Mount Brown South ice cores, collected at an elevation of 2,084 metres on the boundary of Princess Elizabeth and Kaiser Wilhelm II Land in East Antarctica. We show an initial analysis of the site meteorology, mean annual chemical species concentrations, and seasonal cycles including analysis of a seasonal cycle in fluoride concentrations with a potential link to sea ice formation. The annually resolved chronologies were developed from this data using a site-specific layer-counting methodology which employed seasonally varying trace chemical species and water isotope ratios, combined with a volcanic horizon alignment approach. The chronologies developed include the ‘Main’ 295 m record spanning 1,137 years (873–2009 CE), and three surface cores spanning the most recent 39–52 years up to the surface age at the time of drilling (austral summer 2017/2018). Mean annual trace chemical concentrations are compared to the Law Dome ice core further to the east and discussed in terms of atmospheric transport, and the uncertainty in the determination of annual horizons via layer counting is quantified. The MBS chronologies presented here – named MBS2023 – will underpin the development of new palaeoclimate records spanning the past millennium from this under-represented region of East Antarctica.
Assessing the robustness of Antarctic temperature reconstructions over the past two millennia using pseudoproxy and data assimilation experiments
Publisher: Copernicus GmbH
Date: 14-08-2018
DOI: 10.5194/CP-2018-90
Abstract: Abstract. The Antarctic temperature changes over the past millennia remain more uncertain than in many other continental regions. This has several origins: 1) the number of high resolution ice cores is small, in particular on the Antarctic Plateau and in some coastal areas in East Antarctica 2) the short instrumental records limit the calibration period for reconstructions and the assessment of the methodologies 3) the link between isotope records from ice cores and local climate is usually complex and dependent on the spatial and time scales investigated. Here, we use climate model results, pseudoproxy and data assimilation experiments to assess the potential of reconstructing the Antarctic temperature over the last two millennia based on a new database of stable oxygen isotopes in ice cores compiled in the framework of Antarctica2k (Stenni et al., 2017). The well-known covariance between δ18O and temperature is reproduced in the two isotope-enabled models used (ECHAM5/MPI-OM and ECHAM5-wiso), but is generally weak over the different Antarctic regions, limiting the skill of the reconstructions. Furthermore, the strength of the link displays large variations over the past millennium, further affecting the potential skill of temperature reconstructions based on statistical methods which rely on the assumption that the last decades are a good estimate for longer temperature reconstructions. Using a data assimilation technique allows in theory taking into account changes in the δ18O-temperature link through time and space. Pseudoproxy experiments confirm the benefits of using data assimilation methods instead of statistical ones that provide reconstructions with unrealistic variances in some Antarctic subregions. They also confirm that the relatively weak link between both variables leads to a limited potential for reconstructing temperature based on δ18O. The reconstruction skill is however higher and more uniform among reconstruction methods when the reconstruction target is the Antarctic as a whole rather than smaller Antarctic subregions. This consistency between the methods at the large scale is also observed when reconstructing temperature based on the real δ18O regional composites of Stenni et al. (2017). In this case, temperature reconstructions based on data assimilation confirm the long term cooling over Antarctica during the last millennium, and the later onset of anthropogenic warming compared to the simulations without data assimilation, especially visible in West Antarctica. Data assimilation also allows reconciling models and direct observations by reconstructing the East-West contrast regarding the recent temperature trends, indicating that internal variability likely plays a major role in driving this heterogeneous recent warming. This is further supported by the large spread of in idual PMIP/CMIP model realizations regarding the recent warming pattern. As in the pseudoproxy framework, the reconstruction methods perform differently at the subregional scale, especially in terms of the variance of the produced time series. While the potential benefits of using a data assimilation method instead of a statistical one have been highlighted in a pseudoproxy framework, the instrumental series are too short to confirm it in a realistic setup.
