ORCID Profile
0000-0002-0728-2712
Current Organisation
Australian Antarctic Division
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Palaeoecology | Magnetism and Palaeomagnetism | Palaeoclimatology | Physical Geography and Environmental Geoscience
Ecosystem Adaptation to Climate Change | Climate Variability (excl. Social Impacts) |
Publisher: American Geophysical Union (AGU)
Date: 08-2016
DOI: 10.1002/2016JC011687
Publisher: Copernicus GmbH
Date: 05-01-2022
Abstract: Abstract. Ice core records from Law Dome in East Antarctica, collected over the the last three decades, provide high resolution data for studies of the climate of Antarctica, Australia and the Southern and Indo-Pacific Oceans. Here we present a set of annually dated records of trace chemistry, stable water isotopes and snow accumulation from Law Dome covering over the period from −11 to 2017 CE (1961 to −66 BP 1950), as well as the level 1 chemistry data from which the annual chemistry records are derived. This dataset provides an update and extensions both forward and back in time of previously published subsets of the data, bringing them together into a coherent set with improved dating. The data are available for download from the Australian Antarctic Data Centre at 0.26179/5zm0-v192.
Publisher: Elsevier BV
Date: 11-2012
Publisher: American Geophysical Union (AGU)
Date: 07-11-2006
DOI: 10.1029/2005JD006764
Publisher: World Scientific Publishing Company
Date: 08-2009
Publisher: Copernicus GmbH
Date: 12-06-2019
DOI: 10.5194/SD-25-1-2019
Abstract: Abstract. A 70 m long continental sediment record was recovered at Darwin Crater in western Tasmania, Australia. The sediment succession includes a pre-lake silty sand deposit overlain by lacustrine silts that have accumulated in the ∼816 ka meteorite impact crater. A total of 160 m of overlapping sediment cores were drilled from three closely spaced holes. Here we report on the drilling operations at Darwin Crater and present the first results from petrophysical whole core logging, lithological core description, and multi-proxy pilot analysis of core end s les. The multi-proxy dataset includes spectrophotometry, grain size, natural gamma rays, paleo- and rock magnetism, loss on ignition, and pollen analyses. The results provide clear signatures of alternating, distinctly different lithologies likely representing glacial and interglacial sediment facies. Initial paleomagnetic analysis indicate normal magnetic polarity in the deepest core at Hole B. If acquired at the time of deposition, this result indicates that the sediment 1 m below commencement of lacustrine deposition post-date the Matuyama–Brunhes geomagnetic reversal ∼773 ka.
Publisher: Elsevier BV
Date: 2013
Publisher: Copernicus GmbH
Date: 23-07-2012
Abstract: Abstract. Antarctic ice cores provide clear evidence of a close coupling between variations in Antarctic temperature and the atmospheric concentration of CO2 during the glacial/interglacial cycles of at least the past 800-thousand years. Precise information on the relative timing of the temperature and CO2 changes can assist in refining our understanding of the physical processes involved in this coupling. Here, we focus on the last deglaciation, 19 000 to 11 000 yr before present, during which CO2 concentrations increased by ~80 parts per million by volume and Antarctic temperature increased by ~10 °C. Utilising a recently developed proxy for regional Antarctic temperature, derived from five near-coastal ice cores and two ice core CO2 records with high dating precision, we show that the increase in CO2 likely lagged the increase in regional Antarctic temperature by less than 400 yr and that even a short lead of CO2 over temperature cannot be excluded. This result, consistent for both CO2 records, implies a faster coupling between temperature and CO2 than previous estimates, which had permitted up to millennial-scale lags.
