Rapid sea-level rise along the Antarctic margins in response to increased glacial discharge

Mass loss of the Antarctic ice sheet contributes the largest uncertainty of future sea-level rise projections. Ice-sheet model predictions are limited by uncertainties in climate forcing and poor understanding of processes such as ice viscosity. The Antarctic BUttressing Model Intercomparison Project (ABUMIP) has investigated the 'end-member' scenario, i.e., a total and sustained removal of buttressing from all Antarctic ice shelves, which can be regarded as the upper-bound physical possible, but implausible contribution of sea-level rise due to ice-shelf loss. In this study, we add successive layers of &#8216;realism&#8217; to the ABUMIP scenario by considering sustained regional ice-shelf collapse and by introducing ice-shelf regrowth after collapse with the inclusion of ice-sheet and ice-shelf damage (Sun et al., 2017). Ice shelf regrowth has the ability to stabilize grounding lines, while ice shelf damage may reinforce ice loss. In combination with uncertainties from basal sliding and ice rheology, a more realistic physical upperbound to ice loss is sought. Results are compared in the light of other proposed mechanisms, such as MICI due to ice cliff collapse.

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Antarctic Ice-Sheet Volume at 18000 Years B.P. and Holocene Sea-Level Changes at the West Antarctic Margin

Journal of Glaciology ◽

10.3189/s0022143000014751 ◽

1979 ◽

Vol 24 (90) ◽

pp. 213-230 ◽

Cited By ~ 1

Author(s):

Craig S. Lingle ◽

James A. Clark

Keyword(s):

Sea Level Rise ◽

Sea Level ◽

Ice Sheet ◽

Sea Level Changes ◽

Ice Shelf ◽

Relative Sea Level ◽

Antarctic Ice Sheet ◽

West Antarctic Ice Sheet ◽

West Antarctic ◽

The Antarctic

AbstractThe Antarctic ice sheet has been reconstructed at 18000 years b.p. by Hughes and others (in press) using an ice-flow model. The volume of the portion of this reconstruction which contributed to a rise of post-glacial eustatic sea-level has been calculated and found to be (9.8±1.5) × 106 km3. This volume is equivalent to 25±4 m of eustatic sea-level rise, defined as the volume of water added to the ocean divided by ocean area. The total volume of the reconstructed Antarctic ice sheet was found to be (37±6) × 106 km3. If the results of Hughes and others are correct, Antarctica was the second largest contributor to post-glacial eustatic sea-level rise after the Laurentide ice sheet. The Farrell and Clark (1976) model for computation of the relative sea-level changes caused by changes in ice and water loading on a visco-elastic Earth has been applied to the ice-sheet reconstruction, and the results have been combined with the changes in relative sea-level caused by Northern Hemisphere deglaciation as previously calculated by Clark and others (1978). Three families of curves have been compiled, showing calculated relative sea-level change at different times near the margin of the possibly unstable West Antarctic ice sheet in the Ross Sea, Pine Island Bay, and the Weddell Sea. The curves suggest that the West Antarctic ice sheet remained grounded to the edge of the continental shelf until c. 13000 years b.p., when the rate of sea-level rise due to northern ice disintegration became sufficient to dominate emergence near the margin predicted otherwise to have been caused by shrinkage of the Antarctic ice mass. In addition, the curves suggest that falling relative sea-levels played a significant role in slowing and, perhaps, reversing retreat when grounding lines approached their present positions in the Ross and Weddell Seas. A predicted fall of relative sea-level beneath the central Ross Ice Shelf of as much as 23 m during the past 2000 years is found to be compatible with recent field evidence that the ice shelf is thickening in the south-east quadrant.

