Modelling landfast sea ice and its influence on ocean–ice interactions in the area of the Totten Glacier, East Antarctica

Abstract

The Totten Glacier in East Antarctica is of major climate interest because of the large fluctuation of its grounding line and of its potential vulnerability to climate change. The ocean above the continental shelf in front of the Totten ice shelf exhibits large extents of landfast sea ice with low interannual variability. Landfast sea ice is either crudely or not at all represented in current climate models. These models are potentially omitting or misrepresenting important effects related to this type of sea ice, such as its influence on coastal polynya locations. Yet, the impact of the landfast sea ice on the ocean–ice shelf interactions is poorly understood. Using a series of high-resolution, regional NEMO-LIM-based experiments, including an explicit treatment of ocean–ice shelf interactions, over the years 2001–2010, we simulate a realistic landfast sea ice extent in the area of Totten Glacier through a combination of a sea ice tensile strength parameterisation and a grounded iceberg representation. We show that the presence of landfast sea ice impacts seriously both the location of coastal polynyas and the ocean mixed layer depth along the coast, in addition to favouring the intrusion of mixed Circumpolar Deep Water into the ice shelf cavities. Depending on the local bathymetry and the landfast sea ice distribution, landfast sea ice affects ice shelf cavities differently. The Totten ice shelf melt rate is increased by 16% on average and its variance decreased by 38%, while the Moscow University ice shelf melt rate is increased by +54% in winter. This highlights the importance of including an accurate landfast sea ice representation in regional and eventually global climate models.