USAP-DC

Ice shelves fringe most of Antarctica’s coastline where the ice sheet detaches from the underlying bed and enters the ocean. These expansive floating bodies of ice provide an important bottleneck on seaward flow of ice from the Antarctic ice sheet and sea level rise through their resistive buttressing forces. The ocean melts ice shelves from below, which removes their mass and influences their buttressing capacity. Local regions of thin ice, referred to as channels and crevasses, form in the base of ice shelves from ocean-driven melting and strain-driven cracking. These features represent potential weak points in the ice that are particularly susceptible to increased melting if ocean temperatures rise, because of their high slope angles. Improving understanding of the processes that determine the rate of melting along ice bases of varying slopes has global societal and environmental implications, as it stands to reduce uncertainties in projected sea level rise. This project will study variable melting along sloping ice using a novel field data set collected in a channel etched into the base of Fimbul Ice Shelf, Antarctica in 2024. Results from this project will provide a baseline for how sloped bases of ice shelves melt, which can be used to improve parameterizations of this process in large-scale models responsible for sea level rise projections. This study focuses on ocean-driven melting along sloping sidewalls of local thin points in ice shelves, such as basal channels or basal crevasses. These features are particularly sensitive to oceanographic forcing, as they exhibit high slopes that can melt rapidly when exposed to warm ocean conditions. If this melting is strong enough, then it can erode features to the point that they become unstable, resulting in full-thickness fractures that promote iceberg calving and ice shelf destabilization. Notably, the upstream effect of ice shelf changes related to oceanographic forcing is a major source of uncertainty in projections of Antarctica’s contribution to future global sea level rise, which could amount to 53 cm by 2100. The primary objective of this project is to make significant improvements to the understanding of how the ocean melts sloped ice shelf basal topography under various forcing. The secondary objective is to understand how ice topography then evolves over time from this ocean forcing. The principal study location is Fimbul Ice Shelf, Antarctica, where in situ data was collected with the Icefin underwater vehicle and other instrumentation in January 2024, as part of an international collaboration with the United Kingdom and Norway. Results from this study will be placed into the larger context of ice shelf melting around Antarctica by comparing with previous data collected with Icefin in various oceanographic settings. The goal of this effort is to better constrain the poorly understood coupled ice-ocean processes that control melting along variable slopes. The Icefin data will be analyzed alongside data from surface-based ice penetrating radar, remote sensing, long-term oceanographic mooring, and output from the Finite-Volume Community Ocean Model. This award reflects NSF''s statutory mission and has been deemed worthy of support through evaluation using the Foundation''s intellectual merit and broader impacts review criteria.

Person	Role
Washam, Peter	Investigator and contact
Schmidt, Britney	Co-Investigator
Zabel, Ingrid H

Antarctic Glaciology

Award # 2434858

USAP-2434858_1

Deployment	Type
Fimbul Ice Shelf	field camp

None in the Database