Seasonal variability of submarine melt rate and circulation in an East Greenland fjord. Issue 5 (17th May 2013) - Sciascia, R.
Abstract : [1] The circulation in a glacial fjord driven by a large tidewater glacier is investigated using a nonhydrostatic ocean general circulation model with a melt rate parameterization at the vertical glacier front. The model configuration and water properties are based on data collected in Sermilik Fjord near Helheim Glacier, a major Greenland outlet glacier. The approximately two‐layer stratification of the fjord's ambient waters causes the meltwater plume at the glacier front to drive a "double cell" circulation with two distinct outflows, one at the free surface and one at the layers' interface. In summer, the discharge of surface runoff at the base of the glacier (subglacial discharge) causes the circulation to be much more vigorous and associated with a larger melt rate than in winter. The simulated "double cell" circulation is consistent, in both seasons, with observations from Sermilik Fjord. Seasonal differences are also present in the vertical structure of the melt rate, which is maximum at the base of the glacier in summer and at the layers' interface in winter. Simulated submarine melt rates are strongly sensitive to the amount of subglacial discharge, to changes in water temperature, and to the height of the layers. They are also consistent with those inferred from simplified one‐dimensional models based on the theory of buoyant plumes. Our results also indicate that to correctly represent the dynamics of the meltwater plume, care must be taken in the choice of viscosity and diffusivity values in the model. Key Points: Fjord dynamic and submarine melting are strongly influenced by seasonality Our findings are consistent with observations and with simplified plume models To represent the dynamic care must be taken when choosing model parameters