scholarly journals The Antarctic Ice Sheet response to glacial millennial scale variability

2018 ◽  
Author(s):  
Javier Blasco ◽  
Ilaria Tabone ◽  
Jorge Alvarez-Solas ◽  
Alexander Robinson ◽  
Marisa Montoya
Keyword(s):  
Sea Level ◽  
Three Dimensional ◽  
Ice Sheets ◽  
Ice Sheet ◽  
Climate Impacts ◽  
Strong Impact ◽  
Appreciable Effect ◽  
Antarctic Ice Sheet ◽  
The Antarctic ◽  
Millennial Scale

Abstract. The Antarctic Ice Sheet (AIS) is the largest ice sheet on Earth and hence a major potential contributor to future global sea-level rise. A wealth of studies suggest that increasing oceanic temperatures could cause a collapse of its marine-based western sector, the West Antarctic Ice Sheet, through the mechanism of marine ice-sheet instability, leading to a sea-level increase of 3–5 m. Thus, it is crucial to constrain the sensitivity of the AIS to rapid climate changes. The Last Glacial Period is an ideal benchmark period for this purpose as it was punctuated by abrupt Dansgaard-Oeschger events at millennial timescales. Because their centre of action was in the North Atlantic, where their climate impacts were largest, modelling studies have mainly focused on the millennial-scale evolution of Northern Hemisphere (NH) paleo ice sheets. Sea-level reconstructions attribute the origin of millennial-scale sea-level variations mainly to NH paleo ice sheets, with a minor but not negligible role to the AIS. Here we investigate the AIS response to millennial-scale climate variability for the first time. To this end we use a three-dimensional, thermomechanical hybrid, ice-sheet-shelf model. Different oceanic sensitivities are tested and the sea-level equivalent (SLE) contributions computed. We find that whereas atmospheric variability has no appreciable effect on the AIS, changes in submarine melting rates can have a strong impact on it. We show that in contrast to the widespread assumption that the AIS is a slow reactive and static ice sheet that responds at orbital timescales only, it can lead to ice discharges of almost 15 m of SLE involving substantial grounding line migrations at millennial timescales.

scholarly journals The Antarctic Ice Sheet response to glacial millennial-scale variability

2019 ◽  
Vol 15 (1) ◽  
pp. 121-133 ◽  
Author(s):  
Javier Blasco ◽  
Ilaria Tabone ◽  
Jorge Alvarez-Solas ◽  
Alexander Robinson ◽  
Marisa Montoya
Keyword(s):  
Sea Level ◽  
Three Dimensional ◽  
Ice Sheets ◽  
Ice Sheet ◽  
Climate Impacts ◽  
Strong Impact ◽  
Appreciable Effect ◽  
Antarctic Ice Sheet ◽  
The Antarctic ◽  
Millennial Scale

Abstract. The Antarctic Ice Sheet (AIS) is the largest ice sheet on Earth and hence a major potential contributor to future global sea-level rise. A wealth of studies suggest that increasing oceanic temperatures could cause a collapse of its marine-based western sector, the West Antarctic Ice Sheet, through the mechanism of marine ice-sheet instability, leading to a sea-level increase of 3–5 m. Thus, it is crucial to constrain the sensitivity of the AIS to rapid climate changes. The last glacial period is an ideal benchmark period for this purpose as it was punctuated by abrupt Dansgaard–Oeschger events at millennial timescales. Because their center of action was in the North Atlantic, where their climate impacts were largest, modeling studies have mainly focused on the millennial-scale evolution of Northern Hemisphere (NH) paleo ice sheets. Sea-level reconstructions attribute the origin of millennial-scale sea-level variations mainly to NH paleo ice sheets, with a minor but not negligible role of the AIS. Here we investigate the AIS response to millennial-scale climate variability for the first time. To this end we use a three-dimensional, thermomechanical hybrid, ice sheet–shelf model. Different oceanic sensitivities are tested and the sea-level equivalent (SLE) contributions computed. We find that whereas atmospheric variability has no appreciable effect on the AIS, changes in submarine melting rates can have a strong impact on it. We show that in contrast to the widespread assumption that the AIS is a slow reactive and static ice sheet that responds at orbital timescales only, it can lead to ice discharges of around 6 m SLE, involving substantial grounding line migrations at millennial timescales.