Publisher: American Geophysical Union (AGU)
Date: 12-03-2016
DOI: 10.1002/2016GL067861
Publisher: American Geophysical Union (AGU)
Date: 15-12-2011
DOI: 10.1029/2011JD016530
Publisher: Copernicus GmbH
Date: 14-07-2022
DOI: 10.5194/EGUSPHERE-2022-574
Abstract: Abstract. During the Mid-Pleistocene Transition (MPT), ca. 1250–800 kya, the Earth’s glacial cycles changed from 41 ky to 100 ky periodicity. The emergence of this longer ice-age periodicity was accompanied by higher global ice volume in glacial periods and lower global ice volume in interglacial periods. Since there is no known change in external orbital forcing across the MPT, it is generally agreed that the cause of this transition is internal to the earth system. Resolving the climate–carbon cycle–cryosphere dynamics processes responsible for the MPT remains a major challenge in ice core and climate science. To address this challenge, the international ice core community has prioritized recovery of an ice core record spanning the MPT interval. The results from such ‘oldest ice’ projects are still several years away. Our objective here it to make an advanced prediction of atmospheric CO2 out to 1.5 my. Our prediction utilizes existing records of atmospheric carbon dioxide (CO2) from Antarctic ice cores spanning the past 800 ky along with the existing benthic water stable isotope (ẟ18O) record from marine sediment cores. Our predictions assume that the relationship between CO2 and benthic ẟ18O over the past 800 thousand years can be extended over the last one and a half million years. The implied null hypothesis is that there has been no fundamental change in the global climate–carbon cycle–cryosphere feedback systems across the MPT. We find that our predicted CO2 record is significantly lower during glacial intervals than the existing blue-ice and boron isotope-based estimates of CO2 that pre-date the continuous 800 ky CO2 record. Our predicted glacial CO2 concentrations are ~9 ppm below glacial CO2 concentrations observed in blue ice data at ca. 1 mya and ~19 ppm below glacial CO2 concentrations reconstructed from boron isotopic data over ca ~1.1–1.25 mya. These results support rejection of our null hypothesis and provide quantitative evidence of a fundamental shift in the global climate–carbon cycle–cryosphere feedback systems across the MPT. However, the definitive test of the various theories explaining the MPT will be comparison of our predicted records with the forthcoming oldest ice core records.
Publisher: Springer Science and Business Media LLC
Date: 09-11-2015
DOI: 10.1038/NGEO2580
Publisher: Springer Science and Business Media LLC
Date: 04-2015
DOI: 10.1038/NATURE14401
Abstract: The last glacial period exhibited abrupt Dansgaard-Oeschger climatic oscillations, evidence of which is preserved in a variety of Northern Hemisphere palaeoclimate archives. Ice cores show that Antarctica cooled during the warm phases of the Greenland Dansgaard-Oeschger cycle and vice versa, suggesting an interhemispheric redistribution of heat through a mechanism called the bipolar seesaw. Variations in the Atlantic meridional overturning circulation (AMOC) strength are thought to have been important, but much uncertainty remains regarding the dynamics and trigger of these abrupt events. Key information is contained in the relative phasing of hemispheric climate variations, yet the large, poorly constrained difference between gas age and ice age and the relatively low resolution of methane records from Antarctic ice cores have so far precluded methane-based synchronization at the required sub-centennial precision. Here we use a recently drilled high-accumulation Antarctic ice core to show that, on average, abrupt Greenland warming leads the corresponding Antarctic cooling onset by 218 ± 92 years (2σ) for Dansgaard-Oeschger events, including the Bølling event Greenland cooling leads the corresponding onset of Antarctic warming by 208 ± 96 years. Our results demonstrate a north-to-south directionality of the abrupt climatic signal, which is propagated to the Southern Hemisphere high latitudes by oceanic rather than atmospheric processes. The similar interpolar phasing of warming and cooling transitions suggests that the transfer time of the climatic signal is independent of the AMOC background state. Our findings confirm a central role for ocean circulation in the bipolar seesaw and provide clear criteria for assessing hypotheses and model simulations of Dansgaard-Oeschger dynamics.
