ORCID Profile
0000-0002-2048-0019
Current Organisation
Durham University
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Physical Oceanography | Glaciology | Climate Change Processes | Oceanography
Effects of Climate Change and Variability on Antarctic and Sub-Antarctic Environments (excl. Social Impacts) | Expanding Knowledge in the Environmental Sciences | Expanding Knowledge in the Earth Sciences |
Publisher: Geological Society of America
Date: 09-2006
DOI: 10.1130/B25735.1
Publisher: Elsevier BV
Date: 05-2019
Publisher: Copernicus GmbH
Date: 15-03-2023
Abstract: Abstract. Nioghalvfjerdsbrae, or 79∘ N Glacier, is the largest marine-terminating glacier draining the Northeast Greenland Ice Stream (NEGIS). In recent years, its ∼ 70 km long fringing ice shelf (hereafter referred to as the 79∘ N ice shelf) has thinned, and a number of small calving events highlight its sensitivity to climate warming. With the continued retreat of the 79∘ N ice shelf and the potential for accelerated discharge from NEGIS, which drains 16 % of the Greenland Ice Sheet (GrIS), it has become increasingly important to understand the long-term history of the ice shelf in order to put the recent changes into perspective and to judge their long-term significance. Here, we reconstruct the Holocene dynamics of the 79∘ N ice shelf by combining radiocarbon dating of marine molluscs from isostatically uplifted glaciomarine sediments with a multi-proxy investigation of two sediment cores recovered from Blåsø, a large epishelf lake 2–13 km from the current grounding line of 79∘ N Glacier. Our reconstructions suggest that the ice shelf retreated between 8.5 and 4.4 ka cal BP, which is consistent with previous work charting grounding line and ice shelf retreat to the coast as well as open marine conditions in Nioghalvfjerdsbrae. Ice shelf retreat followed a period of enhanced atmospheric and ocean warming in the Early Holocene. Based on our detailed sedimentological, microfaunal, and biomarker evidence, the ice shelf reformed at Blåsø after 4.4 ka cal BP, reaching a thickness similar to present by 4.0 ka cal BP. Reformation of the ice shelf coincides with decreasing atmospheric temperatures, the increased dominance of Polar Water, a reduction in Atlantic Water, and (near-)perennial sea-ice cover on the adjacent continental shelf. Along with available climate archives, our data indicate that the 79∘ N ice shelf is susceptible to collapse at mean atmospheric and ocean temperatures ∼ 2 ∘C warmer than present, which could be achieved by the middle of this century under some emission scenarios. Finally, the presence of “marine” markers in the uppermost part of the Blåsø sediment cores could record modern ice shelf thinning, although the significance and precise timing of these changes requires further work.
Publisher: Geological Society of America
Date: 2004
DOI: 10.1130/G19795.1
Publisher: Geological Society of America
Date: 05-2010
DOI: 10.1130/G30754.1
Publisher: Elsevier BV
Date: 10-2007
Publisher: Copernicus GmbH
Date: 02-03-2022
Abstract: Abstract. Antarctic sea ice is a critical component of the climate system affecting a range of physical and biogeochemical feedbacks and supporting unique ecosystems. During the last glacial stage, Antarctic sea ice was more extensive than today, but uncertainties in geological (marine sediments), glaciological (ice core), and climate model reconstructions of past sea-ice extent continue to limit our understanding of its role in the Earth system. Here, we present a novel archive of past sea-ice environments from regurgitated stomach oils of snow petrels (Pagodroma nivea) preserved at nesting sites in Dronning Maud Land, Antarctica. We show that by combining information from fatty acid distributions and their stable carbon isotope ratios with measurements of bulk carbon and nitrogen stable isotopes and trace metal data, it is possible to reconstruct changing snow petrel diet within Marine Isotope Stage 2 (ca. 24.3–30.3 cal kyr BP). We show that, as today, a mixed diet of krill and fish characterizes much of the record. However, between 27.4 and 28.7 cal kyr BP signals of krill almost disappear. By linking dietary signals in the stomach-oil deposits to modern feeding habits and foraging ranges, we infer the use by snow petrels of open-water habitats (“polynyas”) in the sea ice during our interval of study. The periods when consumption of krill was reduced are interpreted to correspond to the opening of polynyas over the continental shelf, which became the preferred foraging habitat. Our results show that extensive, thick, and multiyear sea ice was not always present close to the continent during the last glacial stage and highlight the potential of stomach-oil deposits as a palaeoenvironmental archive of Southern Ocean conditions.
