The stability of the Greenland ice sheet in a changing climate
BSc Physical Geography – 1st class
MSc(Res) Polar and Alpine Change – awaiting grade
Active research projects:
The role of ice melange in ice sheet – ocean interaction
Background: Mass loss from the Greenland Ice Sheet has increased rapidly in recent years, in part due to the dramatic retreat, thinning and acceleration of marine-terminating outlet glaciers. A leading hypothesis is that this behaviour has been caused by increased submarine melting at the calving fronts of these glaciers, driven by ocean warming. In turn, increased discharge of meltwater and icebergs affects ocean circulation, ecosystems and shipping hazards. It is thus crucial that we understand processes occurring at the interface between the ice sheet and the ocean. An overlooked feature of this environment is the ice mélange, a matrix of icebergs and sea ice that can choke the inner reaches of fjords (Figure 1). Having calved from the ice sheet, icebergs melt as they pass slowly through this mélange, inputting vast quantities of freshwater into the fjord. Estimates of submarine melt rates at Greenland’s glaciers may therefore be exaggerated, with much of the meltwater present in fjords instead originating from iceberg melt. Furthermore, this melting means that estimates of iceberg and meltwater output from marine-terminating glaciers may be a poor representation of the true quantities leaving fjords and entering the ocean. In this way, the effects of the ocean on the ice sheet and the ice sheet on the ocean may both be misrepresented at present.
Project outline: This project will explore these issues in three parts. Firstly, modifications will be made to the MIT General Circulation Model (MITgcm) to allow the submarine melting of ice mélange to be modelled. The modelled rate and distribution of mélange melting will then be compared to that inferred from remote sensing of mélange at Kangiata Nunata Sermia (Figure 1), improving understanding of controls on and thus prediction of melt rates in a wider range of fjords and under various warming scenarios. Finally, model results will be used to assess the effect of ice mélange melting on existing estimates of submarine melt rate at Greenland’s outlet glaciers. Combined, these objectives will provide a greatly improved understanding of the controls on and rates of submarine melting (both of the mélange and glacier calving fronts) and the role of fjord processes in modifying the proportion of icebergs and meltwater exported to the shelf.