The Experts below are selected from a list of 189 Experts worldwide ranked by ideXlab platform
Julian A. Dowdeswell - One of the best experts on this subject based on the ideXlab platform.
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paleoenvironments during younger dryas early holocene retreat of the greenland Ice sheet from outer disko trough central west greenland
Journal of Quaternary Science, 2014Co-Authors: Anne E Jennings, John T Andrews, Colm Ó Cofaigh, Mariah Walton, A A Kilfeather, Joseph D Ortiz, Anne De Vernal, Julian A. DowdeswellAbstract:Paleoenvironments during the late Younger Dryas through early Holocene retreat of the Greenland Ice Sheet from the outer shelf in the Disko Trough system of central West Greenland were investigated via lithofacies, foraminifera, dinocysts and sediment provenance analyses in radiocarbon-dated sediment cores from the upper slope (JR175-VC35) and outer shelf (JR175-VC20 and HU2008029-070CC). Core data show that the Ice margin retreated rapidly from the outer shelf by calving, beginning by 12.2k cal a BP under cold paleoceano- graphic conditions with up to 11 months of sea-Ice. Ice retreat into Disko Bugt was well underway by 10.9k cal a BP. Enhanced Ice-sheet ablation in Disko Bugt and elsewhere along the West Greenland coast is inferred from cold glacial marine conditions associated with high sedimentation rates between 10.9 and 9.5k cal a BP on the outer shelf. Glacial marine conditions are recorded on the outer shelf until 7.8k cal a BP. Detrital carbonate-bearing sediments rich in >2-mm clasts deposited between 11.6 and 10.6k cal a BP indicate that Icebergs calved from northern Baffin Bay Ice margins were melting and releasing sediments along West Greenland while the Greenland Ice Sheet margin was retreating into Disko Bugt. Copyright # 2013 John Wiley & Sons, Ltd.
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Paleoenvironments during Younger Dryas‐Early Holocene retreat of the Greenland Ice Sheet from outer Disko Trough, central west Greenland
Journal of Quaternary Science, 2013Co-Authors: Anne E Jennings, John T Andrews, Colm Ó Cofaigh, A A Kilfeather, Joseph D Ortiz, Anne De Vernal, Mariah E. Walton, Julian A. DowdeswellAbstract:Paleoenvironments during the late Younger Dryas through early Holocene retreat of the Greenland Ice Sheet from the outer shelf in the Disko Trough system of central West Greenland were investigated via lithofacies, foraminifera, dinocysts and sediment provenance analyses in radiocarbon-dated sediment cores from the upper slope (JR175-VC35) and outer shelf (JR175-VC20 and HU2008029-070CC). Core data show that the Ice margin retreated rapidly from the outer shelf by calving, beginning by 12.2k cal a BP under cold paleoceano- graphic conditions with up to 11 months of sea-Ice. Ice retreat into Disko Bugt was well underway by 10.9k cal a BP. Enhanced Ice-sheet ablation in Disko Bugt and elsewhere along the West Greenland coast is inferred from cold glacial marine conditions associated with high sedimentation rates between 10.9 and 9.5k cal a BP on the outer shelf. Glacial marine conditions are recorded on the outer shelf until 7.8k cal a BP. Detrital carbonate-bearing sediments rich in >2-mm clasts deposited between 11.6 and 10.6k cal a BP indicate that Icebergs calved from northern Baffin Bay Ice margins were melting and releasing sediments along West Greenland while the Greenland Ice Sheet margin was retreating into Disko Bugt. Copyright # 2013 John Wiley & Sons, Ltd.