Caves provide early warning of unprecedented decrease in rainfall recharge of groundwater
Publisher: Research Square Platform LLC
Date: 02-05-2022
DOI: 10.21203/RS.3.RS-1556439/V1
Abstract: Billions of people worldwide rely on groundwater. As rainfall in many regions in the future is projected to decrease, it is critical to understand the impacts of climate change on groundwater recharge. In this study, five caves record a consistent response to a sustained decrease in rainfall across southwest Australia that began in the late 1960s, characterised by a pronounced increase or ’uptick’ in dripwater and speleothem oxygen isotopic composition (δ18O). It is demonstrated that the uptick is in response to the shallow karst aquifers becoming disconnected from recharge due to regional drying. Our findings imply that rainfall recharge to groundwater across this region is no longer reliably occurring. Examination of the longer speleothem record shows that this is unprecedented over at least the last 800 years. A global network of cave dripwater monitoring would serve as an early warning of reduced groundwater recharge elsewhere, while evidence for upticks in speleothem paleoclimate records would provide a longer-term context to evaluate if current groundwater recharge changes are outside the range of natural variability. This study also validates speleothems as recorders of past hydroclimate via lification of the δ18O signal by karst hydrology highlighting that speleothem δ18O are records of recharge, rather than a direct proxy for rainfall.
Intensified decadal variability in tropical climate during the late 19th century
Publisher: American Geophysical Union (AGU)
Date: 04-2009
DOI: 10.1029/2008GL036924
Influence of long-term changes in solar irradiance forcing on the Southern Annular Mode
Publisher: Copernicus GmbH
Date: 29-11-2021
DOI: 10.5194/CP-2021-156
Abstract: Abstract. The Southern Annular Mode (SAM) is the leading mode of climate variability in the extratropical Southern Hemisphere, with major regional climate impacts. Observations, reconstructions, and historical climate simulations all show positive trends in the SAM since the 1960s however, earlier trends in palaeoclimate SAM reconstructions cannot be reconciled with last millennium simulations. Here we investigate the sensitivity of the SAM to solar irradiance variations using simulations with a range of constant solar forcing values, and last millennium transient simulations with varying litude solar forcing scenarios. We find the mean SAM state can be significantly altered by solar irradiance changes, and that transient last millennium simulations using a high- litude solar scenario have an improved and significant agreement with proxy-based SAM reconstructions. Our findings suggest that the effects of solar forcing on high-latitude climate may not be adequately incorporated in most last millennium simulations, due to solar irradiance changes that are too small and/or the absence of interactive atmospheric chemistry in global climate models.
Spatio-temporal evolution of Australasian monsoon hydroclimate over the last 40,000 years
Publisher: Elsevier BV
Date: 05-2019
Antarctic climate variability at regional and continental scales over the last 2,000 years
Publisher: Copernicus GmbH
Date: 22-03-2017
DOI: 10.5194/CP-2017-40
Abstract: Abstract. Climate trends in the Antarctic region remain poorly characterised, owing to the brevity and scarcity of direct climate observations and the large magnitude of interannual to decadal-scale climate variability. Here, within the framework of the PAGES Antarctica 2k working group, we build an enlarged database of ice core water stable isotope records from Antarctica, consisting of 112 records. We produce both unweighted and weighted isotopic (δ18O) composites and temperature reconstructions since 0 CE, binned at 5 and 10-year resolution, for 7 climatically-distinct regions covering the Antarctic continent. Following earlier work of the Antarctica 2k working group, we also produce composites and reconstructions for the broader regions of East Antarctica, West Antarctica, and the whole continent. We use three methods for our temperature reconstructions: i) a temperature scaling based on the δ18O-temperature relationship output from an ECHAM5-wiso model simulation nudged to ERA-interim atmospheric reanalyses from 1979 to 2013, and adjusted for the West Antarctic Ice Sheet region to borehole temperature data ii) a temperature scaling of the isotopic normalized anomalies to the variance of the regional reanalysis temperature and iii) a composite-plus-scaling approach used in a previous continental scale reconstruction of Antarctic temperature since 1 CE but applied to the new Antarctic ice core database. Our new reconstructions confirm a significant cooling trend from 0 to 1900 CE across all Antarctic regions where records extend back into the 1st millennium, with the exception of the Wilkes Land coast and Weddell Sea coast regions. Within this long-term cooling trend from 0–1900 CE we find that the warmest period occurs between 300 and 1000 CE, and the coldest interval from 1200 to 1900 CE. Since 1900 CE, significant warming trends are identified for the West Antarctic Ice Sheet, the Dronning Maud Land coast and the Antarctic Peninsula regions, and these trends are robust across the distribution of records that contribute to the unweighted isotopic composites and also significant in the weighted temperature reconstructions. Only for the Antarctic Peninsula is this most recent century-scale trend unusual in the context of natural variability over the last 2000-years. However, projected warming of the Antarctic continent during the 21st Century may soon see significant and unusual warming develop across other parts of the Antarctic continent. The extended Antarctica 2k ice core isotope database developed by this working group opens up many avenues for developing a deeper understanding of the response of Antarctic climate to natural and anthropogenic climate forcings. The first long-term quantification of regional climate in Antarctica presented herein is a basis for data-model comparison and assessments of past, present and future driving factors of Antarctic climate.
