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On the relative importance of offshelf/onshelf drivers of variability in mCDW inventory on the Amundsen Shelf, Antarctica
St-Laurent, Pierre Stammerjohn, S. E. Maksym, T. Sherrell, R. M.
St-Laurent, Pierre
Stammerjohn, S. E.
Maksym, T.
Sherrell, R. M.
Abstract
Ice shelves in the Amundsen Sea (west Antarctica) are melting rapidly and may raise global sea levels substantially over the coming century through reduced buttressing. The high basal melt rates are associated with the presence of warm modified Circumpolar Deep Water (mCDW) that intrudes across the continental shelf and melts the floating portion of the ice sheet from its base near the grounding zone. How much mCDW is present on the continental shelf (its volume inventory) is thus thought to be a key proxy for the year-to-year variability in ice shelf melt rates. Over the past decade, the literature has linked this year-to-year variability to processes acting on the continental shelf (“onshelf”) as well as processes acting offshelf (or at the shelf break), but their relative influence remains unclear. Hydrographic surveys from 2007-2018 in the Dotson-Getz Trough reveal a smooth high/low/high pattern in annual mCDW inventories that could reflect processes acting offshelf, onshelf, or both. In the present work, a regional 3D sea ice-ice shelves-ocean model simulates the period 2006-2022 while using historical reanalysis meteorology but the same oceanic conditions offshelf throughout this period. The simulation effectively evaluates how much of the high/low/high pattern can be reproduced in absence of offshelf variability. Results indicate that the observed pattern is reproduced in the basal melt of Pine Island, Thwaites, Crosson, and Dotson ice shelves. The “low” represents a decrease of as much as ~25 Gt/yr for some of these ice shelves. While the “low” becomes apparent as early as summer 2012 for some ice shelves, the timing of the recovery varies. Ice shelves positioned in the east are the first ones to recover (circa mid-2016) and this recovery extends to Crosson and Dotson ~2 years later, reminiscent of the pathway of mCDW inside the Eastern Trough. The simulation supports the view that dynamical processes acting on the shelf (e.g. local Ekman pumping) can explain a substantial portion of the observed year-to-year variability.
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2022-12-12
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Aquatic Health Sciences
Aquatic Health Sciences Presentations, Ice shelves, Amundsen Sea, Ice sheets, sea ice, Antarctica, modeling
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Virginia Institute of Marine Science
DOI
https://doi.org/10.25773/chnp-gd30