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Ice-stream stability on a reverse bed slope
Nature Geoscience, 2012Co-Authors: Stewart S. R. Jamieson, Andreas Vieli, Stephen J. Livingstone, Colm Ó Cofaigh, Chris R. Stokes, Claus-dieter Hillenbrand, Julian A. DowdeswellAbstract:Marine Ice streams whose beds deepen inland are thought to be inherently unstable. Numerical modelling of the Maguerite Bay Ice-stream retreat in West Antarctica since the Last Glacial Maximum suggests that an Ice stream can stabilize on an inland-sloping bed owing to increased lateral drag where the Ice stream narrows. Marine-based Ice streams whose beds deepen inland are thought to be inherently unstable1,2,3. This instability is of particular concern because significant portions of the marine-based West Antarctic and Greenland Ice sheets are losing mass and their retreat could contribute significantly to future sea-level rise4,5,6,7. However, the present understanding of Ice-stream stability is limited by observational records that are too short to resolve multi-decadal to millennial-scale behaviour or to validate numerical models8. Here we present a dynamic numerical simulation of Antarctic Ice-stream retreat since the Last Glacial Maximum (LGM), constrained by geophysical data, whose behaviour is consistent with the geomorphological record. We find that retreat of Marguerite Bay Ice Stream following the LGM was highly nonlinear and was interrupted by stabilizations on a reverse-sloping bed, where theory predicts rapid unstable retreat. We demonstrate that these transient stabilizations were caused by enhanced lateral drag as the Ice stream narrowed. We conclude that, as well as bed topography, Ice-stream width and long-term retreat history are crucial for understanding decadal- to centennial-scale Ice-stream behaviour and marine Ice-sheet vulnerability.
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Ice stream grounding-line stability on a reverse bed slope
2012Co-Authors: Stewart S. R. Jamieson, Andreas Vieli, Stephen J. Livingstone, Colm Ó Cofaigh, Chris R. Stokes, Claus-dieter Hillenbrand, Julian A. DowdeswellAbstract:Marine-based Ice streams whose beds deepen inland are thought to be inherently unstable1, 2, 3. This instability is of particular concern because significant portions of the marine-based West Antarctic and Greenland Ice sheets are losing mass and their retreat could contribute significantly to future sea-level rise4, 5, 6, 7. However, the present understanding of Ice-stream stability is limited by observational records that are too short to resolve multi-decadal to millennial-scale behaviour or to validate numerical models8. Here we present a dynamic numerical simulation of Antarctic Ice-stream retreat since the Last Glacial Maximum (LGM), constrained by geophysical data, whose behaviour is consistent with the geomorphological record. We find that retreat of Marguerite Bay Ice Stream following the LGM was highly nonlinear and was interrupted by stabilizations on a reverse-sloping bed, where theory predicts rapid unstable retreat. We demonstrate that these transient stabilizations were caused by enhanced lateral drag as the Ice stream narrowed. We conclude that, as well as bed topography, Ice-stream width and long-term retreat history are crucial for understanding decadal- to centennial-scale Ice-stream behaviour and marine Ice-sheet vulnerability.
Ruza F. Ivanovic - One of the best experts on this subject based on the ideXlab platform.
