C053-05
Two decades of dynamic changes on the Thwaites Eastern Ice Shelf

Tuesday, 15 December 2020: 04:16
Virtual
Karen E Alley, University of Manitoba, Environment and Geography, Winnipeg, MB, Canada, Christian Thomas Wild, Oregon State University, Corvalis, OR, United States, Luc Girod, University of Oslo, Department of Geosciences, Oslo, Norway, Adrian J Luckman, Swansea University, Glaciology Group, Swansea, United Kingdom, Sarah F Child, University of Colorado at Boulder, Boulder, CO, United States, Cyrus Hulen, College of Wooster, Wooster, OH, United States, Erin Pettit, Oregon State, Corvallis, Oregon, United States, Atsuhiro Muto, Temple University, Department of Earth and Environmental Science, Philadelphia, PA, United States, Ted A Scambos, University of Colorado, Boulder, Boulder, CO, United States, Martin Truffer, University of Alaska Fairbanks, Geophysical Institute, Fairbanks, AK, United States, Bruce Wallin, National Snow and Ice Data Center, Boulder, CO, United States and Marin J Klinger, University of Colorado, Boulder, National Snow and Ice Data Center, Boulder, CO, United States
Recorded Presentation
Abstract:
The floating portion of Thwaites Glacier comprises a fast-flowing western ice tongue, which has largely disintegrated in recent years, and a relatively slow-flowing eastern ice shelf that has remained fundamentally intact. The Thwaites Eastern Ice Shelf (TEIS) buttresses the grounded portion of Thwaites Glacier through contact with a pinning point at its seaward limit, which suggests that future loss of this ice shelf will promote further acceleration of Thwaites Glacier. Understanding the dynamic controls and structural integrity of this ice shelf is therefore important to estimating future sea-level contributions. We present a ~20-year record of horizontal and vertical changes on the TEIS that reveals the dynamic controls governing the ice shelf’s past and present behavior. We derived velocities from MODIS and Landsat imagery using feature tracking, and from Sentinel-1 radar using speckle tracking. We also calculated strain rates from the combined velocity record on annual and seasonal timescales. Patterns of ice-shelf thinning were revealed by differencing two ASTER DEMs, one from 2004 and one from 2020, which were vertically referenced using contemporary ICESat and ICESat-2 data. Results show that velocity patterns on the TEIS during this record have been strongly controlled by the strength of the shear margin with the western ice tongue. When the shear margin was strong and intact, the TEIS accelerated significantly to average speeds of approximately 2 km/year as the western ice tongue dragged it forward, and a swarm of crevasses formed at the grounding line in response to the enhanced strain. Since the disintegration of the western ice tongue, the TEIS has developed independent flow patterns, including slower speeds (<1 km/year) and the rotation of ice flow on the western edge toward the open ocean previously occupied by the western ice tongue. This change in flow direction, coupled with sustained thinning, has led to the formation of large mid-shelf rifts that may contribute to future shelf-wide destabilization.
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