Geometry of the eastern Thwaites ice shelf cavity and implications for continued grounding zone retreat
Abstract
The eastern Thwaites glacier ice shelf has experienced considerable grounding zone retreat since 2000, but that retreat has slowed somewhat since ~ 2009. Retreat has been largely attributed to incursions of modified Circumpolar Deep Water (mCDW), which increase sub ice-shelf melting and reduce ice-shelf buttressing. As a result, there is widespread interest in modeling the pathways of mCDW delivery to Thwaites, but bathymetric models are limited by a lack of sub ice-shelf observations. Here we present the first observations of the Thwaites eastern ice shelf cavity geometry from active source seismic surveying and ROV Icefin sonar.
The present grounding zone sits on a normal slope. Repeat seismic experiments show that grounding zone retreat rate from 2019-2020 was ~1 km/yr. We report on a significant bathymetric feature that may limit mCDW incursions to the present grounding zone and explain the relatively low (~2 m/yr) melt rates observed there. This ridge beneath the current ice shelf corresponds to the approximate position of the 2009 grounding zone, and could additionally explain the (relative) slowdown of grounding zone retreat since that time.- Publication:
-
AGU Fall Meeting Abstracts
- Pub Date:
- December 2020
- Bibcode:
- 2020AGUFMC052...01R
- Keywords:
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- 0726 Ice sheets;
- CRYOSPHERE;
- 0728 Ice shelves;
- CRYOSPHERE;
- 0776 Glaciology;
- CRYOSPHERE;
- 0793 Biogeochemistry;
- CRYOSPHERE