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Simulating the Early Holocene demise of the Laurentide Ice Sheet with BISICLES (public trunk revision 3298)
Geoscientific Model Development, 2020Co-Authors: Ilkka S. O. Matero, Lauren J. Gregoire, Ruza F. IvanovicAbstract:Abstract. Simulating the demise of the Laurentide Ice Sheet covering Hudson Bay in the Early Holocene (10–7 ka) is important for understanding the role of accelerated changes in Ice sheet topography and melt in the 8.2 ka event, a century long cooling of the Northern Hemisphere by several degrees. Freshwater released from the Ice sheet through a surface mass balance instability (known as the saddle collapse) has been suggested as a major forcing for the 8.2 ka event, but the temporal evolution of this pulse has not been constrained. Dynamical Ice loss and marine interactions could have significantly accelerated the Ice sheet demise, but simulating such processes requires computationally expensive models that are difficult to configure and are often impractical for simulating past Ice sheets. Here, we developed an Ice sheet model setup for studying the Laurentide Ice Sheet's Hudson Bay saddle collapse and the associated meltwater pulse in unprecedented detail using the BISICLES Ice sheet model, an efficient marine Ice sheet model of the latest generation which is capable of refinement to kilometre-scale resolutions and higher-order Ice flow physics. The setup draws on previous efforts to model the deglaciation of the North American Ice Sheet for initialising the Ice sheet temperature, recent Ice sheet reconstructions for developing the topography of the region and Ice sheet, and output from a general circulation model for a representation of the climatic forcing. The modelled deglaciation is in agreement with the reconstructed extent of the Ice sheet, and the associated meltwater pulse has realistic timing. Furthermore, the peak magnitude of the modelled meltwater equivalent (0.07–0.13 Sv) is compatible with geological estimates of freshwater discharge through the Hudson Strait. The results demonstrate that while improved representations of the glacial dynamics and marine interactions are key for correctly simulating the pattern of Early Holocene Ice sheet retreat, surface mass balance introduces by far the most uncertainty. The new model configuration presented here provides future opportunities to quantify the range of plausible amplitudes and durations of a Hudson Bay Ice saddle collapse meltwater pulse and its role in forcing the 8.2 ka event.
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Simulating the Early Holocene demise of the Laurentide Ice Sheet with BISICLES (public trunk revision 3298)
2019Co-Authors: Ilkka Matero, Lauren J. Gregoire, Ruza F. IvanovicAbstract:Abstract. Simulating the demise of the Laurentide Ice Sheet covering the Hudson Bay in the early Holocene (10-7 ka) is important for understanding the role of accelerated changes in Ice sheet topography and melt in the 8.2 ka event , a century long cooling of the Northern Hemisphere by several degrees. Freshwater released from the Ice sheet through a surface mass balance instability (known as the saddle collapse) has been suggested as a major forcing for the 8.2 ka event, but the temporal evolution of this pulse has not been constrained. Dynamical Ice loss and marine interactions could have significantly accelerated the Ice sheet demise, but simulating such processes requires computationally expensive models that are difficult to configure and are often impractical for simulating past Ice sheets. Here, we developed an Ice sheet model setup for studying the Laurentide Ice Sheet’s Hudson Bay saddle collapse and the associated meltwater pulse in unprecedented detail using the BISICLES Ice sheet model, an efficient marine Ice sheet model of the latest generation, capable of refinement to kilometre-scale resolution and higher-order Ice flow physics. The setup draws on previous efforts to model the deglaciation of the North American Ice Sheet for initialising the Ice sheet temperature, recent Ice sheet reconstructions for developing the topography of the region and Ice sheet, and output from a general circulation model for a representation of the climatic forcing. The modelled deglaciation is in agreement with the reconstructed extent of the Ice sheet and the associated meltwater pulse has realistic timing. Furthermore,the peak magnitude of the modelled meltwater equivalent (0.07–0.13 Sv) is compatible with geological estimates of freshwater discharge through the Hudson Strait. The results demonstrate that while improved representation of the glacial dynamics and marine interactions are key for correctly simulating the pattern of early Holocene Ice sheet retreat, surface mass balance introduces by far the most uncertainty. The new model configuration presented here provides future opportunities to quantify the range of plausible amplitudes and durations of a Hudson Bay Ice saddle collapse meltwater pulse and its role in forcing the 8.2 ka event.