High resolution aerosol concentration data from the Greenland NorthGRIP and NEEM deep ice cores
Publisher: Copernicus GmbH
Date: 20-10-2021
Abstract: Abstract. Records of chemical impurities from ice cores enable us to reconstruct the past deposition of aerosols onto the polar ice sheets and alpine glaciers. Through that, they allow us to gain insight into changes of the source, transport and deposition processes that ultimately determine the deposition flux at the coreing location. However, the low concentrations of the aerosol species in the ice and the resulting high risk of contamination poses a formidable analytical challenge, especially if long, continuous and highly resolved records are needed. Continuous Flow Analysis, CFA, the continuous melting, decontamination and analysis of ice-core s les has mostly overcome this issue and has quickly become the de-facto standard to obtain high-resolution aerosol records from ice cores after its inception at the University of Bern in the mid 90s. Here we present continuous records of calcium (Ca2+), sodium (Na+), ammonium (NH4+), nitrate (NO3−1) and electrolytic conductivity at 1 mm depth resolution from the NGRIP (North Greenland Ice Core Project) and NEEM (North Greenland Eemian Ice Drilling) ice cores produced by the Bern Continuous Flow Analysis group in the years 2000 to 2011. Both of the records have previously been used in a number of studies but have never been published in the full 1 mm resolution. Alongside the 1 mm datasets we provide decadal averages, a detailed description of the methods, relevant references, an assessment of the quality of the data and its usable resolution. Along the way we will also give some historical context on the development of the Bern CFA system.
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.
Ice core reconstruction of sea ice change in the Amundsen‐Ross Seas since 1702 A.D.
Publisher: American Geophysical Union (AGU)
Date: 23-05-2016
DOI: 10.1002/2016GL068130
Is XRF core scanning a viable method for coral palaeoclimate temperature reconstructions?
