Numerical modelling of the sub-surface melting of marine-terminating glaciers in Arctic fjords

Submarine melting of glaciers terminating in fjords is likely to be of high importance regarding the total ice loss from ice sheets and ice caps and the resulting addition of freshwater to the ocean. Submarine melting generates a buoyant plume which ascend along the calving front of the glacier and sets up a circulation. In addition, surface melt on the glacier drains to the bedrock and gets discharged at depth into the fjord. Earlier, this has been shown to further enhance the buoyancy-driven circulation near the glacier front. The buoyant plume entrains ambient warm fjord water as it ascends, and the circulation it sets up also drives warm fjord water toward the glacier front at depth in order to conserve volume. These processes replenish the near-glacier area with heat available for melting. The purpose of this study is to investigate the submarine melting of marine-terminating glaciers and the resulting buoyancy-driven circulation in fjords in Greenland. First the non-hydrostatic high- resolution Bergen Ocean Model is used in a series of simulations to reproduce earlier results obtained by the Massachusetts Institute of Technology general circulation model with a meltrate parameterization developed for melting beneath ice shelves in Antarctica. The simulated meltrates found in this study are in the range \SIrange{43}{1043}{\metre\per\year}. The melting at the glacier front is sensitive to oceanic thermal forcing following a linear relation and to discharge of surface runoff following a cubic root relation. Then, it is attempted to apply this modelling approach to glacial fjords in Svalbard. The modelled fjords in these simulations are shallower than the deep fjords of Greenland, and the consequences of smaller fjord depth are studied for various forcings. The meltrate ranges from \SI{9}{\metre\per\year} to \SI{895}{\metre\per\year}, and its value is highly sensitive to subglacial discharge, the stratification of the fjord water and the rate of replenishment of warm ambient fjord water to the glacier front by the return current at depth.Master i Meteorologi og oseanografiMAMN-GEOFGEOF39