Assessing Controls on Oceanic Heat Delivery to Greenland’s Marine-Terminating Outlet Glaciers

Abstract:

The recent retreat of many of Greenland’s marine terminating glaciers has been coincident with a period of anomalously warm ocean temperatures. It has been hypothesised that warming ocean waters may affect the stability of glacier termini through an increase in the rate of submarine melting or a decrease in the buttressing influence of sea ice and icebergs, both of which could drive an increase in the rate of mass loss through calving. As Greenland’s outlet glaciers typically terminate at the head of lengthy fjord systems, the availability of oceanic heat at the calving front is however dependent not only on the temperature of the water around the Greenland coast, but also on the advection of this heat towards the glaciers by the circulation of the fjord. Assessment of spatial and temporal variation in this up-fjord heat transport may therefore provide a means of examining the role of the ocean in forcing the dynamic variability of these glaciers.

The rate at which oceanic heat is delivered to a particular glacier is likely to depend on a range of environmental factors. These may be oceanic (e.g. shelf water temperature), atmospheric (e.g. glacial melt water input, the strength of along-fjord and along-shelf winds) or topographic (e.g. fjord depth, length, width or sinuosity). Here we assess the sensitivity of up-fjord heat flux to each of these parameters by undertaking a suite of experiments using an ocean model (MITgcm), applied to an idealised fjord system. Through this, we identify those factors that are of greatest importance in controlling the delivery of oceanic heat to Greenland’s marine-terminating glaciers. Our experiments facilitate assessment of 1) how the influence of the ocean may differ from one marine-terminating glacier to the next and 2) how the oceanic forcing of these glaciers may have changed, and continue to change, over time in response to varying environmental conditions.