Modelling ocean melt of ice mélange at Greenland's marine-terminating glaciers

Greenland’s marine-terminating glaciers have retreated and accelerated in recent decades, contributing significantly to sea level rise. An increase in ocean temperatures, and in particular the increased submarine melting of calving fronts, is often cited as the dominant driver of this retreat. However, the presence of ice mélange and its associated buttressing force on a glacier terminus also has a substantial impact on glacier advance and retreat. The buttressing force theoretically depends on the mélange thickness, and thickness will be modulated by ocean melt rate, but our understanding of mélange melting remains limited, and it is not yet known how melt rates vary across a range of glacial and environmental conditions.

Here, we perform high-resolution numerical simulations using MITgcm to model the melting of ice mélange. In order to map out the parameter space for mélange melting at Greenland’s marine-terminating glaciers, we vary each of the ocean temperature, ocean stratification, the flux of freshwater emerging from beneath the glacier (subglacial discharge) and the mélange geometry. We study how each factor affects the magnitude and distribution of ocean melt of the ice mélange and seek a parameterisation that would allow us to simply predict mélange melt rate. Furthermore, this work is also a step towards including iceberg melting in larger climate and ice sheet models which is important because of the need to improve the characterisation of freshwater fluxes into fjord systems.