Winter Dynamics in an Epishelf Lake: Quantitative Mixing Estimates and Ice Shelf Basal Channel Considerations
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• Jérémie Bonneau,
• Bernard Laval,
• Derek R Mueller,
• Alexander LeBaron Forrest,
• Andrew MacWhorter Friedrichs,
• Andrew K Hamilton
Jérémie Bonneau
University of British Columbia

Corresponding Author:jeremie.bonneau@alumni.ubc.ca

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Bernard Laval
University of British Columbia
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Derek R Mueller
Carleton University
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Alexander LeBaron Forrest
University of California - Davis
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Andrew MacWhorter Friedrichs
UC Davis
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Andrew K Hamilton
University of Alberta
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Abstract

Milne Ice Shelf is located at the mouth of Milne Fiord (82.6$^\circ$N, 81.0$^\circ$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 dam preventing surface runoff 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. 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 1) study mixing in the upper water column and 2) 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. Moreover, the analysis suggests that the epishelf lake water 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 eight years of study, implying that the area of the basal channel is in ice mass balance.