scholarly journals Simulating the Antarctic ice sheet in the Late-Pliocene warm period: PLISMIP-ANT, an ice-sheet model intercomparison project

2014 ◽  
Vol 8 (6) ◽  
pp. 5539-5588 ◽  
Author(s):  
B. de Boer ◽  
A. M. Dolan ◽  
J. Bernales ◽  
E. Gasson ◽  
H. Goelzer ◽  
...  
Keyword(s):  
Sea Level Rise ◽  
Sea Level ◽  
Ice Sheets ◽  
Ice Sheet ◽  
Warm Period ◽  
Antarctic Ice Sheet ◽  
Late Pliocene ◽  
Bedrock Topography ◽  
Intercomparison Project ◽  
The Antarctic

Abstract. In the context of future climate change, understanding the nature and behaviour of ice sheets during warm intervals in Earth history is of fundamental importance. The Late-Pliocene warm period (also known as the PRISM interval: 3.264 to 3.025 million years before present) can serve as a potential analogue for projected future climates. Although Pliocene ice locations and extents are still poorly constrained, a significant contribution to sea-level rise should be expected from both the Greenland ice sheet and the West and East Antarctic ice sheets based on palaeo sea-level reconstructions. Here, we present results from simulations of the Antarctic ice sheet by means of an international Pliocene Ice Sheet Modeling Intercomparison Project (PLISMIP-ANT). For the experiments, ice-sheet models including the shallow ice and shelf approximations have been used to simulate the complete Antarctic domain (including grounded and floating ice). We compare the performance of six existing numerical ice-sheet models in simulating modern control and Pliocene ice sheets by a suite of four sensitivity experiments. Ice-sheet model forcing fields are taken from the HadCM3 atmosphere–ocean climate model runs for the pre-industrial and the Pliocene. We include an overview of the different ice-sheet models used and how specific model configurations influence the resulting Pliocene Antarctic ice sheet. The six ice-sheet models simulate a comparable present-day ice sheet, although the models are setup with their own parameter settings. For the Pliocene simulations using the Bedmap1 bedrock topography, some models show a small retreat of the East Antarctic ice sheet, which is thought to have happened during the Pliocene for the Wilkes and Aurora basins. This can be ascribed to either the surface mass balance, as the HadCM3 Pliocene climate shows a significant increase over the Wilkes and Aurora basin, or the initial bedrock topography. For the latter, our simulations with the recently published Bedmap2 bedrock topography indicate a significantly larger contribution to Pliocene sea-level rise from the East Antarctic ice sheet for all six models relative to the simulations with Bedmap1.

scholarly journals Sensitivity of the Antarctic ice sheets to the warming of marine isotope substage 11c

2021 ◽  
Vol 15 (1) ◽  
pp. 459-478
Author(s):  
Martim Mas e Braga ◽  
Jorge Bernales ◽  
Matthias Prange ◽  
Arjen P. Stroeven ◽  
Irina Rogozhina
Keyword(s):  
Sea Level ◽  
Ice Sheets ◽  
Ice Sheet ◽  
Antarctic Ice Sheet ◽  
Climate Signal ◽  
West Antarctic Ice Sheet ◽  
Climate Conditions ◽  
West Antarctic ◽  
The Antarctic ◽  
Antarctic Ice Sheets

