Slowdown in Antarctic mass loss from solid Earth and sea-level feedbacks

Larour, Eric; Seroussi, Hélène; Adhikari, Surendra; Ivins, E. R.; Caron, Lambert; Morlighem, Mathieu; Schlegel, Nicole‐Jeanne

doi:10.1126/science.aav7908

Cited by 79 publications

(119 citation statements)

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“…These findings are consistent with previous theoretical (Gomez et al, 2015) and observational (Barletta et al, 2018; Kingslake et al, 2018) work, although on shorter timescales owing to the regionally low‐viscosity and high‐resolution coupling used here. Considering only losses at Pine Island, other components of GIA, such as perturbations to the geoid and existing uplift from previous mass loss, have a further (although smaller) impact (Gomez et al, 2010; Gomez et al, 2015; Larour et al, 2019) on retreat. This work highlights the importance of coupling GIA‐related deformations when predicting the grounding line evolution of marine ice sheets, particularly in regions characterized by large lateral heterogeneities, and the requirement of high‐resolution, local constraints on mantle rheology and bedrock topography over time.…”

Section: Resultsmentioning

confidence: 99%

“…We have demonstrated how the viscosity of the mantle and elastic thickness of the lithosphere mediate this feedback (Figure 2). We have omitted other components of the solid Earth response that could affect the dynamics of the grounding line, like the combined gravitational effects of ice mass loss and mantle displacement (Gomez et al, 2010; Gomez et al, 2015; Larour et al, 2019) and the ongoing uplift from older mass loss (Barletta et al, 2018). We show below that the effect of these are smaller in magnitude than the viscoelastic uplift.…”

Section: Discussionmentioning

confidence: 99%

“…Gomez et al (2015) showed that the total perturbation of the geoid can be almost as stabilizing as the deformable solid surface for simulations of the whole Antarctic continent over thousands of years. Larour et al (2019), on the other hand, demonstrated that perturbations to the geoid were smaller than purely elastic effects for continent‐scale simulations on timescales of several hundred years. We show that both elastic and geoid effects are smaller than rapid viscoelastic uplift.…”

Section: Discussionmentioning

confidence: 99%

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Rapid Viscoelastic Deformation Slows Marine Ice Sheet Instability at Pine Island Glacier

Kachuck

Martín

Bassis

et al. 2020

Geophysical Research Letters

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The ice sheets of the Amundsen Sea Embayment (ASE) are vulnerable to the marine ice sheet instability (MISI), which could cause irreversible collapse and raise sea levels by over a meter. The uncertain timing and scale of this collapse depend on the complex interaction between ice, ocean, and bedrock dynamics. The mantle beneath the ASE is likely less viscous (∼10 18 Pa s) than the Earth's average mantle (∼10 21 Pa s). Here we show that an effective equilibrium between Pine Island Glacier's retreat and the response of a weak viscoelastic mantle can reduce ice mass lost by almost 30% over 150 years. Other components of solid Earth response-purely elastic deformations and geoid perturbations-provide less stability than the viscoelastic response alone. Uncertainties in mantle rheology, topography, and basal melt affect how much stability we expect, if any. Our study indicates the importance of considering viscoelastic uplift during the rapid retreat associated with MISI.Plain Language Summary Portions of the West Antarctic Ice Sheet are vulnerable to an instability that could lead to rapid ice sheet collapse, significantly raising sea levels, but the timing and rates of collapse are highly uncertain. In response to such a large-scale loss of overlying ice, viscoelastically deforming mantle material uplifts the surface, alleviating some drivers of unstable ice sheet retreat. While previous studies have focused on the effects mantle deformation has on continental ice dynamics over centuries to millennia, recent seismic observations suggest that the mantle beneath West Antarctica is hot and weak, potentially affecting local glacial dynamics over timescales as short as decades. To measure the importance of viscoelastic uplift in stabilizing grounding line retreat, we coupled a high-resolution ice flow model to a viscoelastically deforming mantle. We find that rapid viscoelastic uplift can reduce the total volume of ice lost over 150 years by 30%, or 18 mm of equivalent sea level rise, making it an essential process to consider when using models to project the future evolution of marine-based ice retreat.