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Delaying future sea-level rise by storing water in Antarctica

Earth System Dynamics ◽

10.5194/esd-7-203-2016 ◽

2016 ◽

Vol 7 (1) ◽

pp. 203-210 ◽

Cited By ~ 13

Author(s):

K. Frieler ◽

M. Mengel ◽

A. Levermann

Keyword(s):

Sea Level Rise ◽

Sea Level ◽

Energy Supply ◽

Primary Energy ◽

Ocean Water ◽

Additional Mass ◽

Dynamic Perspective ◽

Primary Energy Supply ◽

The Antarctic

Abstract. Even if greenhouse gas emissions were stopped today, sea level would continue to rise for centuries, with the long-term sea-level commitment of a 2 °C warmer world significantly exceeding 2 m. In view of the potential implications for coastal populations and ecosystems worldwide, we investigate, from an ice-dynamic perspective, the possibility of delaying sea-level rise by pumping ocean water onto the surface of the Antarctic ice sheet. We find that due to wave propagation ice is discharged much faster back into the ocean than would be expected from a pure advection with surface velocities. The delay time depends strongly on the distance from the coastline at which the additional mass is placed and less strongly on the rate of sea-level rise that is mitigated. A millennium-scale storage of at least 80 % of the additional ice requires placing it at a distance of at least 700 km from the coastline. The pumping energy required to elevate the potential energy of ocean water to mitigate the currently observed 3 mm yr−1 will exceed 7 % of the current global primary energy supply. At the same time, the approach offers a comprehensive protection for entire coastlines particularly including regions that cannot be protected by dikes.

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Impact of transient increases in atmospheric CO2 on the accumulation and mass balance of the Antarctic ice sheet

Annals of Glaciology ◽

10.1017/s0260305500013938 ◽

1997 ◽

Vol 25 ◽

pp. 137-144 ◽

Cited By ~ 6

Author(s):

Siobhan P. O’Farrell ◽

John L. McGregor ◽

Leon D. Rotstayn ◽

William F. Budd ◽

Christopher Zweck ◽

...

Keyword(s):

Sea Level Rise ◽

Sea Level ◽

Ice Sheet ◽

Coupled Model ◽

Negative Contribution ◽

Antarctic Ice Sheet ◽

Ice Shelves ◽

Basal Melting ◽

Main Effects ◽

The Antarctic

The response of the Antarctic ice sheet to climate change over the next 500 years is calculated using the output of a transient-coupled ocean-atmosphere simulation assuming the atmospheric CO2value increases up to three times present levels. The main effects on the ice sheet on this time-scale include increasing rates of accumulation, minimal surface melting, and basal melting of ice shelves. A semi-Lagrangian transport scheme for moisture was used to improve the model’s ability to represent realistic rates of accumulation under present-day conditions, and thereby increase confidence in the anomalies calculated under a warmer climate. The response of the Antarctic ice sheet to the warming is increased accumulation inland, offset by loss from basal melting from the floating ice, and increased ice flow near the grounding line. The preliminary results of this study show that the change to the ice-sheet balance for the transient-coupled model forcing amounted to a minimal sea-level contribution in the next century, but a net positive sea-level rise of 0.21 m by 500 years. This new result supercedes earlier results that showed the Antarctic ice sheet made a net negative contribution to sea-level rise over the next century. However, the amplitude of the sea-level rise is still dominated In the much larger contributions expected from thermal expansion of the ocean of 0.25 m for 100 years and 1.00 m for 500 years.

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Combustion of available fossil fuel resources sufficient to eliminate the Antarctic Ice Sheet

Science Advances ◽

10.1126/sciadv.1500589 ◽

2015 ◽

Vol 1 (8) ◽

pp. e1500589 ◽

Cited By ~ 59

Author(s):

Ricarda Winkelmann ◽

Anders Levermann ◽

Andy Ridgwell ◽

Ken Caldeira

Keyword(s):

