Coastal Antarctica’s vast, floating ice shelves buttress against glacial flow of the Antarctic ice sheet into the ocean. However, relatively warm ocean waters are rapidly melting some ice shelves from beneath, leading to ice sheet retreat. This submarine melting is important particularly in West Antarctica, where the inland-deepening bedrock means this retreat could begin to accelerate, contributing greatly to sea level rise. New research by Goldberg et al. investigates a West Antarctic glacier system, pinpointing missing knowledge vital for predicting how shelf melt will affect the ice sheet.
Mathematical models of ice shelf melt rates are essential to predict resulting ice sheet loss. However, it has been unclear how accurately ice shelf models capture different melt rates in different shelf locations and how accurate these models need to be to make reliable ice sheet predictions.
To address these issues, the authors focused on West Antarctica’s Crosson and Dotson ice shelves, which, like several other ice shelves, are thinning from exposure to relatively warm Circumpolar Deep Water. This thinning may underpin decreased buttressing of three glaciers—Smith, Pope, and Kohler—that flow from the Antarctic ice sheet into the shelves.
The researchers used the Massachusetts Institute of Technology (MIT) General Circulation Model (MITgcm) to model melt rates beneath Crosson and Dotson, exploring several different mathematical representations of ocean physics and of the geometry of the cavities beneath the shelves where melting occurs. They also calculated real-world shelf melt rates using data from the satellites CryoSat-2 and Sentinel-1.
The analysis showed that melt rates were highly variable between different underwater locations beneath the two shelves. Comparison of the model outputs to the satellite observations revealed key factors necessary for accurate modeling of these variations, including improved bathymetric data and better knowledge of ocean flow next to the ice.
Next, the scientists used MITgcm’s STREAMICE feature to model how varying ice shelf melt rates affect ice flow for the Smith, Pope, and Kohler glaciers. They found that capturing different melt rates in different locations is important for accurately modeling glacier response but appears to be more important for some locations than others. Critical underwater melt locations include grounding lines, where land-bound glaciers transition to floating ice shelves, and shear margins, high-friction boundaries between shelves.
These findings suggest that improved modeling and observations of ice-ocean dynamics at grounding lines and shear margins are needed to accurately predict how climate change will affect ice shelves and ice sheets. (Geophysical Research Letters, https://doi.org/10.1029/2018GL080383, 2019)
—Sarah Stanley, Freelance Writer
from Eos https://eos.org/research-spotlights/whats-missing-from-antarctic-ice-sheet-loss-predictions?utm_source=rss&utm_medium=rss&utm_content=whats-missing-from-antarctic-ice-sheet-loss-predictions
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