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Section: Resultsmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

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Rapid Viscoelastic Deformation Slows Marine Ice Sheet Instability at Pine Island Glacier

Kachuck

Martín

Bassis

et al. 2020

Geophysical Research Letters

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“…Glaciol. ), calving(Benn et al, 2017) or interaction with Solid Earth(Gomez et al, 2015;Larour et al, 2019).The analysis of the simulations conducted here is presented relative to the ctrl_proj, and current trends in Antarctic mass loss are added afterwards. It was decided that using results of ice flow simulations directly, without subtracting the trend from 515 20 https://doi.org/10.5194/tc-2019-324 Preprint.…”

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confidence: 99%

ISMIP6 Antarctica: a multi-model ensemble of the Antarctic ice sheet evolution over the 21st century

Seroussi¹,

Goelzer²,

Morlighem³

2020

Preprint

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Ice flow models of the Antarctic ice sheet are commonly used to simulate its future evolution in response to different climate scenarios and inform on the mass loss that would contribute to future sea level rise. However, there is currently no consensus on estimated the future mass balance of the ice sheet, primarily because of differences in the representation of physical processes and the forcings employed. This study presents results from 18 simulations from 15 international groups focusing on the evolution of the Antarctic ice sheet during the period 2015-2100, forced with different scenarios from the Cou-5 pled Model Intercomparison Project Phase 5 (CMIP5) representative of the spread in climate model results. The contribution of the Antarctic ice sheet in response to increased warming during this period varies between -7.8 and 30.0 cm of Sea Level Equivalent (SLE). The evolution of the West Antarctic Ice Sheet varies widely among models, with an overall mass loss up to 21.0 cm SLE in response to changes in oceanic conditions. East Antarctica mass change varies between -6.5 and 16.5 cm SLE, with a significant increase in surface mass balance outweighing the increased ice discharge under most RCP 8.5 scenario 10 forcings. The inclusion of ice shelf collapse, here assumed to be caused by large amounts of liquid water ponding at the surface of ice shelves, yields an additional mass loss of 8 mm compared to simulations without ice shelf collapse. The largest sources of uncertainty come from the ocean-induced melt rates, the calibration of these melt rates based on oceanic conditions taken outside of ice shelf cavities and the ice sheet dynamic response to these oceanic changes. Results under RCP 2.6 scenario based on two CMIP5 AOGCMs show an overall mass loss of 10 mm SLE compared to simulations done under present-day 15 conditions, with limited mass gain in East Antarctica.

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“…Rather than make quantitative predictions (which remain elusive because of model and forcing uncertainties), our main intent is to explore parameter space, taking advantage of the ISMIP6 framework to build on previous multi-century Antarctic simulations (e.g., Pollard and Deconto, 2009;Cornford et al, 2015;Pollard and DeConto, 2016;Larour et al, 2019). The ice-sheet physics is conventional in the sense that it includes well-understood retreat mechanisms such as MISI, but not hydrofracture or cliff collapse (Pollard et al, 2015;Pollard and DeConto, 2016).…”

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confidence: 99%

ISMIP6 projections of ocean-forced Antarctic Ice Sheet evolution using the Community Ice Sheet Model

Lipscomb

Leguy

Jourdain

et al. 2020

Preprint

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Abstract. The future retreat rate for marine-based regions of the Antarctic Ice Sheet is one of the largest uncertainties in sea-level projections. The Ice Sheet Model Intercomparison Project for CMIP6 (ISMIP6) aims to improve projections and quantify uncertainties by running an ensemble of ice sheet models with atmosphere and ocean forcing derived from global climate models. Here, ISMIP6 projections of ocean-forced Antarctic Ice Sheet evolution are illustrated using the Community Ice Sheet Model (CISM). Using multiple combinations of sub-ice-shelf melt parameterizations and calibrations, CISM is spun up to steady state over many millennia. During the spin-up, basal friction parameters and basin-scale thermal forcing corrections are adjusted to nudge the ice thickness toward observed values. The model is then run forward for 500 years, applying ocean thermal forcing anomalies from six climate models. In all simulations, the ocean forcing triggers long-term retreat of the West Antarctic Ice Sheet, including the Amundsen, Filchner-Ronne, and Ross Basins. Mass loss accelerates late in the 21st century and rises steadily over the next several centuries without leveling off. The resulting ocean-forced SLR at year 2500 varies from about 10 cm to nearly 2 m, depending on the melt scheme and model forcing. Relatively little ice loss is simulated in East Antarctica. Large uncertainties remain, as a result of parameterized basal melt rates, missing ocean and ice sheet physics, and the lack of ice–ocean coupling.

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Slowdown in Antarctic mass loss from solid Earth and sea-level feedbacks

Cited by 79 publications

References 47 publications

Rapid Viscoelastic Deformation Slows Marine Ice Sheet Instability at Pine Island Glacier

Rapid Viscoelastic Deformation Slows Marine Ice Sheet Instability at Pine Island Glacier

ISMIP6 Antarctica: a multi-model ensemble of the Antarctic ice sheet evolution over the 21st century

ISMIP6 projections of ocean-forced Antarctic Ice Sheet evolution using the Community Ice Sheet Model

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