Abstract. Studying the response of the Antarctic ice sheets during periods when climate conditions were similar to the present can provide important insights into current observed changes and help identify natural drivers of ice sheet retreat. In this context, the marine isotope substage 11c (MIS11c) interglacial offers a suitable scenario, given that during its later portion orbital parameters were close to our current interglacial. Ice core data indicate that warmer-than-present temperatures lasted for longer than during other interglacials. However, the response of the Antarctic ice sheets and their contribution to sea level rise remain unclear. We explore the dynamics of the Antarctic ice sheets during this period using a numerical ice sheet model forced by MIS11c climate conditions derived from climate model outputs scaled by three glaciological and one sedimentary proxy records of ice volume. Our results indicate that the East and West Antarctic ice sheets contributed 4.0–8.2 m to the MIS11c sea level rise. In the case of a West Antarctic Ice Sheet collapse, which is the most probable scenario according to far-field sea level reconstructions, the range is reduced to 6.7–8.2 m independently of the choices of external sea level forcing and millennial-scale climate variability. Within this latter range, the main source of uncertainty arises from the sensitivity of the East Antarctic Ice Sheet to a choice of initial ice sheet configuration. We found that the warmer regional climate signal captured by Antarctic ice cores during peak MIS11c is crucial to reproduce the contribution expected from Antarctica during the recorded global sea level highstand. This climate signal translates to a modest threshold of 0.4 ∘C oceanic warming at intermediate depths, which leads to a collapse of the West Antarctic Ice Sheet if sustained for at least 4000 years.

Sensitivity of the Antarctic ice sheets to the warming of MIS11c

2021 ◽  
Author(s):  
Martim Mas e Braga ◽  
Jorge Bernales ◽  
Matthias Prange ◽  
Arjen P. Stroeven ◽  
Irina Rogozhina
Keyword(s):  
Sea Level ◽  
Climate Model ◽  
Ice Sheets ◽  
Ice Sheet ◽  
Antarctic Ice Sheet ◽  
West Antarctic Ice Sheet ◽  
Climate Conditions ◽  
West Antarctic ◽  
The Antarctic ◽  
Antarctic Ice Sheets

<p><span><span>The Marine Isotope Substage 11c (MIS11c) interglacial (425 – 395 thousand years before present) is a useful analogue to climate conditions that can be expected in the near future, and can provide insights on the natural response of the Antarctic ice sheets to a moderate, yet long lasting warming period. However, its response to the warming of MIS11c and consequent contribution to global sea level rise still remains unclear. We explore the dynamics of the Antarctic ice sheets during this period using a numerical ice-sheet model forced by MIS11c climate conditions derived from climate model outputs scaled by three ice core and one sedimentary proxy records of ice volume. We identify a tipping point beyond which oceanic warming becomes the dominant forcing of ice-sheet retreat, and where collapse of the West Antarctic Ice Sheet is attained when a threshold of 0.4 </span></span><sup><span><span>o</span></span></sup><span><span>C oceanic warming relative to Pre-Industrial levels is sustained for at least 4 thousand years. Conversely, its eastern counterpart remains relatively stable, as it is mostly grounded above sea level. Our results suggest a total sea level contribution from the East and West Antarctic ice sheets of 4.0 – 8.2 m during MIS11c. In the case of a West Antarctic Ice Sheet collapse, which is the most probable scenario according to far-field sea-level reconstructions, this range is reduced to 6.7 – 8.2 m, and mostly reflects uncertainties regarding the initial configuration of the East Antarctic Ice Sheet. </span></span></p>

scholarly journals Simulating the Antarctic ice sheet in the late-Pliocene warm period: PLISMIP-ANT, an ice-sheet model intercomparison project

2015 ◽  
Vol 9 (3) ◽  
pp. 881-903 ◽  
Author(s):  
B. de Boer ◽  
A. M. Dolan ◽  
J. Bernales ◽  
E. Gasson ◽  
H. Goelzer ◽  
...  
Keyword(s):  
Sea Level ◽  
Ice Sheets ◽  
Ice Sheet ◽  
Warm Period ◽  
Future Climate Change ◽  
Antarctic Ice Sheet ◽  
Late Pliocene ◽  
Grounding Line ◽  
Intercomparison Project ◽  
The Antarctic

