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- Title
Comparing Glacial‐Geological Evidence and Model Simulations of Ice Sheet Change since the Last Glacial Period in the Amundsen Sea Sector of Antarctica.
- Authors
Johnson, Joanne S.; Pollard, David; Whitehouse, Pippa L.; Roberts, Stephen J.; Rood, Dylan H.; Schaefer, Joerg M.
- Abstract
Since the Last Glacial Maximum ∼20,000 years ago, the Antarctic Ice Sheet has undergone extensive changes, resulting in a much smaller present‐day configuration. Improving our understanding of basic physical processes that played important roles during that retreat is critical to providing more robust model projections of future retreat and sea‐level rise. Here, a limited‐area nested ice sheet model was applied to the last deglacial retreat of the West Antarctic Ice Sheet in the Amundsen Sea Embayment (ASE), at 5 km resolution. The ice sheet response to climate and sea‐level forcing was examined at two sites along the flowlines of Pine Island Glacier and Pope Glacier, close to the Hudson Mountains and Mount Murphy respectively, and the simulated responses compared with ice sheet thinning histories derived from glacial‐geological data. The sensitivity of results to selected model parameters was also assessed. The model simulations predict a broadly similar response to ocean forcing in both the central and eastern ASE, with an initial rapid phase of thinning followed by a slower phase to the modern configuration. Although there is a mismatch of up to 5,000 years between the timing of simulated and observed thinning, the modeling suggests that the upstream geological records of ice surface elevation change reflect a response to retreat near the grounding line. The model‐data mismatch could potentially be improved by accounting for regional variations in mantle viscosity, sea‐surface heights and basal sliding properties across the continental shelf. Plain Language Summary: During the last glacial period approximately 20,000 years ago, the West Antarctic Ice Sheet was much larger than today. Since then, it has undergone extensive changes such as retreat and thinning of its glaciers, and currently dominates the contribution to global sea‐level rise from Antarctica. Glacial‐geological studies undertaken in two mountain ranges in the region (the Hudson Mountains and Mt Murphy, close to Pine Island Glacier and Pope Glacier) provided records of the magnitude and speed of those changes. Here we compare those records with model simulations that predict response of the ice sheet to different forcing mechanisms (climate and sea‐level) over the past 20,000 years. We find that the model predicts a similar response to forcing at both study sites, with initially fast thinning followed by a slower phase as the ice sheet shrinks to its modern shape and size. The similarity in behavior at both sites may be due to similar ocean forcing mechanisms affecting both glaciers. When we compare the model simulations with geological records of ice sheet change, we find a mismatch of up to 5,000 years. Improving how ice‐Earth interactions are represented in the model could potentially resolve this mismatch. Key Points: A nested ice sheet model was applied to the last deglacial retreat in the Amundsen Sea sector, Antarctica. Model outputs were compared with ice thinning historySimilar response to forcing across Amundsen Sea Embayment, possibly resulting from similar (ocean) forcing mechanisms in early HoloceneImproved representation of regionally varying Earth‒ice‒sea‐level interactions may resolve model‐data mismatch in timing of ice thinning
- Subjects
AMUNDSEN Sea (Antarctica); GLACIOLOGY; GLACIERS; ICE sheet thawing; GLACIAL melting
- Publication
Journal of Geophysical Research. Earth Surface, 2021, Vol 126, Issue 6, p1
- ISSN
2169-9003
- Publication type
Article
- DOI
10.1029/2020JF005827