Publisher: Elsevier BV
Date: 04-2019
Reconstructed streamflow for Citarum River, Java, Indonesia: linkages to tropical climate dynamics
Publisher: Springer Science and Business Media LLC
Date: 11-12-2009
Teleconnection stationarity, variability and trends of the Southern Annular Mode (SAM) during the last millennium
Publisher: Springer Science and Business Media LLC
Date: 30-11-2017
Ice core evidence for a 20th century decline of sea ice in the Bellingshausen Sea, Antarctica
Publisher: American Geophysical Union (AGU)
Date: 12-2010
DOI: 10.1029/2010JD014644
El Niño–Southern Oscillation variability, teleconnection changes and responses to large volcanic eruptions since AD 1000
Publisher: Wiley
Date: 05-02-2019
DOI: 10.1002/JOC.5983
Biological response of coral reefs to sea surface temperature variation: Evidence from the raised Holocene reefs of Kikai-jima (Ryukyu Islands, Japan)
Publisher: Springer Science and Business Media LLC
Date: 11-2001
Author Correction: Palaeoclimate constraints on the impact of 2 °C anthropogenic warming and beyond
Publisher: Springer Science and Business Media LLC
Date: 18-07-2018
Past warming events in the Arctic linked to shifting winds in the Antarctic
Publisher: Springer Science and Business Media LLC
Date: 11-2018
The Iso2k database: a global compilation of paleo-<i>δ</i><sup>18</sup>O and <i>δ</i><sup>2</s
Publisher: Copernicus GmbH
Date: 23-09-2020
DOI: 10.5194/ESSD-12-2261-2020
Abstract: Abstract. Reconstructions of global hydroclimate during the Common Era (CE the past ∼2000 years) are important for providing context for current and future global environmental change. Stable isotope ratios in water are quantitative indicators of hydroclimate on regional to global scales, and these signals are encoded in a wide range of natural geologic archives. Here we present the Iso2k database, a global compilation of previously published datasets from a variety of natural archives that record the stable oxygen (δ18O) or hydrogen (δ2H) isotopic compositions of environmental waters, which reflect hydroclimate changes over the CE. The Iso2k database contains 759 isotope records from the terrestrial and marine realms, including glacier and ground ice (210) speleothems (68) corals, sclerosponges, and mollusks (143) wood (81) lake sediments and other terrestrial sediments (e.g., loess) (158) and marine sediments (99). In idual datasets have temporal resolutions ranging from sub-annual to centennial and include chronological data where available. A fundamental feature of the database is its comprehensive metadata, which will assist both experts and nonexperts in the interpretation of each record and in data synthesis. Key metadata fields have standardized vocabularies to facilitate comparisons across erse archives and with climate-model-simulated fields. This is the first global-scale collection of water isotope proxy records from multiple types of geological and biological archives. It is suitable for evaluating hydroclimate processes through time and space using large-scale synthesis, model–data intercomparison and (paleo)data assimilation. The Iso2k database is available for download at 0.25921/57j8-vs18 (Konecky and McKay, 2020) and is also accessible via the NOAA/WDS Paleo Data landing page: aleo/study/29593 (last access: 30 July 2020).
Discovery of an ergosterol-signaling factor that regulates Trypanosoma brucei growth
Publisher: Elsevier BV
Date: 02-2015
DOI: 10.1194/JLR.M054643
A review of sea ice proxy information from polar ice cores
Publisher: Elsevier BV
Date: 11-2013
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”.
Technical Note: A best-practice approach to calculating the Southern Annular Mode index
Publisher: Copernicus GmbH
Date: 17-08-2023
DOI: 10.5194/CP-2023-64
Abstract: Abstract. The Southern Annular Mode (SAM) strongly influences climate variability in the Southern Hemisphere. The SAM index describes the phase and magnitude of the SAM and can be calculated by measuring the difference in mean sea level pressure (MSLP) between mid- and high-latitudes. This study investigates the effects of calculation methods and data resolution on the SAM index, and subsequent interpretations of SAM impacts and trends. We show that the normalisation step that is traditionally used in calculating a non-dimensional SAM index leads to substantial differences in the magnitude of the SAM index calculated at different temporal resolutions, and that the equal weighting given to MSLP variability at the mid and high southern latitudes artificially alters temperature and precipitation correlations and the interpretation of climate change trends in the SAM. These issues can be overcome by instead using a dimensional formulation of the SAM based on MSLP anomalies, resulting in consistent scaling and variability of the SAM index calculated at daily, monthly and annual data resolutions. The 10 dimensional version of the SAM index has improved representation of SAM impacts in the high southern latitudes, including the asymmetric (zonal wave-3) component of MSLP variability, whereas the increased weighting given to mid-latitude MSLP variability in the non-dimensional SAM incorporates a stronger component of tropical climate variability that is not directly associated with SAM variability. We conclude that a best-practice approach of calculating the SAM index as a dimensional index derived from MSLP anomalies would aid consistency across climate studies and avoid potential ambiguity in the SAM 15 index, including SAM index reconstructions from paleoclimate data, and enable more consistent interpretations of SAM trends and impacts.
