C052-01
Geometry of the eastern Thwaites ice shelf cavity and implications for continued grounding zone retreat

Monday, 14 December 2020: 17:30
Virtual
Kiya L Riverman1, Sridhar Anandakrishnan2, Elisabeth Rose Clyne3, Britney Schmidt4, Peter Washam4, Keith W Nicholls5, Peter E D Davis5, David Holland1, Aurora Basinski-Ferris6, Paul Anker5, James Smith5, Daniel Dichek7 and Andrew Mullen8, (1)New York University, New York, NY, United States, (2)Pennsylvania State University, University Park, PA, United States, (3)Pennsylvania State University, University Park, United States, (4)Georgia Institute of Technology, School of Earth and Atmospheric Sciences, Atlanta, GA, United States, (5)British Antarctic Survey, Cambridge, United Kingdom, (6)New York University, New York, United States, (7)Georgia Institute of Technology, Atlanta, GA, United States, (8)Scripps Institution of Oceanography, La Jolla, CA, United States
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.

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