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The 8.2 ka cooling event caused by Laurentide Ice saddle collapse
Earth and Planetary Science Letters, 2017Co-Authors: Ilkka Matero, Lauren J. Gregoire, Ruza F. Ivanovic, Julia C. Tindall, Alan M. HaywoodAbstract:Abstract The 8.2 ka event was a period of abrupt cooling of 1–3 °C across large parts of the Northern Hemisphere, which lasted for about 160 yr. The original hypothesis for the cause of this event has been the outburst of the proglacial Lakes Agassiz and Ojibway. These drained into the Labrador Sea in ∼0.5–5 yr and slowed the Atlantic Meridional Overturning Circulation, thus cooling the North Atlantic region. However, climate models have not been able to reproduce the duration and magnitude of the cooling with this forcing without including additional centennial-length freshwater forcings, such as rerouting of continental runoff and Ice sheet melt in combination with the lake release. Here, we show that instead of being caused by the lake outburst, the event could have been caused by accelerated melt from the collapsing Ice saddle that linked domes over Hudson Bay in North America. We forced a General Circulation Model with time varying meltwater pulses (100–300 yr) that match observed sea level change, designed to represent the Hudson Bay Ice saddle collapse. A 100 yr long pulse with a peak of 0.6 Sv produces a cooling in central Greenland that matches the 160 yr duration and 3 °C amplitude of the event recorded in Ice cores. The simulation also reproduces the cooling pattern, amplitude and duration recorded in European Lake and North Atlantic sediment records. Such abrupt acceleration in Ice melt would have been caused by surface melt feedbacks and marine Ice sheet instability. These new realistic forcing scenarios provide a means to reconcile longstanding mismatches between proxy data and models, allowing for a better understanding of both the sensitivity of the climate models and processes and feedbacks in motion during the disintegration of continental Ice sheets.
John T Andrews - One of the best experts on this subject based on the ideXlab platform.
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paleoenvironments during younger dryas early holocene retreat of the greenland Ice sheet from outer disko trough central west greenland
Journal of Quaternary Science, 2014Co-Authors: Anne E Jennings, John T Andrews, Colm Ó Cofaigh, Mariah Walton, A A Kilfeather, Joseph D Ortiz, Anne De Vernal, Julian A. DowdeswellAbstract:Paleoenvironments during the late Younger Dryas through early Holocene retreat of the Greenland Ice Sheet from the outer shelf in the Disko Trough system of central West Greenland were investigated via lithofacies, foraminifera, dinocysts and sediment provenance analyses in radiocarbon-dated sediment cores from the upper slope (JR175-VC35) and outer shelf (JR175-VC20 and HU2008029-070CC). Core data show that the Ice margin retreated rapidly from the outer shelf by calving, beginning by 12.2k cal a BP under cold paleoceano- graphic conditions with up to 11 months of sea-Ice. Ice retreat into Disko Bugt was well underway by 10.9k cal a BP. Enhanced Ice-sheet ablation in Disko Bugt and elsewhere along the West Greenland coast is inferred from cold glacial marine conditions associated with high sedimentation rates between 10.9 and 9.5k cal a BP on the outer shelf. Glacial marine conditions are recorded on the outer shelf until 7.8k cal a BP. Detrital carbonate-bearing sediments rich in >2-mm clasts deposited between 11.6 and 10.6k cal a BP indicate that Icebergs calved from northern Baffin Bay Ice margins were melting and releasing sediments along West Greenland while the Greenland Ice Sheet margin was retreating into Disko Bugt. Copyright # 2013 John Wiley & Sons, Ltd.
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Paleoenvironments during Younger Dryas‐Early Holocene retreat of the Greenland Ice Sheet from outer Disko Trough, central west Greenland
Journal of Quaternary Science, 2013Co-Authors: Anne E Jennings, John T Andrews, Colm Ó Cofaigh, A A Kilfeather, Joseph D Ortiz, Anne De Vernal, Mariah E. Walton, Julian A. DowdeswellAbstract:Paleoenvironments during the late Younger Dryas through early Holocene retreat of the Greenland Ice Sheet from the outer shelf in the Disko Trough system of central West Greenland were investigated via lithofacies, foraminifera, dinocysts and sediment provenance analyses in radiocarbon-dated sediment cores from the upper slope (JR175-VC35) and outer shelf (JR175-VC20 and HU2008029-070CC). Core data show that the Ice margin retreated rapidly from the outer shelf by calving, beginning by 12.2k cal a BP under cold paleoceano- graphic conditions with up to 11 months of sea-Ice. Ice retreat into Disko Bugt was well underway by 10.9k cal a BP. Enhanced Ice-sheet ablation in Disko Bugt and elsewhere along the West Greenland coast is inferred from cold glacial marine conditions associated with high sedimentation rates between 10.9 and 9.5k cal a BP on the outer shelf. Glacial marine conditions are recorded on the outer shelf until 7.8k cal a BP. Detrital carbonate-bearing sediments rich in >2-mm clasts deposited between 11.6 and 10.6k cal a BP indicate that Icebergs calved from northern Baffin Bay Ice margins were melting and releasing sediments along West Greenland while the Greenland Ice Sheet margin was retreating into Disko Bugt. Copyright # 2013 John Wiley & Sons, Ltd.