Reversible interconversion of carbon dioxide and formate by an electroactive enzyme
Publisher: Proceedings of the National Academy of Sciences
Date: 05-08-2008
Abstract: Carbon dioxide (CO 2 ) is a kinetically and thermodynamically stable molecule. It is easily formed by the oxidation of organic molecules, during combustion or respiration, but is difficult to reduce. The production of reduced carbon compounds from CO 2 is an attractive proposition, because carbon-neutral energy sources could be used to generate fuel resources and sequester CO 2 from the atmosphere. However, available methods for the electrochemical reduction of CO 2 require excessive overpotentials (are energetically wasteful) and produce mixtures of products. Here, we show that a tungsten-containing formate dehydrogenase enzyme (FDH1) adsorbed to an electrode surface catalyzes the efficient electrochemical reduction of CO 2 to formate. Electrocatalysis by FDH1 is thermodynamically reversible—only small overpotentials are required, and the point of zero net catalytic current defines the reduction potential. It occurs under thoroughly mild conditions, and formate is the only product. Both as a homogeneous catalyst and on the electrode, FDH1 catalyzes CO 2 reduction with a rate more than two orders of magnitude faster than that of any known catalyst for the same reaction. Formate oxidation is more than five times faster than CO 2 reduction. Thermodynamically, formate and hydrogen are oxidized at similar potentials, so formate is a viable energy source in its own right as well as an industrially important feedstock and a stable intermediate in the conversion of CO 2 to methanol and methane. FDH1 demonstrates the feasibility of interconverting CO 2 and formate electrochemically, and it is a template for the development of robust synthetic catalysts suitable for practical applications.
Coral radiocarbon records of Indian Ocean water mass mixing and wind‐induced upwelling along the coast of Sumatra, Indonesia
Publisher: American Geophysical Union (AGU)
Date: 05-2004
DOI: 10.1029/2003JC002087
Optimal site selection for a high resolution ice core record in East Antarctica
Publisher: Copernicus GmbH
Date: 03-11-2015
Abstract: Abstract. Ice cores provide some of the best dated and most comprehensive proxy records, as they yield a vast and growing array of proxy indicators. Selecting a site for ice core drilling is nonetheless challenging, as the assessment of potential new sites needs to consider a variety of factors. Here, we demonstrate a systematic approach to site selection for a new East Antarctic high resolution ice core record. Specifically, seven criteria are considered: (1) 2000 year old ice at 300 m depth, (2) above 1000 m elevation, (3) a minimum accumulation rate of 250 mm yr−1 IE, (4) minimal surface re-working to preserve the deposited climate signal, (5) a site with minimal displacement or elevation change of ice at 300 m depth, (6) a strong teleconnection to mid-latitude climate and (7) an appropriately complementary relationship to the existing Law Dome record (a high resolution record in East Antarctica). Once assessment of these physical characteristics identified promising regions, logistical considerations (for site access and ice core retrieval) were briefly considered. We use Antarctic surface mass balance syntheses, along with ground-truthing of satellite data by airborne radar surveys to produce all-of-Antarctica maps of surface roughness, age at specified depth, elevation and displacement change and surface air temperature correlations to pinpoint promising locations. We also use the European Centre for Medium-Range Weather Forecast ERA 20th Century reanalysis (ERA-20C) to ensure a site complementary to the Law Dome record is selected. We find three promising sites in the Indian Ocean sector of East Antarctica in the coastal zone from Enderby Land to the Ingrid Christensen Coast (50–100° E). Although we focus on East Antarctica for a new ice core site, the methodology is more generally applicable and we include key parameters for all of Antarctica which may be useful for ice core site selection elsewhere and/or for other purposes.
