Inverting surface-elevation data for basal topography beneath Thwaites Glacier, West Antarctica

Abstract:

Thwaites Glacier in the Amundsen Sea sector of West Antarctica has some of the highest observed rates of ice thinning in Antarctica, and satellite records show the ice loss is accelerating. One of the key controls on the future retreat of the glacier is the topography of the bed beneath it, which slopes inland, deepening over a series of cross-flow ridges. Although there is extensive data coverage for the surface of the glacier, the only way to observe the bed directly is through radar and seismic surveys, which are currently spaced too far apart to provide the bed resolution required for models of the glacier’s future behaviour. However, high resolution radar grids from Pine Island show a remarkable resemblance to the surface of the ice above them, suggesting that in fast flowing ice streams the shapes of landforms at the bed may be reflected in the ice surface. Here we present a new high resolution map of the bed topography beneath Thwaites Glacier derived using linear perturbation theory and the high resolution REMA surface DEM. The inverted bed topography has similar statistical properties to recently published offshore bathymetry in Pine Island Bay, and matches well with existing airborne radar lines and swath radar surveys from the region, but has significantly more detail in the areas between current radar lines. These new topographic features are of potential importance for the future behaviour of Thwaites Glacier, as modelled patterns of ice retreat are strongly influenced by form drag over the topography. The method has potential for improving the resolution of bed topography in other fast flowing regions of Antarctica.