Publisher: Copernicus GmbH
Date: 12-07-2011
Abstract: Abstract. Three near-monthly resolution 10Be records are presented from the Dome Summit South (DSS) ice core site, Law Dome, East Antarctica. The chemical preparation and Accelerator Mass Spectrometer (AMS) measurement of these records is described. The reproducibility of 10Be records at DSS is assessed through intercomparison of the ice core data with data from two previously published and contemporaneous snow pits. We find generally good agreement between the five records, comparable to that observed between other trace chemical records from the site. This result allays concerns raised by a previous Antarctic study (Moraal et al., 2005) about poor reproducibility of ice core 10Be records. A single composite series is constructed from the three ice cores providing a monthly-resolved record of 10Be concentrations at DSS over the past decade (1999 to 2009). To our knowledge, this is the first published ice core data spanning the recent exceptional solar minimum of solar cycle 23. 10Be concentrations are significantly correlated to the cosmic ray flux recorded by the McMurdo neutron monitor (rxy = 0.64, with 95 % CI of 0.53 to 0.71), suggesting that solar modulation of the atmospheric production rate may explain up to ~40 % of the variance in 10Be concentrations at DSS. Sharp concentration peaks occur in most years during the summer-to-autumn, possibly caused by stratospheric incursions. Our results underscore the presence of both production and meteorological signals in ice core 10Be data.
Publisher: Copernicus GmbH
Date: 26-06-2018
Abstract: Abstract. Here, we establish a spatiotemporal evolution of the sea-surface temperatures in the North Atlantic over Dansgaard–Oeschger (DO) events 5–8 (approximately 30–40 kyr) using the proxy surrogate reconstruction method. Proxy data suggest a large variability in North Atlantic sea-surface temperatures during the DO events of the last glacial period. However, proxy data availability is limited and cannot provide a full spatial picture of the oceanic changes. Therefore, we combine fully coupled, general circulation model simulations with planktic foraminifera based sea-surface temperature reconstructions to obtain a broader spatial picture of the ocean state during DO events 5–8. The resulting spatial sea-surface temperature patterns agree over a number of different general circulation models and simulations. We find that sea-surface temperature variability over the DO events is characterized by colder conditions in the subpolar North Atlantic during stadials than during interstadials, and the variability is linked to changes in the Atlantic Meridional Overturning circulation and in the sea-ice cover. Forced simulations are needed to capture the strength of the temperature variability and to reconstruct the variability in other climatic records not directly linked to the sea-surface temperature reconstructions. This is the first time the proxy surrogate reconstruction method has been applied to oceanic variability during MIS3. Our results remain robust, even when age uncertainties of proxy data, the number of available temperature reconstructions, and different climate models are considered. However, we also highlight shortcomings of the methodology that should be addressed in future implementations.
Publisher: American Geophysical Union (AGU)
Date: 27-08-2019
DOI: 10.1029/2019GL084249
Publisher: Copernicus GmbH
Date: 19-07-2022
DOI: 10.5194/ESSD-14-3313-2022
Abstract: Abstract. Ice core records from Law Dome in East Antarctica collected over the last four decades provide high-resolution data for studies of the climate of Antarctica, Australia, and the Southern and Indo-Pacific oceans. Here, we present a set of annually dated records of trace chemistry, stable water isotopes and snow accumulation from Law Dome covering the period from −11 to 2017 CE (1961 to −66 BP 1950) and the level-1 chemistry data from which the annual chemistry records are derived. Law Dome ice core records have been used extensively in studies of the past climate of the Southern Hemisphere and in large-scale data syntheses and reconstructions in a region where few records exist, especially at high temporal resolution. This dataset provides an update and extensions both forward and back in time of previously published subsets of the data, bringing them together into a coherent set with improved dating to enable continued use of this record. The data are available for download from the Australian Antarctic Data Centre at 0.26179/5zm0-v192 (Curran et al., 2021).