Supplementary material to "Antarctic climate variability at regional and continental scales over the last 2,000 years"
Publisher: Copernicus GmbH
Date: 22-03-2017
Greenland records of aerosol source and atmospheric lifetime changes from the Eemian to the Holocene
Publisher: Springer Science and Business Media LLC
Date: 16-04-2018
DOI: 10.1038/S41467-018-03924-3
Abstract: The Northern Hemisphere experienced dramatic changes during the last glacial, featuring vast ice sheets and abrupt climate events, while high northern latitudes during the last interglacial (Eemian) were warmer than today. Here we use high-resolution aerosol records from the Greenland NEEM ice core to reconstruct the environmental alterations in aerosol source regions accompanying these changes. Separating source and transport effects, we find strongly reduced terrestrial biogenic emissions during glacial times reflecting net loss of vegetated area in North America. Rapid climate changes during the glacial have little effect on terrestrial biogenic aerosol emissions. A strong increase in terrestrial dust emissions during the coldest intervals indicates higher aridity and dust storm activity in East Asian deserts. Glacial sea salt aerosol emissions in the North Atlantic region increase only moderately (50%), likely due to sea ice expansion. Lower aerosol concentrations in Eemian ice compared to the Holocene are mainly due to shortened atmospheric residence time, while emissions changed little.
Century‐scale perspectives on observed and simulated S outhern O cean sea ice trends from proxy reconstructions
Publisher: American Geophysical Union (AGU)
Date: 10-2016
DOI: 10.1002/2016JC012111
The CoralHydro2k Database: a global, actively curated compilation of coral δ18O and Sr / Ca proxy records of tropical ocean hydrology and temperature for the Common Era
Publisher: Copernicus GmbH
Date: 17-08-2022
Abstract: Abstract. The response of the hydrological cycle to anthropogenic climate change, especially across the tropical oceans, remains poorly understood due to the scarcity of long instrumental temperature and hydrological records. Massive shallow-water corals are ideally suited to reconstructing past oceanic variability as they are widely distributed across the tropics, rapidly deposit calcium carbonate skeletons that continuously record ambient environmental conditions, and can be s led at monthly to annual resolution. Most coral-based reconstructions utilize stable oxygen isotope composition (δ18O) that tracks the combined change in sea surface temperature (SST) and the oxygen isotopic composition of seawater (δ18Osw), a measure of hydrologic variability. Increasingly, coral δ18O time series are paired with time series of strontium-to-calcium ratios (Sr / Ca), a proxy for SST, from the same coral to quantify temperature and δ18Osw variability through time. To increase the utility of such reconstructions, we present the CoralHydro2k database: a compilation of published, peer-reviewed coral Sr / Ca and δ18O records from the Common Era. The database contains 54 paired Sr / Ca-δ18O records and 125 unpaired Sr / Ca or δ18O records, with 88 % of these records providing data coverage from 1800 CE to present. A quality-controlled set of metadata with standardized vocabulary and units accompanies each record, informing the use of the database. The CoralHydro2k database tracks large-scale temperature and hydrological variability. As such, it is well-suited for investigations of past climate variability, comparisons with climate model simulations including isotope-enabled models – and application in paleo-data assimilation projects.The CoralHydro2k database will be available on the NOAA National Center for Environmental Information’s Paleoclimate data service with serializations in MATLAB, R, Python, and LiPD.
Investigating observed northwest Australian rainfall trends in Coupled Model Intercomparison Project phase 5 detection and attribution experiments
Publisher: Wiley
Date: 16-09-2018
DOI: 10.1002/JOC.5788
Climatology of the Mount Brown South ice core site in East Antarctica: implications for the interpretation of a water isotope record
Publisher: Copernicus GmbH
Date: 14-08-2023
Abstract: Abstract. Water stable isotope records from ice cores (δ18O and δD) are a critical tool for constraining long-term temperature variability at high latitudes. However, precipitation in Antarctica consists of semi-continuous small events and intermittent extreme events. In regions of high accumulation, this can bias ice core records towards recording the synoptic climate conditions present during extreme precipitation events. In this study we utilise a combination of ice core data, reanalysis products, and models to understand how precipitation intermittency impacts the temperature records preserved in an ice core from Mount Brown South in East Antarctica. Extreme precipitation events represent only the largest 10 % of all precipitation events, but they account for 52 % of the total annual snowfall at this site, leading to an overrepresentation of these events in the ice core record. Extreme precipitation events are associated with high-pressure systems in the mid-latitudes that cause increased transport of warm and moist air from the southern Indian Ocean to the ice core site. Warm temperatures associated with these events result in a +4.8 ∘C warm bias in the mean annual temperature when weighted by daily precipitation, and water isotopes in the Mount Brown South ice core are shown to be significantly correlated with local temperature when this precipitation-induced temperature bias is included. The Mount Brown South water isotope record spans more than 1000 years and will provide a valuable regional reconstruction of long-term temperature and hydroclimate variability in the data-sparse southern Indian Ocean region.