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LATE QUATERNARY DETRITAL CARBONATE (DC-) LAYERS IN BAFFIN Bay MARINE SEDIMENTS (67°–74°N): CORRELATION WITH HEINRICH EVENTS IN THE NORTH ATLANTIC?
Quaternary Science Reviews, 1998Co-Authors: John T Andrews, Matthew E. Kirby, A. Aksu, Donald C. Barber, D. MeeseAbstract:Abstract Episodes of glaciation in the region north of Baffin Bay resulted in the erosion of Paleozoic carbonate outcrops in NW Greenland and the Canadian High Arctic. These events are recognized in the marine sediments of Baffin Bay (BB) as a series of detrital carbonate-rich (DC-) layers. BBDC-layers thin southward within Baffin Bay; thus, the contribution of Baffin Bay Ice-rafted carbonate-rich sediments to the North Atlantic is probably slight, especially compared with sediment output from Hudson Strait during Heinrich events. We reexamine (cf. Aksu, 1981) a series of nine piston cores from the axis of Baffin Bay and across the Davis Strait sill and provide a suite of 21 AMS 14 C dates on foramininfera which bracket the ages of several DC-layers. The onset of the last DC event is dated in six cores and has an age of ca. 12.4 ka. In northern and central Baffin Bay a thick DC-layer occurs at around 4 m in the cores and is dated >40 ka. There were three to six DC intervening events. The youngest BBDC event (possibly a double event) lags Heinrich event 1 (H-1) off Hudson Strait, dated at 14.5 ka, but it is coeval with the pronounced warming seen in GISP2 records from the Greenland Ice Sheet during interstadial #1. We hypothesize that BBDC episodes are coeval with major interstadial δ 18 O peaks from GISP2 and other Greenland Ice core records and are caused by or associated with the advection of Atlantic Water into Baffin Bay (cf. Hiscott et al ., 1989) and the subsequent rapid retreat of Ice streams in the northern approaches to Baffin Bay.
Colm Ó Cofaigh - One of the best experts on this subject based on the ideXlab platform.
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paleoenvironments during younger dryas early holocene retreat of the greenland Ice sheet from outer disko trough central west greenland
Journal of Quaternary Science, 2014Co-Authors: Anne E Jennings, John T Andrews, Colm Ó Cofaigh, Mariah Walton, A A Kilfeather, Joseph D Ortiz, Anne De Vernal, Julian A. DowdeswellAbstract:Paleoenvironments during the late Younger Dryas through early Holocene retreat of the Greenland Ice Sheet from the outer shelf in the Disko Trough system of central West Greenland were investigated via lithofacies, foraminifera, dinocysts and sediment provenance analyses in radiocarbon-dated sediment cores from the upper slope (JR175-VC35) and outer shelf (JR175-VC20 and HU2008029-070CC). Core data show that the Ice margin retreated rapidly from the outer shelf by calving, beginning by 12.2k cal a BP under cold paleoceano- graphic conditions with up to 11 months of sea-Ice. Ice retreat into Disko Bugt was well underway by 10.9k cal a BP. Enhanced Ice-sheet ablation in Disko Bugt and elsewhere along the West Greenland coast is inferred from cold glacial marine conditions associated with high sedimentation rates between 10.9 and 9.5k cal a BP on the outer shelf. Glacial marine conditions are recorded on the outer shelf until 7.8k cal a BP. Detrital carbonate-bearing sediments rich in >2-mm clasts deposited between 11.6 and 10.6k cal a BP indicate that Icebergs calved from northern Baffin Bay Ice margins were melting and releasing sediments along West Greenland while the Greenland Ice Sheet margin was retreating into Disko Bugt. Copyright # 2013 John Wiley & Sons, Ltd.
