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UBC Theses and Dissertations

Winter dynamics in an epishelf lake Bonneau, Jérémie


The last intact ice shelf in the Canadian Arctic is located at the mouth of Milne Fiord (82.6N, 81.0W), on Ellesmere Island, Nunavut. During melt season, the ice shelf acts as a dam preventing meltwater from flowing freely to the ocean. This results in a permanent layer of freshwater that "floats" on top of the seawater of the fjord. This layer of freshwater is called an epishelf lake. The winter data from a mooring installed in Milne Fiord epishelf lake (2011-2019) is analysed in the framework of a one dimensional model in order to study 1) mixing in the upper water column and 2) the evolution of a basal channel in the ice shelf. The results show that vertical mixing is surprisingly higher in the epishelf lake than in the seawater underneath. Estimation of the Richardson number using geostrophic balance indicates that enhanced mixing in the epishelf lake is associated with horizontal temperature gradients. Moreover, the analysis suggests that all of the freshwater reaching the ocean travels through a single basal channel in the ice shelf. The model did not detect significant variation in outflow characteristics over the eights years of study, implying that the basal channel area is in ice mass balance.

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