Climatology of the Mount Brown South ice core site in East Antarctica: implications for the interpretation of a water isotope record
Publisher: Copernicus GmbH
Date: 15-11-2022
DOI: 10.5194/EGUSPHERE-2022-1171
Abstract: Abstract. Water stable isotope records from ice cores (δ18O and δD) are a critical tool for constraining long-term temperature variability in the high-latitudes. However, precipitation in Antarctica consists of semi-continuous small events and intermittent extreme events. In regions of high-accumulation, this can bias ice core records towards recording the synoptic climate conditions present during extreme precipitation events. In this study we utilise a combination of ice core data, re-analysis products and models to understand how precipitation intermittency impacts the temperature records preserved in an ice core from Mount Brown South in East Antarctica. Extreme precipitation events represent only the largest 10 % of all precipitation events, but they account for 44 % of the total annual snowfall at this site leading to an over-representation of these events in the ice core record. Extreme precipitation events are associated with high-pressure systems in the mid-latitudes which cause increased transport of warm and moist air from the southern Indian Ocean to the ice core site. Warm temperatures associated with these events result in a +2.8 °C warm bias in the mean annual temperature when weighted by daily precipitation, and water isotopes in the Mount Brown South ice core are shown to be significantly correlated with local temperature when this precipitation-induced temperature bias is included. The Mount Brown South water isotope record spans more than 1000 years and will provide a valuable regional reconstruction of long-term temperature and hydroclimate variability in the data-sparse southern Indian Ocean region.
Optimal site selection for a high-resolution ice core record in East Antarctica
Publisher: Copernicus GmbH
Date: 08-03-2016
Abstract: Abstract. Ice cores provide some of the best-dated and most comprehensive proxy records, as they yield a vast and growing array of proxy indicators. Selecting a site for ice core drilling is nonetheless challenging, as the assessment of potential new sites needs to consider a variety of factors. Here, we demonstrate a systematic approach to site selection for a new East Antarctic high-resolution ice core record. Specifically, seven criteria are considered: (1) 2000-year-old ice at 300 m depth (2) above 1000 m elevation (3) a minimum accumulation rate of 250 mm years−1 IE (ice equivalent) (4) minimal surface reworking to preserve the deposited climate signal (5) a site with minimal displacement or elevation change in ice at 300 m depth (6) a strong teleconnection to midlatitude climate and (7) an appropriately complementary relationship to the existing Law Dome record (a high-resolution record in East Antarctica). Once assessment of these physical characteristics identified promising regions, logistical considerations (for site access and ice core retrieval) were briefly considered. We use Antarctic surface mass balance syntheses, along with ground-truthing of satellite data by airborne radar surveys to produce all-of-Antarctica maps of surface roughness, age at specified depth, elevation and displacement change, and surface air temperature correlations to pinpoint promising locations. We also use the European Centre for Medium-Range Weather Forecast ERA 20th Century reanalysis (ERA-20C) to ensure that a site complementary to the Law Dome record is selected. We find three promising sites in the Indian Ocean sector of East Antarctica in the coastal zone from Enderby Land to the Ingrid Christensen Coast (50–100° E). Although we focus on East Antarctica for a new ice core site, the methodology is more generally applicable, and we include key parameters for all of Antarctica which may be useful for ice core site selection elsewhere and/or for other purposes.
Supplementary material to "Optimal site selection for a high resolution ice core record in East Antarctica"
Publisher: Copernicus GmbH
Date: 03-11-2015
Related Organisations
British Antarctic Survey
Location: United Kingdom of Great Britain and Northern Ireland
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