Sea Level Rise ◽

Sea Level ◽

Carbon Emissions ◽

Fossil Fuel ◽

Ice Sheet ◽

Antarctic Ice Sheet ◽

West Antarctic Ice Sheet ◽

West Antarctic ◽

Global Sea Level ◽

The Antarctic

The Antarctic Ice Sheet stores water equivalent to 58 m in global sea-level rise. We show in simulations using the Parallel Ice Sheet Model that burning the currently attainable fossil fuel resources is sufficient to eliminate the ice sheet. With cumulative fossil fuel emissions of 10,000 gigatonnes of carbon (GtC), Antarctica is projected to become almost ice-free with an average contribution to sea-level rise exceeding 3 m per century during the first millennium. Consistent with recent observations and simulations, the West Antarctic Ice Sheet becomes unstable with 600 to 800 GtC of additional carbon emissions. Beyond this additional carbon release, the destabilization of ice basins in both West and East Antarctica results in a threshold increase in global sea level. Unabated carbon emissions thus threaten the Antarctic Ice Sheet in its entirety with associated sea-level rise that far exceeds that of all other possible sources.

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An evaluation of the surface climatology over the Totten region (Antarctica) using COSMO-CLM2

10.5194/egusphere-egu2020-5211 ◽

2020 ◽

Author(s):

Samuel Helsen ◽

Sam Vanden Broucke ◽

Alexandra Gossart ◽

Niels Souverijns ◽

Nicole van Lipzig

Keyword(s):

High Resolution ◽

Sea Level Rise ◽

Sea Level ◽

Climate Models ◽

Climate Model ◽

Ice Sheet ◽

Ocean Model ◽

Precipitation Pattern ◽

Outlet Glacier ◽

The Antarctic

The Totten glacier is a highly dynamic outlet glacier, situated in E-Antarctica, that contains a potential sea level rise of about 3.5 meters. During recent years, this area has been influenced by sub-shelf intrusion of warm ocean currents, contributing to higher basal melt rates. Moreover, most of the ice over this area is grounded below sea level, which makes the ice shelf potentially vulnerable to the marine ice sheet instability mechanism. It is expected that, as a result of climate change, the latter mechanisms may contribute to significant ice losses in this region within the next decades, thereby contributing to future sea level rise. Up to now, most studies have been focusing on sub-shelf melt rates and the influence of the ocean, with much less attention for atmospheric processes (often ignored), which also play a key-role in determining the climatic conditions over this region. For example: surface melt is important because it contributes to hydrofracturing, a process that may lead to ice cliff instabilities. Also precipitation is an important atmospheric process, since it determines the input of mass to the ice sheet and contributes directly to the surface mass balance. In order to perform detailed studies on these processes, we need a well-evaluated climate model that represents all these processes well. Recently, the COSMO-CLM2 (CCLM2) model was adapted to the climatological conditions over Antarctica. The model was evaluated by comparing a 30 year Antarctic-wide hindcast run (1986-2016) at 25 km resolution with meteorological observational products (Souverijns et al., 2019). It was shown that the model performance is comparable to other state-of-the-art regional climate models over the Antarctic region. We now applied the CCLM2 model in a regional configuration over the Totten glacier area (E-Antarctica) at 5 km resolution and evaluated its performance over this region by comparing it to climatological observations from different stations. We show that the performance for temperature in the high resolution run is comparable to the performance of the Antarctic-wide run. Precipitation is, however, overestimated in the high-resolution run, especially over dome structures (Law-Dome). Therefore, we applied an orographic smoothening, which clearly improves the precipitation pattern with respect to observations. Wind speed is overestimated in some places, which is solved by increasing the surface roughness. This research frames in the context of the PARAMOUR project. Within PARAMOUR, CCLM2 is currently being coupled to an ocean model (NEMO) and an ice sheet model (f.ETISh/BISICLES) in order to understand decadal predictability over this region.

