The coupled response of Totten Glacier, East Antarctica, to 21st century ocean forcing

Abstract:

The Totten Glacier, a major outlet glacier located in the Aurora Basin of the East Antarctic Ice Sheet, has been suggested to be vulnerable to sub-ice shelf basal melting induced by intrusions of warm, modified circumpolar deep water onto the continental shelf. These warm water intrusions have been observed to accelerate ice shelf thinning and promote grounding line retreat along Totten’s southernmost sector, enhancing grounded ice discharge and subsequent sea level rise. In order to assess the future dynamical response of Totten Glacier to these complex ice-ocean interactions, we couple the Ice Sheet System Model to a regional East Antarctic configuration of the MITgcm and perform fully coupled model projections of this region. In addition to a control run, we perform ocean warming and freshening experiments to simulate how Totten will respond to large-scale changes this watermass might undergo in the 21^st century. The coupled model shows improved agreement with observations of both glacial discharge and changes in grounding line position. Our model also captures the observed seasonal cycle of Totten’s ice shelf velocity without the need to implement sea ice buttressing, suggesting that basal melting is the primary seasonal forcing mechanism. In our future projections, we observe a period of stability before sustained grounding line retreat is initiated along Totten’s eastern flank, the pattern of which is constrained by highs and lows in bed topography. Limited grounding line retreat is projected along Totten’s ice plain in the control experiment: The water column is shallow, simulated melt rates are low, and the slope of the bed is prograde in this sector. As the primary region of grounded ice discharge in East Antarctica, understanding how Totten will dynamically respond to future changes in ocean conditions will have global implications on both sea level rise predictions and preparation.