Ice-bed interactions and recent retreat at Thwaites Glacier
Abstract
Interactions between the ice and seafloor shape the evolution of ice shelves and leave a record of past conditions. Here we report observations collected by the Icefin underwater vehicle over a three-kilometer long region extending oceanward from the grounding line (GL) of Thwaites Glacier in January 2020, as part of the ITGC program. Bathymetric sonar, combined with ice-facing sonar and imagery of the ice base and sediment throughout this region offer new perspectives on ice-bed interactions at and directly upstream of the grounding line of the Thwaites Eastern Ice Shelf. The bed in this region slopes upward toward the grounding line and is generally characterized by along-flow ridges with ridge spacing that varies between 2-35 meters. At the grounding line, small-scale ridge topography of the bed was mimicked in the ice, creating sloped ice faces that promote enhanced melting by the warm ocean. Ice in the region also records interactions upstream, with both sediment-laden and clear basal ice, along with evidence of accretion of subglacial water upstream of the GL. Bed morphology also presents evidence for past or recent subglacial outflow via a ~4m deep, 100 m long channel cut into the sediment with segments oriented both along- and perpendicular to the ice flow direction and the predominant orientation of seafloor ridges. Approximately 1100m north (downstream/oceanward) of the grounding line position, a 2-3m tall sinuous sediment wedge is observed crosscutting the along-flow ridges. This feature is unique in this area, lying 200m north of the estimated 2016 GL position, and 200m south (upstream) of the estimated position of the 2011 GL. No other evidence for pinning events is found in the area, arguing smooth retreat since at least 2016. We discuss these observations in the context of the Thwaites system, as well as implications for other ice shelves.
- Publication:
-
AGU Fall Meeting Abstracts
- Pub Date:
- December 2022
- Bibcode:
- 2022AGUFM.C42B..02S