Publisher: Elsevier BV
Date: 07-2016
Publisher: Copernicus GmbH
Date: 24-06-2011
Abstract: Abstract. Precise information on the relative timing of north-south climate variations is a key to resolving questions concerning the mechanisms that force and couple climate changes between the hemispheres. We present a new composite record made from five well-resolved Antarctic ice core records that robustly represents the timing of regional Antarctic climate change during the last deglaciation. Using fast variations in global methane gas concentrations as time markers, the Antarctic composite is directly compared to Greenland ice core records, allowing a detailed mapping of the inter-hemispheric sequence of climate changes. Consistent with prior studies the synchronized records show that warming (and cooling) trends in Antarctica closely match cold (and warm) periods in Greenland on millennial timescales. For the first time, we also identify a sub-millennial component to the inter-hemispheric coupling. Within the Antarctic Cold Reversal the strongest Antarctic cooling occurs during the pronounced northern warmth of the Bølling. Warming then resumes in Antarctica, potentially as early as the Intra-Allerød Cold Period, but with dating uncertainty that could place it as late as the onset of the Younger Dryas stadial. There is little-to-no time lag between climate transitions in Greenland and opposing changes in Antarctica. Our results lend support to fast acting inter-hemispheric coupling mechanisms, including recently proposed bipolar atmospheric teleconnections and/or rapid bipolar ocean teleconnections.
Publisher: Copernicus GmbH
Date: 04-03-2021
DOI: 10.5194/EGUSPHERE-EGU21-5890
Abstract: & & Climate data from the sub-Antarctic region are extremely sparse, with few records available beyond the instrumental period. Here, we investigate the suitability of the first-ever ice core collected from Young Island, in the NW Ross Sea, to capture changes in climate. Despite the presence of surface melt at this maritime location, our findings indicate that stable water isotope and trace element records can still hold potential for paleoclimate reconstruction. We apply two multi-proxy dating approaches based on winter and summer signatures, develop an ice core chronology, and contextualize our findings using a local automatic weather station and reanalysis data. Subsequently, we draw first conclusions about the surface conditions at Young Island and discuss the site& #8217 s potential for future studies aimed at paleoclimate reconstruction and resolving the effects of surface melt on proxy records.& &
Publisher: Springer Science and Business Media LLC
Date: 08-04-2021
DOI: 10.1038/S41467-021-22241-W
Abstract: Data availability and temporal resolution make it challenging to unravel the anatomy (duration and temporal phasing) of the Last Glacial abrupt climate changes. Here, we address these limitations by investigating the anatomy of abrupt changes using sub-decadal-scale records from Greenland ice cores. We highlight the absence of a systematic pattern in the anatomy of abrupt changes as recorded in different ice parameters. This ersity in the sequence of changes seen in ice-core data is also observed in climate parameters derived from numerical simulations which exhibit self-sustained abrupt variability arising from internal atmosphere-ice-ocean interactions. Our analysis of two ice cores shows that the ersity of abrupt warming transitions represents variability inherent to the climate system and not archive-specific noise. Our results hint that during these abrupt events, it may not be possible to infer statistically-robust leads and lags between the different components of the climate system because of their tight coupling.
Publisher: Springer Science and Business Media LLC
Date: 12-12-2017
DOI: 10.1038/NGEO2848
Publisher: Elsevier BV
Date: 12-2014
Publisher: Copernicus GmbH
Date: 27-03-2022
DOI: 10.5194/EGUSPHERE-EGU22-5683
