Winter Dynamics In An Epishelf Lake: Quantitative Mixing Estimates And Ice Shelf Basal Channel Considerations

Milne Ice Shelf is located at the mouth of Milne Fiord (82.6 degrees N, 81.0 degrees W), on Ellesmere Island, Nunavut. This floating ice feature is attached to both sides of the fjord. During the melt season, the ice shelf acts as a floating barrier preventing surface runoff in Milne Fiord from flowing freely to the ocean. This results in a permanent layer of freshwater that floats on top of the seawater of the fjord, commonly known as an epishelf lake. Few studies address the physical characteristics of epishelf lakes. Here, winter data from a mooring installed in Milne Fiord epishelf lake during 2011-2019 is analyzed in the framework of a one-dimensional model in order to study mixing in the upper water column and infer the characteristics of a basal channel in the ice shelf. The results show that vertical mixing rates are higher in the epishelf lake than in the seawater below. Estimation of the Richardson number using a geostrophic balance approach reveals that enhanced mixing in the epishelf lake is associated with horizontal temperature gradients. In contrast to most studies on basal channels in Greenland and Antarctica, the results presented here show the basal channel of Milne Ice Shelf is apparently not evolving (melting) rapidly.