Abstract. In the context of future climate change, understanding the nature and behaviour of ice sheets during warm intervals in Earth history is of fundamental importance. The late Pliocene warm period (also known as the PRISM interval: 3.264 to 3.025 million years before present) can serve as a potential analogue for projected future climates. Although Pliocene ice locations and extents are still poorly constrained, a significant contribution to sea-level rise should be expected from both the Greenland ice sheet and the West and East Antarctic ice sheets based on palaeo sea-level reconstructions. Here, we present results from simulations of the Antarctic ice sheet by means of an international Pliocene Ice Sheet Modeling Intercomparison Project (PLISMIP-ANT). For the experiments, ice-sheet models including the shallow ice and shelf approximations have been used to simulate the complete Antarctic domain (including grounded and floating ice). We compare the performance of six existing numerical ice-sheet models in simulating modern control and Pliocene ice sheets by a suite of five sensitivity experiments. We include an overview of the different ice-sheet models used and how specific model configurations influence the resulting Pliocene Antarctic ice sheet. The six ice-sheet models simulate a comparable present-day ice sheet, considering the models are set up with their own parameter settings. For the Pliocene, the results demonstrate the difficulty of all six models used here to simulate a significant retreat or re-advance of the East Antarctic ice grounding line, which is thought to have happened during the Pliocene for the Wilkes and Aurora basins. The specific sea-level contribution of the Antarctic ice sheet at this point cannot be conclusively determined, whereas improved grounding line physics could be essential for a correct representation of the migration of the grounding-line of the Antarctic ice sheet during the Pliocene.

The climatic effects of large-scale surges of ice sheets

1969 ◽  
Vol 6 (4) ◽  
pp. 911-918 ◽  
Author(s):  
A. T. Wilson
Keyword(s):  
Sea Level ◽  
Large Scale ◽  
Ice Sheets ◽  
Ice Sheet ◽  
Considerable Effect ◽  
Ice Age ◽  
Ice Shelf ◽  
Climatic Effects ◽  
Antarctic Ice Sheet ◽  
The Antarctic

Surges in ice masses of glacier size are now well accepted in glaciology. There seems no reason why a similar phenomenon should not occur in bodies of ice as large as continental ice sheets.If a continental ice sheet surged into the sea it would have a considerable effect on world sea-level. This is proposed as the mechanism of past sea-level fluctuations (cyclothems) of the Carboniferous and Tertiary.The effect of a surge of the Antarctic Ice Sheet on world climate is considered, with particular reference to the origin of ice ages.The requirements of an ice-age mechanism are discussed and it is concluded that a periodic surge of the Antarctic Ice Sheet, perhaps induced by a decrease in insolation to the south polar region, has all the requirements of an ice-age inducing mechanism. In particular, any oscillating system must have capacitance (storage) and impedance (resistance). It is not easy to find a system in nature with a sufficiently long period of oscillation. However, the build up of ice on Antarctica would provide a sufficiently slow charging of storage, and the ice sheet itself would provide the storage to yield a system of long enough period.It is proposed that when the Antarctic Ice Sheet surges, a large ice shelf is produced which increases the albedo of the Earth. The resulting cooling leads to the formation of secondary ice sheets in the Northern Hemisphere, which in turn leads to a further increase in albedo and further cooling. The break up of the ice shelf and its replacement by ocean would lead to a large decrease in the Earth's albedo. The resulting warming would lead to the rapid melting of the subsiduary ice sheets and the ending of the ice age.

scholarly journals Satellite gravity and the mass balance of the antarctic ice sheet

1998 ◽  
Vol 44 (147) ◽  
pp. 207-213 ◽  
Author(s):  
C. R. Bentley ◽  
J. M. Wahr
Keyword(s):  
Sea Level ◽  
Ice Sheets ◽  
Ice Sheet ◽  
Satellite Gravity ◽  
Antarctic Ice Sheet ◽  
Level Change ◽  
Gravity Measurements ◽  
The Antarctic ◽  
Gravity Mission