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Future sea-level rise from tidewater and ice-shelf tributary glaciers of the Antarctic Peninsula

Earth and Planetary Science Letters ◽

10.1016/j.epsl.2016.07.054 ◽

2016 ◽

Vol 453 ◽

pp. 161-170 ◽

Cited By ~ 3

Author(s):

Clemens Schannwell ◽

Nicholas E. Barrand ◽

Valentina Radić

Keyword(s):

Sea Level Rise ◽

Sea Level ◽

Antarctic Peninsula ◽

Ice Shelf ◽

The Antarctic

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Semi-equilibrated global sea-level change projections for the next 10 000 years

Earth System Dynamics ◽

10.5194/esd-11-953-2020 ◽

2020 ◽

Vol 11 (4) ◽

pp. 953-976

Author(s):

Jonas Van Breedam ◽

Heiko Goelzer ◽

Philippe Huybrechts

Keyword(s):

Sea Level Rise ◽

Sea Level ◽

Ice Sheet ◽

Greenland Ice Sheet ◽

Sea Level Change ◽

Strong Increase ◽

Antarctic Ice Sheet ◽

Level Change ◽

Global Sea Level ◽

The Antarctic

Abstract. The emphasis for informing policy makers on future sea-level rise has been on projections by the end of the 21st century. However, due to the long lifetime of atmospheric CO2, the thermal inertia of the climate system and the slow equilibration of the ice sheets, global sea level will continue to rise on a multi-millennial timescale even when anthropogenic CO2 emissions cease completely during the coming decades to centuries. Here we present global sea-level change projections due to the melting of land ice combined with steric sea effects during the next 10 000 years calculated in a fully interactive way with the Earth system model of intermediate complexity LOVECLIMv1.3. The greenhouse forcing is based on the Extended Concentration Pathways defined until 2300 CE with no carbon dioxide emissions thereafter, equivalent to a cumulative CO2 release of between 460 and 5300 GtC. We performed one additional experiment for the highest-forcing scenario with the inclusion of a methane emission feedback where methane is slowly released due to a strong increase in surface and oceanic temperatures. After 10 000 years, the sea-level change rate drops below 0.05 m per century and a semi-equilibrated state is reached. The Greenland ice sheet is found to nearly disappear for all forcing scenarios. The Antarctic ice sheet contributes only about 1.6 m to sea level for the lowest forcing scenario with a limited retreat of the grounding line in West Antarctica. For the higher-forcing scenarios, the marine basins of the East Antarctic Ice Sheet also become ice free, resulting in a sea-level rise of up to 27 m. The global mean sea-level change after 10 000 years ranges from 9.2 to more than 37 m. For the highest-forcing scenario, the model uncertainty does not exclude the complete melting of the Antarctic ice sheet during the next 10 000 years.

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Diverging future surface mass balance between the Antarctic ice shelves and grounded ice sheet

The Cryosphere ◽

10.5194/tc-15-1215-2021 ◽

2021 ◽

Vol 15 (3) ◽

pp. 1215-1236

Author(s):

Christoph Kittel ◽

Charles Amory ◽

Cécile Agosta ◽

Nicolas C. Jourdain ◽

Stefan Hofer ◽

...

Keyword(s):

