Sack Lunch Seminar (SLS)

Abstract:
Increasing evidence indicates that changes at the marine margin of Greenland’s tidewater glaciers may have triggered their recent acceleration and retreat and sizably increased Greenland’s contribution to sea-level rise. One of the proposed mechanisms involves changes in submarine melting at the ice-ocean interface. Yet the parameters and processes controlling the submarine melt rate are largely unclear. In particular, the influence of surface meltwater released at depth (subglacial discharge) and ocean properties on the meltwater plume dynamics are poorly understood.

This presentation will discuss the variations in submarine melt rate induced by subglacial discharge and wind-driven circulations at the edge of Helheim Glacier, a large outlet glacier of Greenland Ice Sheet. We use a non-hydrostatic, high-resolution configuration of the MITgcm with an ice–shelf parameterization initialized with data collected from Sermilik Fjord, where Helheim discharges, and forced by an observed subglacial discharge. We show that the meltwater plume and the associated submarine melting varies significantly seasonally largely due to changes in subglacial discharge and is less sensitive to the wind-driven circulation. In summer, the submarine melt rate is one order of magnitude larger than in winter and its maximum occurs near the glacier grounding line, while in winter its maximum occurs near the interface between the two water masses characterizing the fjord stratification. Our results are compared with the theory of buoyant line plumes to validate the ability of the model to represent the dynamics at play at the ice-ocean boundary.