Melting and freezing beneath Larsen C Ice Shelf, Antarctica.

• Main Author: Harrison, Lianne
• Format: Thesis
• Language: English
• Published: 2021
• Subjects: Antarc*; Antarctica; Ice Shelf
• Online Access: https://ueaeprints.uea.ac.uk/id/eprint/81443/; https://ueaeprints.uea.ac.uk/id/eprint/81443/1/2020HarrisonLPhD.pdf

Observations of recent surface lowering of Larsen C Ice Shelf (LCIS), Antarctica, and the calving of a large iceberg in 2017, have prompted concern about the stability of this ice shelf. The influence on grounded ice upstream that would result from ice shelf thinning or collapse could affect global sea level rise on decadal time scales. In this thesis, the extent to which oceanic basal melting has driven ice loss beneath LCIS, resulting in the observed lowering, was investigated by simulating ocean conditions in this region using a high resolution ocean model. The model included a new bathymetry containing a southern seabed trough discovered by seismic observations. Ocean circulation within the cavity was found to be separated into two distinct components, connected by an eastward, cross-cavity flow initially steered by the trough. In a simulation using an older seabed without the trough, this circulation was not seen. The greatest melting in the cavity corresponded to the location of rapid, inflowing water from the continental shelf which followed the trough. Using a different, older bathymetry which shallowed significantly in the northern half of the cavity, intense melting shifted from the south to the northeast. In experiments subjected to a uniform ocean warming, an increase in local melting occurred, concentrated in the trough. This does not correspond to the observed northward-intensified lowering of LCIS, suggesting oceanic forcing is not responsible for these changes. The extent of marine ice, deposited when ocean water freezes to the base of the ice shelf and advects downstream, is significantly reduced in critical regions of the ice shelf base when ocean temperatures are raised. As marine ice is thought to stabilise LCIS, potential future ocean warming may therefore lead to collapse. This demonstrates a high sensitivity of LCIS stability to even small changes in ocean forcing.