Holes in submerged, bottom-fast ice of a small tundra lake during breakup

Location: Southwestern Nunavut, Canada; NTS 65H Henrik Lakes

This is an aerial view from 1000 m altitude of a small lake in the final stages of breakup, probably near Yandle Lake in Southwestern Nunavut. Winter ice is still anchored to the sides of the lake bottom, causing spring runoff to submerge most of the ice surface. Dark circles in the ice are holes melted through it, and when the buoyant ice pan finally releases from where it is frozen to the lake’s bottom, the surface water will be forced through the holes. Where the lake bottom is soft, the vortices resulting from this process will excavate crater-like holes in the Lake’s bottom. These vortices normally propagate to depths of only 4 m or less, so they are confined to soft-bottom (silty sand or silt) shoal areas of the lakes. The holes have been called “strudel” by Reimnitz, Rodeick, and Wolf (1974), who described them as a strictly marine phenomenon, occurring off deltas in the Beaufort Sea, where surface water flowing over ice at low tide was jetted through holes in sea ice as rising tides lifted it. However, these features also are common in lakes north of the treeline. Tundra lakes commonly freeze over when water levels are depressed in the fall, as is common in this semi-arid region west of Hudson Bay, and are easily flooded by spring meltwaters, as in this image, before breakup of lake ice in the spring. See also images 0071, 0119, 0122, 0123, 0124, 0126, 0203, 0204, 0206. These features are also described in Shilts and Dean, 1975.

Updated 03/30/2010 AW