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Paleoenvironments during Younger Dryas‐Early Holocene retreat of the Greenland Ice Sheet from outer Disko Trough, central west Greenland
Journal of Quaternary Science, 2013Co-Authors: Anne E Jennings, John T Andrews, Colm Ó Cofaigh, A A Kilfeather, Joseph D Ortiz, Anne De Vernal, Mariah E. Walton, Julian A. DowdeswellAbstract:Paleoenvironments during the late Younger Dryas through early Holocene retreat of the Greenland Ice Sheet from the outer shelf in the Disko Trough system of central West Greenland were investigated via lithofacies, foraminifera, dinocysts and sediment provenance analyses in radiocarbon-dated sediment cores from the upper slope (JR175-VC35) and outer shelf (JR175-VC20 and HU2008029-070CC). Core data show that the Ice margin retreated rapidly from the outer shelf by calving, beginning by 12.2k cal a BP under cold paleoceano- graphic conditions with up to 11 months of sea-Ice. Ice retreat into Disko Bugt was well underway by 10.9k cal a BP. Enhanced Ice-sheet ablation in Disko Bugt and elsewhere along the West Greenland coast is inferred from cold glacial marine conditions associated with high sedimentation rates between 10.9 and 9.5k cal a BP on the outer shelf. Glacial marine conditions are recorded on the outer shelf until 7.8k cal a BP. Detrital carbonate-bearing sediments rich in >2-mm clasts deposited between 11.6 and 10.6k cal a BP indicate that Icebergs calved from northern Baffin Bay Ice margins were melting and releasing sediments along West Greenland while the Greenland Ice Sheet margin was retreating into Disko Bugt. Copyright # 2013 John Wiley & Sons, Ltd.
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Ice-stream stability on a reverse bed slope
Nature Geoscience, 2012Co-Authors: Stewart S. R. Jamieson, Andreas Vieli, Stephen J. Livingstone, Colm Ó Cofaigh, Chris R. Stokes, Claus-dieter Hillenbrand, Julian A. DowdeswellAbstract:Marine Ice streams whose beds deepen inland are thought to be inherently unstable. Numerical modelling of the Maguerite Bay Ice-stream retreat in West Antarctica since the Last Glacial Maximum suggests that an Ice stream can stabilize on an inland-sloping bed owing to increased lateral drag where the Ice stream narrows. Marine-based Ice streams whose beds deepen inland are thought to be inherently unstable1,2,3. This instability is of particular concern because significant portions of the marine-based West Antarctic and Greenland Ice sheets are losing mass and their retreat could contribute significantly to future sea-level rise4,5,6,7. However, the present understanding of Ice-stream stability is limited by observational records that are too short to resolve multi-decadal to millennial-scale behaviour or to validate numerical models8. Here we present a dynamic numerical simulation of Antarctic Ice-stream retreat since the Last Glacial Maximum (LGM), constrained by geophysical data, whose behaviour is consistent with the geomorphological record. We find that retreat of Marguerite Bay Ice Stream following the LGM was highly nonlinear and was interrupted by stabilizations on a reverse-sloping bed, where theory predicts rapid unstable retreat. We demonstrate that these transient stabilizations were caused by enhanced lateral drag as the Ice stream narrowed. We conclude that, as well as bed topography, Ice-stream width and long-term retreat history are crucial for understanding decadal- to centennial-scale Ice-stream behaviour and marine Ice-sheet vulnerability.