AbstractChanges in the Earth’s gravity field with time have important applications to a broad range of disciplines. Any process that involves a large enough horizontal redistribution of mass, either within the Earth or on or above its surface, is potentially detectable. In particular, when ice sheets grow or shrink, gravity changes as mass is redistributed in the solid earth and between the oceans and the ice sheets. The sources of global sea-level rise (about 2 mm a−1 over the last century) and in particular the contribution of the Antarctic ice sheet thereto are not well understood. Gravity measurements can help to diminish this uncertainty.The technology currently exists to measure gravity with high accuracy by a dual-satellite mission in which the distance between the satellites is precisely monitored. We estimate from recent studies that temporal changes in the gravity field as determined by a satellite gravity mission lasting 5 years at an orbital height of 400 km would be sensitive to changes in the overall mass of the Antarctic ice sheet to a precision corresponding to better than 0.01 mm a−1 of sea-level change. However, the effects of three other phenomena that could each produce a temporally varying gravity signal with characteristics comparable to that caused by a change in Antarctic ice—postglacial rebound, inter-annual variability in snowfall, and atmospheric pressure trends — also need to be evaluated. Postglacial rebound could be partly separated from ice-mass changes with the aid of global positioning system campaigns and numerical models of rebound that use improved determinations of mantle viscosity also provided by the gravity mission. Determination of inter-annual ice-mass changes will be aided by measurements of moisture-flux divergence around the perimeters of the ice sheets and direct observations of inter-annual changes by the gravity satellite itself. The removal of pressure effects over Antarctica will become more effective as the number of automatic weather stations in the interior of the continent increases.Even after corrections are made for these factors, the uncertainties they cause limit the accuracy in the détermination of the contribution of the Antarctic ice sheet to sea-level change to about 0.5 mm a−1. However, there is a strong complementarity between gravity measurements and the surface-height measurements that will be produced by NASA’s laser altimeter mission early next century. Together, they should be able to determine that contribution to an accuracy of about 0.1 mm a−1.

scholarly journals Sensitivity of the Antarctic ice sheets to the peak warming of Marine Isotope Stage 11

2020 ◽  
Author(s):  
Martim Mas e Braga ◽  
Jorge Bernales ◽  
Matthias Prange ◽  
Arjen P. Stroeven ◽  
Irina Rogozhina
Keyword(s):  
Sea Level ◽  
Regional Climate ◽  
Ice Core ◽  
Ice Sheets ◽  
Ice Sheet ◽  
Initial Configuration ◽  
Antarctic Ice Sheet ◽  
Climate Conditions ◽  
The Antarctic ◽  
Antarctic Ice Sheets

Abstract. Studying the response of the Antarctic ice sheets to past climate conditions similar to the present day can provide important insights for understanding its current changes and help identify natural drivers of ice sheet retreat. The Marine Isotope Substage 11c (MIS11c) interglacial is one of the best candidates for an in-depth analysis given that at its later portion orbital parameters were close to our current interglacial. However, Antarctic ice core data indicate that although MIS11c CO2 levels were close to Pre Industrial, warmer-than-present temperatures (of about 2 °C) lasted for much longer than during other interglacials. Since the global mean sea level is thought to have been 6‐13 m higher than today, there should have been some contribution from Antarctica. While substantial work has been conducted regarding the response of the Greenland Ice Sheet to the MIS11c climate, which is believed to have contributed with 3.9–7.0 m to global sea level, both configurations of the Antarctic ice sheets and their contribution to sea level rise remain poorly constrained. We use a numerical ice-sheet model to shed light on the response of the Antarctic ice sheets to MIS11c climate conditions obtained from a combination of a suite of Antarctic ice cores and the LR04 global stack of deep-sea sediment records and climate model outputs, while assessing the model sensitivity to the uncertainties in sea level reconstructions, ice sheet initial configuration, and multi-centennial climate variability. We found that the regional climate signal of the MIS11c peak warming in Antarctica captured by the ice core records is necessary for the recorded sea level highstand to be reproduced, and that warming length was more important than magnitude. However, there is a threshold for a West Antarctic Ice Sheet collapse that lies within an envelope of 1.6 and 2.1 °C warmer-than-pre-industrial regional climate conditions. Sea level forcing and multi-centennial variability were found to have played virtually no role in driving ice sheet contraction, but the choice of initial configuration of the East Antarctic Ice Sheet provided a large source of uncertainty in the quantification of MIS11c Antarctic peak sea level contribution, which falls between 6.4 and 8.8 m.

scholarly journals Satellite gravity and the mass balance of the antarctic ice sheet

