Circulation and ocean-ice shelf interaction beneath the Denman and Shackleton Ice Shelves

Area of Science:

• Oceanography
• Glaciology
• Climate Science

Background:

• Ocean-driven basal melt is a critical factor in ice shelf thinning and weakening.
• Ice shelf buttressing is vital for regulating ice flow into the ocean and impacts sea level rise.
• Observing melt processes within ice shelf cavities presents significant challenges.

Purpose of the Study:

• To investigate the oceanographic processes driving basal melt in the Shackleton Ice Shelf cavity.
• To quantify the impact of different water masses on ice melt rates.
• To assess the stability of the Denman Glacier grounding line in response to ocean forcing.

Main Methods:

• Deployment of floats to gather oceanographic data within the ice shelf cavity.
• Analysis of water temperature, salinity, and current data at various depths.
• Inference of ocean circulation patterns and melt rates based on observational data.

Main Results:

• Warm water intrusion at depth beneath Denman Glacier drives substantial basal melt.
• Widespread but weak basal melt occurs beneath the remainder of Shackleton Ice Shelf due to colder surface-associated waters.
• Four stacked overturning circulation cells were inferred in the Denman Glacier cavity, each associated with distinct basal melt driven by specific water masses.
• The Denman Glacier cavity is sensitive to changes in warm water layer thickness, indicating potential for accelerated melt and unstable retreat.

Conclusions:

• The basal melt regime of Shackleton Ice Shelf is heterogeneous, with Denman Glacier being particularly vulnerable to ocean warming.
• Current ocean conditions suggest Denman Glacier is delicately balanced, with potential for rapid retreat if warm water incursions increase.
• The rest of the Shackleton Ice Shelf is currently less exposed to warm water, but this could change with altered ocean circulation patterns.