West Antarctica, the sea-level controlled marine instability: Past and future

Abstract. Pine Island Glacier, a major contributor to sea level rise in West Antarctica, has been undergoing significant changes over the last few decades. Here, we employ a three-dimensional, higher-order model to simulate its evolution over the next 50 yr in response to changes in its surface mass balance, the position of its calving front and ocean-induced ice shelf melting. Simulations show that the largest climatic impact on ice dynamics is the rate of ice shelf melting, which rapidly affects the glacier speed over several hundreds of kilometers upstream of the grounding line. Our simulations show that the speedup observed in the 1990s and 2000s is consistent with an increase in sub-ice-shelf melting. According to our modeling results, even if the grounding line stabilizes for a few decades, we find that the glacier reaction can continue for several decades longer. Furthermore, Pine Island Glacier will continue to change rapidly over the coming decades and remain a major contributor to sea level rise, even if ocean-induced melting is reduced.

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Reassessing the Contribution of West Antarctica to Last Interglacial Sea Level in Light of 3D Mantle Viscosity Structure

10.5194/egusphere-egu21-13786 ◽

2021 ◽

Author(s):

Linda Pan ◽

Evelyn M. Powell ◽

Konstantin Latychev ◽

Jerry X. Mitrovica ◽

Jessica R. Creveling ◽

...

Keyword(s):

Sea Level ◽

Complex Structure ◽

Ice Sheet ◽

West Antarctica ◽

Last Interglacial ◽

West Antarctic Ice Sheet ◽

West Antarctic ◽

Low Viscosity ◽

Global Mean Sea Level ◽

Warming World

Studies of peak global mean sea level (GMSL) during the Last Interglacial (LIG; 130-116 ka) commonly cite values ranging from ~2-5 m for the maximum contribution from grounded, marine-based sectors of the West Antarctic Ice Sheet (WAIS). However, this estimate neglects viscoelastic crustal uplift and the associated meltwater flux out of marine sectors as they are exposed, a contribution considered to be small and slowly-accumulating. This assumption should be revisited, as a range of evidence indicates that West Antarctica is underlain by shallow mantle of anomalously low viscosity. By incorporating this complex structure into a gravitationally self-consistent sea-level calculation, we find that GMSL differs substantially from previous estimates. Our results indicate that these estimates thus require a reassessment of the contribution to GMSL rise from WAIS collapse, as will ice sheet models that do not account for the uplift mechanism. This conclusion has important implications for the sea level budget not only during the LIG, but also for all previous interglacials and projections of GMSL change in the future warming world. &#160;

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Damage accelerates ice shelf instability and mass loss in Amundsen Sea Embayment

Proceedings of the National Academy of Sciences ◽

10.1073/pnas.1912890117 ◽

2020 ◽

Vol 117 (40) ◽

pp. 24735-24741 ◽

Cited By ~ 1

Author(s):

Stef Lhermitte ◽

Sainan Sun ◽

Christopher Shuman ◽

Bert Wouters ◽

Frank Pattyn ◽

...

Keyword(s):

Sea Level ◽

Rapid Development ◽

Shear Zones ◽

West Antarctica ◽

Ice Shelf ◽

Damage Development ◽

Amundsen Sea ◽

Ice Shelves ◽

Grounding Line ◽

Global Sea Level

Pine Island Glacier and Thwaites Glacier in the Amundsen Sea Embayment are among the fastest changing outlet glaciers in West Antarctica with large consequences for global sea level. Yet, assessing how much and how fast both glaciers will weaken if these changes continue remains a major uncertainty as many of the processes that control their ice shelf weakening and grounding line retreat are not well understood. Here, we combine multisource satellite imagery with modeling to uncover the rapid development of damage areas in the shear zones of Pine Island and Thwaites ice shelves. These damage areas consist of highly crevassed areas and open fractures and are first signs that the shear zones of both ice shelves have structurally weakened over the past decade. Idealized model results reveal moreover that the damage initiates a feedback process where initial ice shelf weakening triggers the development of damage in their shear zones, which results in further speedup, shearing, and weakening, hence promoting additional damage development. This damage feedback potentially preconditions these ice shelves for disintegration and enhances grounding line retreat. The results of this study suggest that damage feedback processes are key to future ice shelf stability, grounding line retreat, and sea level contributions from Antarctica. Moreover, they underline the need for incorporating these feedback processes, which are currently not accounted for in most ice sheet models, to improve sea level rise projections.