1998 ◽  
Vol 44 (147) ◽  
pp. 207-213 ◽  
Author(s):  
C. R. Bentley ◽  
J. M. Wahr
Keyword(s):  
Sea Level ◽  
Ice Sheets ◽  
Ice Sheet ◽  
Satellite Gravity ◽  
Antarctic Ice Sheet ◽  
Level Change ◽  
Gravity Measurements ◽  
The Antarctic ◽  
Gravity Mission

AbstractChanges in the Earth’s gravity field with time have important applications to a broad range of disciplines. Any process that involves a large enough horizontal redistribution of mass, either within the Earth or on or above its surface, is potentially detectable. In particular, when ice sheets grow or shrink, gravity changes as mass is redistributed in the solid earth and between the oceans and the ice sheets. The sources of global sea-level rise (about 2 mm a−1over the last century) and in particular the contribution of the Antarctic ice sheet thereto are not well understood. Gravity measurements can help to diminish this uncertainty.The technology currently exists to measure gravity with high accuracy by a dual-satellite mission in which the distance between the satellites is precisely monitored. We estimate from recent studies that temporal changes in the gravity field as determined by a satellite gravity mission lasting 5 years at an orbital height of 400 km would be sensitive to changes in the overall mass of the Antarctic ice sheet to a precision corresponding to better than 0.01 mm a−1of sea-level change. However, the effects of three other phenomena that could each produce a temporally varying gravity signal with characteristics comparable to that caused by a change in Antarctic ice—postglacial rebound, inter-annual variability in snowfall, and atmospheric pressure trends — also need to be evaluated. Postglacial rebound could be partly separated from ice-mass changes with the aid of global positioning system campaigns and numerical models of rebound that use improved determinations of mantle viscosity also provided by the gravity mission. Determination of inter-annual ice-mass changes will be aided by measurements of moisture-flux divergence around the perimeters of the ice sheets and direct observations of inter-annual changes by the gravity satellite itself. The removal of pressure effects over Antarctica will become more effective as the number of automatic weather stations in the interior of the continent increases.Even after corrections are made for these factors, the uncertainties they cause limit the accuracy in the détermination of the contribution of the Antarctic ice sheet to sea-level change to about 0.5 mm a−1. However, there is a strong complementarity between gravity measurements and the surface-height measurements that will be produced by NASA’s laser altimeter mission early next century. Together, they should be able to determine that contribution to an accuracy of about 0.1 mm a−1.

Estimating Antarctic Ice Sheet Contributions to Future Sea Level Rise Using a Coupled Climate-Ice Sheet Model

2020 ◽  
Author(s):  
Jun-Young Park ◽  
Fabian Schloesser ◽  
Axel Timmermann ◽  
Dipayan Choudhury ◽  
June-Yi Lee ◽  
...  
Keyword(s):  
Sea Level ◽  
Three Dimensional ◽  
Ice Sheet ◽  
Antarctic Ice Sheet ◽  
Mean Sea Level ◽  
Future Warming ◽  
Ice Sheet Dynamics ◽  
Global Mean Sea Level ◽  
The Antarctic ◽  
Global Mean

<p>One of the largest uncertainties in projecting future global mean sea level (GSML) rise in response to anthropogenic global warming originates from the Antarctic ice sheet (AIS) contribution. Previous studies suggested that a potential AIS collapse due to the Marine Ice Sheet Instability (MISI) and Marine Ice Cliff Instability (MICI) may contribute up to 1m GMSL rise by the year 2100. However, these estimates were based on uncoupled ice sheet models that do not capture interactions between the AIS and the ocean and atmosphere. Here, we explore future GMSL projections using a three-dimensional coupled climate-ice sheet model (LOVECLIP) that simulates ice sheet dynamics in both hemispheres. The model was forced by increasing CO<sub>2</sub> concentrations following the Shared Socioeconomic Pathway (SSP) 1-1.9, 2-4.5 and 5-8.5 scenarios. Over the next 80 years, the corresponding GMSL contribution from AIS amounts to about 2cm, 8cm and 11cm, respectively. Additional sensitivity experiments show that AIS meltwater flux in response to the SSP 5-8.5 CO<sub>2</sub> concentrations causes subsurface Southern Ocean warming which leads to an additional 20% AIS melting and a reduction in Southern Hemispheric future warming.</p>

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