Mass Balance ◽

Sea Level Rise ◽

Sea Level ◽

Ice Sheet ◽

Surface Mass Balance ◽

Near Surface ◽

Surface Mass ◽

Ice Shelves ◽

Run Off ◽

The Antarctic

Abstract. The future surface mass balance (SMB) will influence the ice dynamics and the contribution of the Antarctic ice sheet (AIS) to the sea level rise. Most of recent Antarctic SMB projections were based on the fifth phase of the Coupled Model Intercomparison Project (CMIP5). However, new CMIP6 results have revealed a +1.3 ∘C higher mean Antarctic near-surface temperature than in CMIP5 at the end of the 21st century, enabling estimations of future SMB in warmer climates. Here, we investigate the AIS sensitivity to different warmings with an ensemble of four simulations performed with the polar regional climate model Modèle Atmosphérique Régional (MAR) forced by two CMIP5 and two CMIP6 models over 1981–2100. Statistical extrapolation enables us to expand our results to the whole CMIP5 and CMIP6 ensembles. Our results highlight a contrasting effect on the future grounded ice sheet and the ice shelves. The SMB over grounded ice is projected to increase as a response to stronger snowfall, only partly offset by enhanced meltwater run-off. This leads to a cumulated sea-level-rise mitigation (i.e. an increase in surface mass) of the grounded Antarctic surface by 5.1 ± 1.9 cm sea level equivalent (SLE) in CMIP5-RCP8.5 (Relative Concentration Pathway 8.5) and 6.3 ± 2.0 cm SLE in CMIP6-ssp585 (Shared Socioeconomic Pathways 585). Additionally, the CMIP6 low-emission ssp126 and intermediate-emission ssp245 scenarios project a stabilized surface mass gain, resulting in a lower mitigation to sea level rise than in ssp585. Over the ice shelves, the strong run-off increase associated with higher temperature is projected to decrease the SMB (more strongly in CMIP6-ssp585 compared to CMIP5-RCP8.5). Ice shelves are however predicted to have a close-to-present-equilibrium stable SMB under CMIP6 ssp126 and ssp245 scenarios. Future uncertainties are mainly due to the sensitivity to anthropogenic forcing and the timing of the projected warming. While ice shelves should remain at a close-to-equilibrium stable SMB under the Paris Agreement, MAR projects strong SMB decrease for an Antarctic near-surface warming above +2.5 ∘C compared to 1981–2010 mean temperature, limiting the warming range before potential irreversible damages on the ice shelves. Finally, our results reveal the existence of a potential threshold (+7.5 ∘C) that leads to a lower grounded-SMB increase. This however has to be confirmed in following studies using more extreme or longer future scenarios.

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Uncertainty quantification of the multi-centennial response of the Antarctic Ice Sheet to climate change

10.5194/tc-2018-220 ◽

2018 ◽

Author(s):

Kevin Bulthuis ◽

Maarten Arnst ◽

Sainan Sun ◽

Frank Pattyn

Keyword(s):

Climate Change ◽

Sea Level Rise ◽

Sea Level ◽

Ice Sheet ◽

Parametric Uncertainty ◽

Antarctic Ice Sheet ◽

West Antarctic Ice Sheet ◽

Sources Of Uncertainty ◽

West Antarctic ◽

The Antarctic

Abstract. Ice loss from the Antarctic ice sheet (AIS) is expected to become the major contributor to sea-level rise in the next centuries. Projections of the AIS response to climate change based on numerical ice-sheet models remain challenging to establish due to the complexity of physical processes involved in ice-sheet dynamics, including instability mechanisms that can destabilise marine sectors with retrograde slopes. Moreover, uncertainties in ice-sheet models limit the ability to provide accurate sea-level rise projections. Here, we apply probabilistic methods to a hybrid ice-sheet model to investigate the influence of several sources of uncertainty, namely sources of uncertainty in atmospheric forcing, basal sliding, grounding-line flux parameterisation, calving, sub-shelf melting, ice-shelf rheology and bedrock relaxation, on the continental response of the Antarctic ice sheet to climate change over the next millennium. We provide probabilistic projections of sea-level rise and grounding-line retreat and we carry out stochastic sensitivity analyses to determine the most influential sources of uncertainty. We find that all sources of uncertainty, except perhaps the bedrock relaxation times, contribute to the uncertainty in the projections. We show that the sensitivity of the projections to uncertainties increases and the contribution of the uncertainty in sub-shelf melting to the uncertainty in the projections becomes more and more dominant as the scenario gets warmer. We show that the significance of the AIS contribution to sea-level rise is controlled by marine ice-sheet instability (MISI) in marine basins, with the biggest contribution stemming from the more vulnerable West Antarctic ice sheet. We find that, irrespectively of parametric uncertainty, the strongly mitigated RCP 2.6 scenario prevents the collapse of the West Antarctic ice sheet, that in both RCP 4.5 and RCP 6.0 scenarios the occurrence of MISI in marine basins is more sensitive to parametric uncertainty and that, almost irrespectively of parametric uncertainty, RCP 8.5 triggers the collapse of the West Antarctic ice sheet.

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