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Increased estimate of sea-level rise contribution from West Antarctica

ECOS ◽

10.1071/ec14006 ◽

2014 ◽

Keyword(s):

Sea Level Rise ◽

Sea Level ◽

West Antarctica

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Retreat of Thwaites Glacier, West Antarctica, over the next 100 years using various ice flow models, ice shelf melt scenarios and basal friction laws

The Cryosphere ◽

10.5194/tc-12-3861-2018 ◽

2018 ◽

Vol 12 (12) ◽

pp. 3861-3876 ◽

Cited By ~ 12

Author(s):

Hongju Yu ◽

Eric Rignot ◽

Helene Seroussi ◽

Mathieu Morlighem

Keyword(s):

Sea Level ◽

Initial Conditions ◽

Numerical Models ◽

West Antarctica ◽

Ice Shelf ◽

Flow Models ◽

Friction Laws ◽

Basal Friction ◽

Grounding Line ◽

Western Side

Abstract. Thwaites Glacier (TG), West Antarctica, has experienced rapid, potentially irreversible grounding line retreat and mass loss in response to enhanced ice shelf melting. Results from recent numerical models suggest a large spread in the evolution of the glacier in the coming decades to a century. It is therefore important to investigate how different approximations of the ice stress balance, parameterizations of basal friction and ice shelf melt parameterizations may affect projections. Here, we simulate the evolution of TG using ice sheet models of varying levels of complexity, different basal friction laws and ice shelf melt to quantify their effect on the projections. We find that the grounding line retreat and its sensitivity to ice shelf melt are enhanced when a full-Stokes model is used, a Budd friction is used and ice shelf melt is applied on partially floating elements. Initial conditions also impact the model results. Yet, all simulations suggest a rapid, sustained retreat of the glacier along the same preferred pathway. The fastest retreat rate occurs on the eastern side of the glacier, and the slowest retreat occurs across a subglacial ridge on the western side. All the simulations indicate that TG will undergo an accelerated retreat once the glacier retreats past the western subglacial ridge. Combining all the simulations, we find that the uncertainty of the projections is small in the first 30 years, with a cumulative contribution to sea level rise of 5 mm, similar to the current rate. After 30 years, the contribution to sea level depends on the model configurations, with differences up to 300 % over the next 100 years, ranging from 14 to 42 mm.

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Major increases projected in extreme surface melt events in Antarctica, even under a moderate emission scenario

10.5194/egusphere-egu2020-21267 ◽

2020 ◽

Author(s):

Sarah Feron ◽

Raul Cordero

Keyword(s):

Sea Level ◽

Antarctic Peninsula ◽

Climate Models ◽

Emission Scenario ◽

Global Climate ◽

Global Climate Models ◽

Reference Period ◽

West Antarctica ◽

Surface Melt ◽

The Antarctic

Surface Melt (SM) is one of the factors that contribute to sea level rise; surface&#160;meltwater draining through the ice and beneath&#160;Antarctic&#160;glaciers may cause acceleration in their flow towards the sea. Changes in the frequency of relatively warm days (including heatwaves) can substantially alter the SM variability, thus leading to extreme melting events.&#160;By using simulations from 13 Global Climate Models (GCMs) and according to a moderate representative concentration pathways (RCP4.5), here we show that the frequency of extreme SM events (SM90; according to the 90th percentile over the reference period 1961-1990) may significantly increase in coastal areas of West Antarctica; in particular in the Antarctic Peninsula. By the end of the century SM90 estimates are expected to increase from currently 0.10 kg/m2/day to about 0.45 kg/m2/day in the Antarctic Peninsula. Increments in SM90 estimates are not just driven by changes in the average SM, but also by the variability in SM. The latter is expected to increase by around 50% in the Antarctic Peninsula.