Abstract: & & Over the last four decades, the Southern Ocean has been characterized by now-persistent stronger westerly winds, with consequences for the Antarctic region climate, including variations in sea ice extent and primary productivity. Here we present the first ever bromine, sodium and iodine records, tracers of sea salt aerosols, sea ice and primary productivity, from five sub-Antarctic ice cores, retrieved from Bouvet, Young, Peter I and Mount Siple Island and Mertz glacier. The aim of the study is (1) to assess if halogens deposited in sub-Antarctic regions are influenced by recent changes in wind forcing and (2) to better understand the underlying processes of halogens emission from ocean/sea ice, their transport and deposition over the Antarctic region.& & & & The trends of sodium and bromine, emitted and transported with sea salt aerosols, suggest that wind strengthening leads to more halogens deposited in the sub-Antarctic. Also, we find that bromine is depleted with respect to the bromine-to-sodium sea-water ratio at all sites, indicating that bromine species are sustained in the marine boundary layer by halogen chemistry and are less prone to be deposited. Iodine records show a positive correlation with marginal sea ice and primary productivity variability, suggesting that iodine species emitted at the edge are deposited more efficiently than bromine species.& &
Publisher: Copernicus GmbH
Date: 23-08-2017
Publisher: Elsevier BV
Date: 08-2015
Publisher: Elsevier BV
Date: 07-2018
Publisher: Elsevier BV
Date: 2018
Publisher: Copernicus GmbH
Date: 08-06-2023
DOI: 10.5194/EGUSPHERE-2023-1064
Abstract: Abstract. Peter 1st Island is situated in the Bellingshausen Sea, a region that has experienced considerable climate change in recent decades. Warming sea surface temperatures and reduced sea ice cover have been accompanied by warming surface air temperature, increased snowfall, and accelerated mass loss over the adjacent ice sheet. Here we present data from the first firn core drilled on Peter 1st Island, spanning the period 2001–2017 CE. The stable water isotope data capture regional changes in surface air temperature, and precipitation (snow accumulation) at the site, which are highly correlated with the surrounding Amundsen-Bellingshausen Seas, and the adjacent Antarctic Peninsula (r .6, p .05). The unique in-situ data from an automatic weather station, together with the firn core data, confirms the high skill of the ERA5 reanalysis in capturing daily mean temperature and inter-annual precipitation variability, even over a small Sub-Antarctic Island. This study demonstrates the suitability of Peter 1st Island for future deep ice core drilling, with the potential to provide an invaluable archive to explore ice-ocean-atmosphere interactions over decadal to centennial timescales for this dynamic region.
Publisher: Copernicus GmbH
Date: 23-08-2017
DOI: 10.5194/CP-2017-96
Abstract: Abstract. Here we present a revised Law Dome, Dome Summit South (DSS) ice core age model (denoted LD2017) that significantly improves the chronology over the last 88 ka. An ensemble approach was used, allowing for the computation of both a median age and associated uncertainty as a function of depth. The revised chronology incorporates extended continuous annual layer counting to 853 m using chemical species with seasonally-varying behaviours. The annual layer counted age at 853 m is 2332 years before 2000 (y b2k) with an error of & lus /−7 y, i.e. 2345–2325 y b2k . Below this depth, non-linear interpolation between age ties using a probability density function for age/depth is used to constrain and model the age of the ice. The ice-based age ties below the annual layer counted section are based on matching volcanic event markers, methane (CH4) gas concentration, isotopic composition of ice (δ18O) and the Last Glacial Maximum (LGM) dust peak to other records. For consistency, the timescale used for all matching is the AICC2012 timescale (Veres et al., 2013). The first ice-based age tie is the base of the annual layer counting record (2332 y b2k) and the age ties from ~ 2400–4000 y b2k are volcanic synchronised ice-based age ties. The detection of abrupt changes in CH4 gas concentrations within the DSS record provides further independent gas-based age ties, including the tightly constrained 8200 y b2k event. The improved age control between 9000 and 21000 y b2k is supplemented by CH4 and δ18O ice measurements (Pedro et al., 2011). Over the period 16600 to 18600 y b2k large changes in dust concentration, matched to the EDC dust record, are used to constrain two ice-based age ties. Unlike previous studies, where the modelling was used to simultaneously infer both age and snow accumulation rate, we made an independent estimate of the snow accumulation rate, where required, for the use of gas based age ties.