Publisher: Informa UK Limited
Date: 06-2005
Publisher: American Geophysical Union (AGU)
Date: 11-2011
DOI: 10.1029/2011GL049277
Publisher: American Geophysical Union (AGU)
Date: 17-02-2022
DOI: 10.1029/2021GL097109
Abstract: In Antarctica, Global Positioning System (GPS) vertical time series exhibit non‐linear signals over a wide range of temporal scales. To explain these non‐linearities, a number of hypotheses have been proposed, among them the short‐term rapid solid Earth response to contemporaneous ice mass change. Here we use GPS vertical time series to reveal the solid Earth response to variations in surface mass balance (SMB) in the Southern Antarctic Peninsula (SAP). At four locations in the SAP we show that interannual variations of SMB anomalies cause measurable elastic deformation. We use regional climate model SMB products to calculate the induced displacement assuming a perfectly elastic Earth. Our results show a reduction of the misfit when fitting a linear trend to GPS time series corrected for the elastic response to SMB variations. Our results imply that, for a better understanding of the glacial isostatic adjustment signal in Antarctica, SMB variability must be considered.
Publisher: Oxford University Press (OUP)
Date: 27-06-2012
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.
Publisher: Elsevier BV
Date: 03-2015
Publisher: Elsevier BV
Date: 10-2016
Publisher: Copernicus GmbH
Date: 21-09-2022
DOI: 10.5194/TC-2022-173
Abstract: Abstract. Nioghalvfjerdsbrae, or 79° N Glacier, is the largest marine-terminating glacier draining Northeast Greenland Ice Stream (NEGIS). In recent years, it’s ~70 km-long fringing ice shelf (hereafter referred to as 79° N ice shelf) has thinned, and a number of small calving events highlight its sensitivity to climate warming. With the continued retreat of 79° N ice shelf and the potential for accelerated discharge from NEGIS, which drains 16 % of the Greenland Ice Sheet (GrIS), it has become increasingly important to understand the long-term history of the ice shelf in order to put the recent changes into perspective and to judge their long-term significance. Here we reconstruct the Holocene dynamics of 79° N ice shelf by combining radiocarbon dating of marine mollusc from isostatically uplifted glacimarine sediments with a multi-proxy investigation of two sediment cores recovered from Blåsø, a large epishelf lake 2–13 km from the current grounding line of 79° N Glacier. Our reconstructions suggest that the ice shelf retreated between 8.5 and 4.4 cal. ka. BP, which is consistent with previous work charting grounding line and ice shelf retreat to the coast, and open marine conditions in Nioghalvfjerdsbrae. Ice shelf retreat followed a period of enhanced atmospheric and ocean warming in the Early Holocene. Based on our detailed sedimentological, microfaunal and biomarker evidence the ice shelf reformed at Blåsø after 4.4 cal. ka BP, reaching a thickness similar to present by 4.0 cal. ka BP. Reformation of the ice shelf coincides with decreasing atmospheric temperatures, increased dominance of Polar Water, a reduction in Atlantic Water and (near) perennial sea-ice cover on the adjacent continental shelf. Together with available climate archives our data indicate that 79° N ice shelf is susceptible to collapse when mean atmospheric and ocean temperatures are ~2 °C warmer than present, which could be achieved by the middle of this century under some climate model scenarios. Finally, the presence of ‘marine’ markers in the uppermost part of the Blåsø sediment cores could record modern ice shelf thinning, although the significance and precise timing of these changes requires further work.
Publisher: Elsevier BV
Date: 09-2014
Publisher: Copernicus GmbH
Date: 04-10-2021
DOI: 10.5194/CP-2021-134
Abstract: Abstract. Antarctic sea ice is a critical component of the climate system, affecting a range of physical and biogeochemical feedbacks, and supporting unique ecosystems. During the last glacial stage, Antarctic sea ice was more extensive than today, but uncertainties in geological (marine sediments), glaciological (ice core), and climate model reconstructions of past sea-ice extent continue to limit our understanding of its role in the Earth system. Here, we present a novel archive of past sea-ice environments from regurgitated stomach oils of snow petrels (Pagodroma nivea), preserved at nesting sites in Dronning Maud Land, Antarctica. We show that by combining information from fatty acid distributions and their stable carbon isotope ratios with measurements of bulk carbon and nitrogen stable isotopes and trace metal data, it is possible to reconstruct changing snow petrel diet within Marine Isotope Stage 2 (ca. 22.6–28.8 cal. kyr BP). We show that, as today, a mixed diet of krill and fish characterises much of the record. However, between 25.7–26.8 cal. kyr BP signals of krill almost disappear. By linking dietary signals in the stomach-oil deposits to modern feeding habits and foraging ranges, we infer the use by snow petrels of open water habitats (‘polynyas’) in the sea ice during our interval of study. The periods when consumption of krill was reduced are interpreted to correspond to the opening of polynyas over the continental shelf, which became the preferred foraging habitat. Our results challenge hypotheses that the development of extensive, thick, multi-year sea-ice close to the continent was a key driver of positive sea ice-climate feedbacks during glacial stages, and highlight the potential of stomach-oil deposits as a palaeo-environmental archive of Southern Ocean conditions.