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Collapse of the West Antarctic Ice Sheet after local destabilization of the Amundsen Basin

Proceedings of the National Academy of Sciences ◽

10.1073/pnas.1512482112 ◽

2015 ◽

Vol 112 (46) ◽

pp. 14191-14196 ◽

Cited By ~ 62

Author(s):

Johannes Feldmann ◽

Anders Levermann

Keyword(s):

Sea Level Rise ◽

Sea Level ◽

Ice Sheet ◽

Horizontal Resolution ◽

West Antarctica ◽

Amundsen Sea ◽

Ice Dynamics ◽

Antarctic Ice Sheet ◽

Topographic Features ◽

Global Sea Level

The future evolution of the Antarctic Ice Sheet represents the largest uncertainty in sea-level projections of this and upcoming centuries. Recently, satellite observations and high-resolution simulations have suggested the initiation of an ice-sheet instability in the Amundsen Sea sector of West Antarctica, caused by the last decades’ enhanced basal ice-shelf melting. Whether this localized destabilization will yield a full discharge of marine ice from West Antarctica, associated with a global sea-level rise of more than 3 m, or whether the ice loss is limited by ice dynamics and topographic features, is unclear. Here we show that in the Parallel Ice Sheet Model, a local destabilization causes a complete disintegration of the marine ice in West Antarctica. In our simulations, at 5-km horizontal resolution, the region disequilibrates after 60 y of currently observed melt rates. Thereafter, the marine ice-sheet instability fully unfolds and is not halted by topographic features. In fact, the ice loss in Amundsen Sea sector shifts the catchment's ice divide toward the Filchner–Ronne and Ross ice shelves, which initiates grounding-line retreat there. Our simulations suggest that if a destabilization of Amundsen Sea sector has indeed been initiated, Antarctica will irrevocably contribute at least 3 m to global sea-level rise during the coming centuries to millennia.

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Changes in ice dynamics and mass balance of the Antarctic ice sheet

Philosophical Transactions of The Royal Society A Mathematical Physical and Engineering Sciences ◽

10.1098/rsta.2006.1793 ◽

2006 ◽

Vol 364 (1844) ◽

pp. 1637-1655 ◽

Cited By ~ 77

Author(s):

Eric Rignot

Keyword(s):

Mass Balance ◽

Sea Level ◽

Ice Sheet ◽

East Antarctica ◽

West Antarctica ◽

Ice Shelf ◽

Ice Dynamics ◽

Antarctic Ice Sheet ◽

Ice Shelves ◽

The Antarctic

The concept that the Antarctic ice sheet changes with eternal slowness has been challenged by recent observations from satellites. Pronounced regional warming in the Antarctic Peninsula triggered ice shelf collapse, which led to a 10-fold increase in glacier flow and rapid ice sheet retreat. This chain of events illustrated the vulnerability of ice shelves to climate warming and their buffering role on the mass balance of Antarctica. In West Antarctica, the Pine Island Bay sector is draining far more ice into the ocean than is stored upstream from snow accumulation. This sector could raise sea level by 1 m and trigger widespread retreat of ice in West Antarctica. Pine Island Glacier accelerated 38% since 1975, and most of the speed up took place over the last decade. Its neighbour Thwaites Glacier is widening up and may double its width when its weakened eastern ice shelf breaks up. Widespread acceleration in this sector may be caused by glacier ungrounding from ice shelf melting by an ocean that has recently warmed by 0.3 °C. In contrast, glaciers buffered from oceanic change by large ice shelves have only small contributions to sea level. In East Antarctica, many glaciers are close to a state of mass balance, but sectors grounded well below sea level, such as Cook Ice Shelf, Ninnis/Mertz, Frost and Totten glaciers, are thinning and losing mass. Hence, East Antarctica is not immune to changes.