Publisher: Copernicus GmbH
Date: 24-06-2020
DOI: 10.5194/TC-2020-110
Abstract: Abstract. The sub-Antarctic is one of the most data sparse regions on earth. A number of glaciated Antarctic and sub-Antarctic islands have the potential to provide unique ice core records of past climate, atmospheric circulation and sea ice. However, very little is known about the glaciology of these remote islands or their vulnerability to warming atmospheric temperatures. Here we present ground penetrating radar (GPR), melt histories and density profiles from shallow ice cores (14 to 24 m) drilled on three sub-Antarctic islands and two Antarctic coastal domes. This includes the first ever ice cores from Bouvet Island (54°26’0 S, 3°25’0 E) in the South Atlantic, from Peter 1st Island (68°50’0 S, 90°35’0 W) in the Bellingshausen Sea and from Young Island (66°17′ S, 162°25′ E) in the Ross Sea sector’s Balleny Islands chain. Despite their sub-Antarctic location, surface melt is low at most sites (melt layers account for ∼10 % of total core), with undisturbed ice layers in the upper ∼40 m, suggesting minimal impact of melt water percolation. The exception is Young Island, where melt layers account for 47 % of the ice core. Surface snow densities range from 0.47 to 0.52 kg m3, with close-off depths ranging from 21 to 51 m. Based on the measured density, we estimate that the bottom ages of a 100 m ice core drilled on Peter 1st Island would reach ~1836 AD and ~1743 AD at Young Island.
Publisher: Copernicus GmbH
Date: 03-03-2021
DOI: 10.5194/EGUSPHERE-EGU21-1556
Abstract: & & We use a LGM setup of the CESM with marine and terrestrial biogeochemistry. This free-running& set-up (i.e., no freshwater hosing) exhibts Dansgaard-Oeschger events and Antarctic Isotope Maxima with time-lags and litudes that are consistent with paleo reconstructions. The CO2 signal associated DO events is also consistent with reconstructions: a 10 ppm/kyr increase during stadials, with the increase continuing some 400 years after Antarctica has started to cool again. An analysis of the modelled air-sea/land carbon fluxes reveals that some 3ppm of the stadial increase are due to shifting rain and temperature patterns that reduce growth of land vegetation. This adjustment is largely concluded after 3 centuries. The remainder of the signal is due to reduced ocean uptake. It turns out that reduced subduction of carbon in the Southern Ocean is mostly compensated by reduced upwelling in the equatorial oceans. Thus, as found in previous studies, much of the extra carbon is due to reduced uptake in the North Atlantic, partly directly due to reduced deep convection, and partly due to a reduced biological productivity because much of the North Atlantic nutrients are supplied by the AMOC. A big surprise is the emergence of the North Pacific as a major contributor to the changes in the air-fluxes of carbon. It is the reorganization of its wind-driven circulation that explains why global net-outgassing of carbon continues long after the interstadial has begun.& &
Publisher: Copernicus GmbH
Date: 03-03-2021
Abstract: Abstract. The sub-Antarctic is one of the most data-sparse regions on earth. A number of glaciated Antarctic and sub-Antarctic islands have the potential to provide unique ice core records of past climate, atmospheric circulation, and sea ice. However, very little is known about the glaciology of these remote islands or their vulnerability to warming atmospheric temperature. Here we present melt histories and density profiles from shallow ice (firn) cores (14 to 24 m) drilled on three sub-Antarctic islands and two Antarctic coastal domes. Additionally, complementary ground-penetrating radar (GPR) data were collected to further characterize each site and assess the spatial distribution of the observed melt layers. This study includes the first ever firn cores from Bouvet Island (54∘25′19′′ S, 03∘23′27′′ E) in the South Atlantic, from Peter I Island (68∘51′05′′ S, 90∘30′35′′ W) in the Bellingshausen Sea, and from Young Island (66∘31′44′′ S, 162∘33′21′′ E) in the Ross Sea sector's Balleny island chain. Despite their sub-Antarctic location, surface melt is low at most sites (melt layers account for ∼ 10 % of total core), with undisturbed ice layers in the upper ∼ 40 m, suggesting minimal impact of meltwater percolation. The exception is Young Island, where melt layers account for 47 % of the firn core. Surface snow densities range from 0.47 to 0.52 kg m−3, with close-off depths ranging from 21 to 51 m. Based on the measured density, we estimate that the bottom ages of a 100 m ice core drilled on Peter 1 Island would reach ∼ 1856 CE and ∼ 1874 CE at Young Island.
Start Date: 2018
End Date: 2021
Funder: Marsden Fund
View Funded ActivityStart Date: 09-2017
End Date: 09-2020
Amount: $355,000.00
Funder: Australian Research Council
View Funded Activity