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Ice stream grounding-line stability on a reverse bed slope
2012Co-Authors: Stewart S. R. Jamieson, Andreas Vieli, Stephen J. Livingstone, Colm Ó Cofaigh, Chris R. Stokes, Claus-dieter Hillenbrand, Julian A. DowdeswellAbstract:Marine-based Ice streams whose beds deepen inland are thought to be inherently unstable1, 2, 3. This instability is of particular concern because significant portions of the marine-based West Antarctic and Greenland Ice sheets are losing mass and their retreat could contribute significantly to future sea-level rise4, 5, 6, 7. However, the present understanding of Ice-stream stability is limited by observational records that are too short to resolve multi-decadal to millennial-scale behaviour or to validate numerical models8. Here we present a dynamic numerical simulation of Antarctic Ice-stream retreat since the Last Glacial Maximum (LGM), constrained by geophysical data, whose behaviour is consistent with the geomorphological record. We find that retreat of Marguerite Bay Ice Stream following the LGM was highly nonlinear and was interrupted by stabilizations on a reverse-sloping bed, where theory predicts rapid unstable retreat. We demonstrate that these transient stabilizations were caused by enhanced lateral drag as the Ice stream narrowed. We conclude that, as well as bed topography, Ice-stream width and long-term retreat history are crucial for understanding decadal- to centennial-scale Ice-stream behaviour and marine Ice-sheet vulnerability.
Lauren J. Gregoire - One of the best experts on this subject based on the ideXlab platform.
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Simulating the Early Holocene demise of the Laurentide Ice Sheet with BISICLES (public trunk revision 3298)
Geoscientific Model Development, 2020Co-Authors: Ilkka S. O. Matero, Lauren J. Gregoire, Ruza F. IvanovicAbstract:Abstract. Simulating the demise of the Laurentide Ice Sheet covering Hudson Bay in the Early Holocene (10–7 ka) is important for understanding the role of accelerated changes in Ice sheet topography and melt in the 8.2 ka event, a century long cooling of the Northern Hemisphere by several degrees. Freshwater released from the Ice sheet through a surface mass balance instability (known as the saddle collapse) has been suggested as a major forcing for the 8.2 ka event, but the temporal evolution of this pulse has not been constrained. Dynamical Ice loss and marine interactions could have significantly accelerated the Ice sheet demise, but simulating such processes requires computationally expensive models that are difficult to configure and are often impractical for simulating past Ice sheets. Here, we developed an Ice sheet model setup for studying the Laurentide Ice Sheet's Hudson Bay saddle collapse and the associated meltwater pulse in unprecedented detail using the BISICLES Ice sheet model, an efficient marine Ice sheet model of the latest generation which is capable of refinement to kilometre-scale resolutions and higher-order Ice flow physics. The setup draws on previous efforts to model the deglaciation of the North American Ice Sheet for initialising the Ice sheet temperature, recent Ice sheet reconstructions for developing the topography of the region and Ice sheet, and output from a general circulation model for a representation of the climatic forcing. The modelled deglaciation is in agreement with the reconstructed extent of the Ice sheet, and the associated meltwater pulse has realistic timing. Furthermore, the peak magnitude of the modelled meltwater equivalent (0.07–0.13 Sv) is compatible with geological estimates of freshwater discharge through the Hudson Strait. The results demonstrate that while improved representations of the glacial dynamics and marine interactions are key for correctly simulating the pattern of Early Holocene Ice sheet retreat, surface mass balance introduces by far the most uncertainty. The new model configuration presented here provides future opportunities to quantify the range of plausible amplitudes and durations of a Hudson Bay Ice saddle collapse meltwater pulse and its role in forcing the 8.2 ka event.