Publisher: Elsevier BV
Date: 09-2014
Publisher: Elsevier BV
Date: 04-2019
Publisher: Elsevier BV
Date: 12-2019
Publisher: American Geophysical Union
Date: 2011
DOI: 10.1029/2010GM000940
Publisher: Geological Society of America
Date: 05-2011
DOI: 10.1130/G32140Y.1
Publisher: Informa UK Limited
Date: 06-2005
Publisher: Springer Science and Business Media LLC
Date: 21-10-2012
DOI: 10.1038/NATURE11621
Abstract: Recent estimates of Antarctica's present-day rate of ice-mass contribution to changes in sea level range from 31 gigatonnes a year (Gt yr(-1) ref. 1) to 246 Gt yr(-1) (ref. 2), a range that cannot be reconciled within formal errors. Time-varying rates of mass loss contribute to this, but substantial technique-specific systematic errors also exist. In particular, estimates of secular ice-mass change derived from Gravity Recovery and Climate Experiment (GRACE) satellite data are dominated by significant uncertainty in the accuracy of models of mass change due to glacial isostatic adjustment (GIA). Here we adopt a new model of GIA, developed from geological constraints, which produces GIA rates systematically lower than those of previous models, and an improved fit to independent uplift data. After applying the model to 99 months (from August 2002 to December 2010) of GRACE data, we estimate a continent-wide ice-mass change of -69 ± 18 Gt yr(-1) (+0.19 ± 0.05 mm yr(-1) sea-level equivalent). This is about a third to a half of the most recently published GRACE estimates, which cover a similar time period but are based on older GIA models. Plausible GIA model uncertainties, and errors relating to removing longitudinal GRACE artefacts ('destriping'), confine our estimate to the range -126 Gt yr(-1) to -29 Gt yr(-1) (0.08-0.35 mm yr(-1) sea-level equivalent). We resolve 26 independent drainage basins and find that Antarctic mass loss, and its acceleration, is concentrated in basins along the Amundsen Sea coast. Outside this region, we find that West Antarctica is nearly in balance and that East Antarctica is gaining substantial mass.
Publisher: American Geophysical Union (AGU)
Date: 12-09-2012
DOI: 10.1029/2012GL052559
Publisher: Elsevier BV
Date: 02-2019
Publisher: Elsevier BV
Date: 09-2011
Publisher: Elsevier BV
Date: 09-2014
Publisher: Elsevier BV
Date: 06-2012
Publisher: Springer Science and Business Media LLC
Date: 11-2006
Publisher: Elsevier BV
Date: 03-2007
Publisher: American Association for the Advancement of Science (AAAS)
Date: 30-11-2012
Abstract: Mass loss from the ice sheets of Greenland and Antarctica account for a large fraction of global sea-level rise. Part of this loss is because of the effects of warmer air temperatures, and another because of the rising ocean temperatures to which they are being exposed. Joughin et al. (p. 1172 ) review how ocean-ice interactions are impacting ice sheets and discuss the possible ways that exposure of floating ice shelves and grounded ice margins are subject to the influences of warming ocean currents. Estimates of the mass balance of the ice sheets of Greenland and Antarctica have differed greatly—in some cases, not even agreeing about whether there is a net loss or a net gain—making it more difficult to project accurately future sea-level change. Shepherd et al. (p. 1183 ) combined data sets produced by satellite altimetry, interferometry, and gravimetry to construct a more robust ice-sheet mass balance for the period between 1992 and 2011. All major regions of the two ice sheets appear to be losing mass, except for East Antarctica. All told, mass loss from the polar ice sheets is contributing about 0.6 millimeters per year (roughly 20% of the total) to the current rate of global sea-level rise.
Location: United Kingdom of Great Britain and Northern Ireland
Location: United Kingdom of Great Britain and Northern Ireland
Start Date: 08-2021
End Date: 12-2027
Amount: $20,000,000.00
Funder: Australian Research Council
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