Vulnerability of Denman Glacier to Ocean Heat Flux Revealed by Profiling Float Observations

Abstract

Denman Glacier, which drains a marine-based sector of the East Antarctic Ice Sheet with an ice volume equivalent to 1.5 m of global sea level rise, has accelerated and undergone grounding line retreat in recent decades. A deep trough and retrograde bed slope inward of the grounding line leave this glacier prone to marine ice sheet instability. The ocean heat flux to the ice shelf cavity is a critical factor determining the susceptibility of the glacier to unstable retreat. Profiling float observations show modified Circumpolar Deep Water as warm as −0.16°C reaches a deep trough extending beneath the Denman Ice Tongue. The ocean heat transport (0.77 ± 0.35 TW) is sufficient to drive high rates of basal melt (70.8 ± 31.5 Gt y−1), consistent with rates inferred from glaciological observations. These results suggest the Denman Glacier is potentially at risk of unstable retreat triggered by transport of warm water to the ice shelf cavity.