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Stopping the Flood: Could We Use Targeted Geoengineering to Mitigate Sea Level Rise?

10.5194/tc-2018-95 ◽

2018 ◽

Cited By ~ 1

Author(s):

Michael J. Wolovick ◽

John C. Moore

Keyword(s):

Sea Level Rise ◽

Sea Level ◽

Ice Sheet ◽

Dynamic Feedback ◽

West Antarctica ◽

Ice Shelf ◽

Long Run ◽

Grounding Line ◽

Individual Source ◽

Engineering Projects

Abstract. The Marine Ice Sheet Instability (MISI) is a dynamic feedback that can cause an ice sheet to enter a runaway collapse. Thwaites Glacier, West Antarctica, is the largest individual source of future sea level rise and may have already entered the MISI. Here, we use a suite of coupled ice–ocean flowband simulations to explore whether targeted geoengineering using an artificial sill or artificial ice rises could counter a collapse. Successful interventions occur when the floating ice shelf regrounds on the pinning points, increasing buttressing and reducing ice flux across the grounding line. Regrounding is more likely with a continuous sill that is able to block warm water transport to the grounding line. The smallest design we consider is comparable in scale to existing civil engineering projects but has only a 30 % success rate, while larger designs are more effective. There are multiple possible routes forward to improve upon the designs that we considered, and with decades or more to research designs it is plausible that the scientific community could come up with a plan that was both effective and achievable. While reducing emissions remains the short-term priority for minimizing the effects of climate change, in the long run humanity may need to develop contingency plans to deal with an ice sheet collapse.

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Contrasting response of West and East Antarctic ice sheets to Glacial Isostatic Adjustment

10.5194/egusphere-egu2020-6974 ◽

2020 ◽

Author(s):

Violaine Coulon ◽

Kevin Bulthuis ◽

Sainan Sun ◽

Konstanze Haubner ◽

Frank Pattyn

Keyword(s):

Solid Earth ◽

Sea Level ◽

Ice Sheet ◽

East Antarctica ◽

Climate Forcing ◽

West Antarctica ◽

Antarctic Ice Sheet ◽

West Antarctic ◽

Earth Structures ◽

The Antarctic

The Antarctic ice sheet (AIS) lies on a solid Earth that displays large spatial variations in rheological properties, with a thin lithosphere and low-viscosity upper mantle (weak Earth structure) beneath West Antarctica and an opposing structure beneath East Antarctica. This contrast is known to have a significant impact on ice-sheet grounding-line stability. Here, we embedded a modified glacial-isostatic ELRA model within an Antarctic ice sheet model that considers a weak Earth structure for West Antarctica supplemented with an approximation of gravitationally-consistent local sea-level changes. By taking advantage of the computational efficiency of this elementary GIA model, we assess in a probabilistic way the impact of uncertainties in the Antarctic viscoelastic properties on the response of the Antarctic ice sheet to future warming by using an ensemble of 2000 Monte Carlo simulations that span a range of plausible solid Earth structures for both West and East Antarctica. We show that on multicentennial-to-millennial timescales, model projections that do not consider the dichotomy between East and West Antarctic solid Earth structures systematically overestimate the sea-level contribution from the Antarctic ice sheet because regional solid-Earth deformation plays a significant role in promoting the stability of the West Antarctic ice sheet (WAIS). However, WAIS collapse cannot be prevented under high-emissions climate scenarios. At longer timescales and under unabated climate forcing, future mass loss may be underestimated because in East Antarctica, GIA feedbacks have the potential to re-enforce the influence of the climate forcing as compared with a spatially-uniform GIA model. In this context, the AIS response might be an even larger source of uncertainty in projecting sea-level rise than previously thought, with the highest uncertainty arising from the East Antarctic ice sheet where the Aurora Basin is very GIA-dependent.

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