Articles | Volume 11, issue 5
Research article
12 Sep 2017
Research article |  | 12 Sep 2017

Dynamic response of an Arctic epishelf lake to seasonal and long-term forcing: implications for ice shelf thickness

Andrew K. Hamilton, Bernard E. Laval, Derek R. Mueller, Warwick F. Vincent, and Luke Copland

Abstract. Changes in the depth of the freshwater–seawater interface in epishelf lakes have been used to infer long-term changes in the minimum thickness of ice shelves; however, little is known about the dynamics of epishelf lakes and what other factors may influence their depth. Continuous observations collected between 2011 and 2014 in the Milne Fiord epishelf lake, in the Canadian Arctic, showed that the depth of the halocline varied seasonally by up to 3.3 m, which was comparable to interannual variability. The seasonal depth variation was controlled by the magnitude of surface meltwater inflow and the hydraulics of the inferred outflow pathway, a narrow basal channel in the Milne Ice Shelf. When seasonal variation and an episodic mixing of the halocline were accounted for, long-term records of depth indicated there was no significant change in thickness of ice along the basal channel from 1983 to 2004, followed by a period of steady thinning at 0.50 m a−1 between 2004 and 2011. Rapid thinning at 1.15 m a−1 then occurred from 2011 to 2014, corresponding to a period of warming regional air temperatures. Continued warming is expected to lead to the breakup of the ice shelf and the imminent loss of the last known epishelf lake in the Arctic.

Short summary
Meltwater runoff trapped by an ice shelf can create a freshwater lake floating directly on seawater. We show that the depth of the freshwater–seawater interface varies substantially due to changes in meltwater inflow and drainage under the ice shelf. By accounting for seasonality, the interface depth can be used to monitor long-term changes in the thickness of ice shelves. We show that the Milne Ice Shelf, Ellesmere Island, was stable before 2004, after which time the ice shelf thinned rapidly.