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Simulating the Early Holocene demise of the Laurentide Ice Sheet with BISICLES (public trunk revision 3298)
2019Co-Authors: Ilkka Matero, Lauren J. Gregoire, Ruza F. IvanovicAbstract:Abstract. Simulating the demise of the Laurentide Ice Sheet covering the Hudson Bay in the early Holocene (10-7 ka) is important for understanding the role of accelerated changes in Ice sheet topography and melt in the 8.2 ka event , a century long cooling of the Northern Hemisphere by several degrees. Freshwater released from the Ice sheet through a surface mass balance instability (known as the saddle collapse) has been suggested as a major forcing for the 8.2 ka event, but the temporal evolution of this pulse has not been constrained. Dynamical Ice loss and marine interactions could have significantly accelerated the Ice sheet demise, but simulating such processes requires computationally expensive models that are difficult to configure and are often impractical for simulating past Ice sheets. Here, we developed an Ice sheet model setup for studying the Laurentide Ice Sheet’s Hudson Bay saddle collapse and the associated meltwater pulse in unprecedented detail using the BISICLES Ice sheet model, an efficient marine Ice sheet model of the latest generation, capable of refinement to kilometre-scale resolution and higher-order Ice flow physics. The setup draws on previous efforts to model the deglaciation of the North American Ice Sheet for initialising the Ice sheet temperature, recent Ice sheet reconstructions for developing the topography of the region and Ice sheet, and output from a general circulation model for a representation of the climatic forcing. The modelled deglaciation is in agreement with the reconstructed extent of the Ice sheet and the associated meltwater pulse has realistic timing. Furthermore,the peak magnitude of the modelled meltwater equivalent (0.07–0.13 Sv) is compatible with geological estimates of freshwater discharge through the Hudson Strait. The results demonstrate that while improved representation of the glacial dynamics and marine interactions are key for correctly simulating the pattern of early Holocene Ice sheet retreat, surface mass balance introduces by far the most uncertainty. The new model configuration presented here provides future opportunities to quantify the range of plausible amplitudes and durations of a Hudson Bay Ice saddle collapse meltwater pulse and its role in forcing the 8.2 ka event.
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The 8.2 ka cooling event caused by Laurentide Ice saddle collapse
Earth and Planetary Science Letters, 2017Co-Authors: Ilkka Matero, Lauren J. Gregoire, Ruza F. Ivanovic, Julia C. Tindall, Alan M. HaywoodAbstract:Abstract The 8.2 ka event was a period of abrupt cooling of 1–3 °C across large parts of the Northern Hemisphere, which lasted for about 160 yr. The original hypothesis for the cause of this event has been the outburst of the proglacial Lakes Agassiz and Ojibway. These drained into the Labrador Sea in ∼0.5–5 yr and slowed the Atlantic Meridional Overturning Circulation, thus cooling the North Atlantic region. However, climate models have not been able to reproduce the duration and magnitude of the cooling with this forcing without including additional centennial-length freshwater forcings, such as rerouting of continental runoff and Ice sheet melt in combination with the lake release. Here, we show that instead of being caused by the lake outburst, the event could have been caused by accelerated melt from the collapsing Ice saddle that linked domes over Hudson Bay in North America. We forced a General Circulation Model with time varying meltwater pulses (100–300 yr) that match observed sea level change, designed to represent the Hudson Bay Ice saddle collapse. A 100 yr long pulse with a peak of 0.6 Sv produces a cooling in central Greenland that matches the 160 yr duration and 3 °C amplitude of the event recorded in Ice cores. The simulation also reproduces the cooling pattern, amplitude and duration recorded in European Lake and North Atlantic sediment records. Such abrupt acceleration in Ice melt would have been caused by surface melt feedbacks and marine Ice sheet instability. These new realistic forcing scenarios provide a means to reconcile longstanding mismatches between proxy data and models, allowing for a better understanding of both the sensitivity of the climate models and processes and feedbacks in motion during the disintegration of continental Ice sheets.
