Modelling subglacial discharge and its influence on ocean heat transport in Arctic fjords
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Tidewater outlet glaciers are directly connected to the ocean via ice walls or floating shelves. Melting and freezing of ice, runoff, englacial, and subglacial discharge of freshwater and ocean heat transport are therefore potential feedback processes between glacial ice flow and ocean circulation. Subglacial discharge occurs at the base of tidewater glacier outlets where out-flowing freshwater forms a convective buoyant plume ascending close to the glacier face and, due to entrainment, transports relatively warm and saline ambient bottom water up towards the surface. Plume dynamics, typically occurring at sub-grid scales in regional ocean models, therefore has to be parameterized in areas where ice-ocean interactions occur, as for example in Arctic fjords. Here, we develop and analyze a new simple boundary condition of subglacial discharge where entrainment-induced transport between the subsurface and surface layer is described. A sensitivity study showed that subglacial discharge increased ocean heat transport near the glacier whereas the impact from plume-entrainment became relatively small further from the glacier. Subglacial discharge was shown to have a significant influence on surface concentrations. The impact from subglacial discharge was demonstrated in a regional model of Godthåbsfjord (64°N), located at the west coast of Greenland, where surface concentrations near the glacier were shown to be sensitive to subglacial discharge in accordance with observations.
KeywordsFjord circulation Subglacial freshwater discharge Heat transport Tidewater outlet glacier Ocean glacier interaction Buoyant plume convection
This study received financial support from IIKNN Greenland, the Danish Agency for Science, Technology and Innovation, the Danish Energy Agency, and Aage V. Jensen Charity Foundation and is a part of Greenland Climate Research Centre activities and the Greenland Ecosystem Monitoring Program (www.g-e-m.dk). Funding was also provided by the Nordic Centre of Excellence program (DEFROST), the National Science Foundation (UAF 10-0033A), the Canada Excellence Research Chair (CERC) Program. This is a contribution to the ArcticNet Networks of Centres of Excellence and the Arctic Science Partnership (asp-net.org).
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