Joshua Williams

Active research projects:

PhD Title: Controls on Ice Discharge from the Greenland Ice Sheet

Over the past two decades, the Greenland Ice Sheet has experienced significant mass loss, increases in both the volume and area of surface melt, glacier acceleration and marginal thinning. However, these changes are not uniform – whilst some glaciers, for example Jakobshavn Isbrae, have continued to accelerate, others have slowed or stabilised. Moreover, there are clear differences between the processes controlling land-terminating and marine-terminating glaciers. Consequently, key processes controlling the dynamic behaviour of Greenland’s outlet glaciers are poorly constrained, and are thus not represented in the ice sheet models that form the basis of the IPCC sea level rise projections. An improved understanding of the factors driving current variability is required.

My project aims to extend the historical ice velocity record for the Greenland Ice Sheet. This is achieved through the automatic tracking of the displacement of surface features, such as crevasses, between pairs of satellite images. Not only does the project aim to extend the temporal coverage of ice velocity measurements, but an
improvement to the feature tracking code will improve the spatial coverage, allowing the delineation of velocities further inland.

This furthering of the ice velocity record will extend confidence on velocity trends and improve the potential for determining the significance of the atmosphere and/or the ocean in forcing a dynamic response in Greenland’s marine-terminating glaciers. In turn, this will feed in to the improvement of ice sheet models and thus sea level rise projections, offering the potential for clear communication to publics, given that sea level rise provides an unambiguous quantification of the impacts of climate change upon the ice sheets.