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

The Science

he 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.

Solid-earth feedbacks, from viscoelastic glacial isostatic adjustment (GIA) in response to unloading from ice sheet thinning, have the potential to mitigate grounding-line (GL) retreat and mass loss due to marine ice sheet instability. The mantle beneath the ASE is likely less viscous than the Earth’s average mantle. To explore this effect, we implemented full dynamic coupling of a viscoelastic solid-earth deformation model with U.S. Department of Energy (DOE)–supported BISICLES ice sheet model in the new GIANT-BISICLES model. The team found that bedrock uplift due to the viscoelastic response of a low-viscosity mantle can rapidly reduce ocean depth near the grounding line and stabilize the marine ice sheet instability over decades to centuries.

The Impact

Viscoelastic uplift on timescales similar to grounding line migration can be a leading term in determining sea level rise (SLR) rates due to MISI. The researchers demonstrate 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. The study indicates the importance of considering viscoelastic uplift during the rapid retreat associated with MISI.

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, the researchers coupled a high-resolution ice flow model to a viscoelastically deforming mantle. They found that rapid viscoelastic uplift can reduce the total volume of ice lost over 150 years by 30%, or 18 mm of equivalent SLR, making it an essential process to consider when using models to project the future evolution of marine-based ice retreat.

Principal Investigator(s)

Samuel Kachuck
University of Michigan
[email protected]

Stephen Price
Los Alamos National Laboratory
[email protected]

Funding

Support for this work was provided through the Scientific Discovery through Advanced Computing (SciDAC) program funded by the US Department of Energy (DOE), Office of Science, Biological and Environmental Research, and Advanced Scientific Computing Research Offices.

References

Kachuck, S.B., Martin, D.F., Bassis, J.N., Price, S.F. “Rapid viscoelastic deformation slows marine ice sheet instability at Pine Island Glacier.” Geophysical Research Letters 47(10), e2019GL086446 (2020). [DOI:10.1029/2019GL086446]