Bottom-fast ice pan domed by spring meltwater influx during breakup
This is a photo of a small tundra lake early in the breakup season. Note that the central area of the ice pan, which is bottom-fast around its edges, is raised with respect to the areas nearer the shoreline. This lake is in the southwestern part of Nunavut, Canada, and was photographed from ca. 600 m altitude in the spring of 1975. Lakes in this region freeze over during low water level conditions in the fall. The ice pan reaches thicknesses of about 2 m in this area and is frozen to the bottom of the lakes to this depth. The pan is only released to float when the force of its buoyancy exceeds the strength of the freezing bond, at which point all parts of the pan rise abruptly to form a flat ice surface. In this example, which is typical of this early stage of breakup, ice is frozen to the bottom around the lake’s edges, and the spring melt water is flowing into the lake beneath the ice cover causing the ice in the central part of the pack to be domed. Water typically pools in the depressed “race track” along the shore until the buoyancy of the ice breaks the frozen bond to the bottom. For further discussion see image 0047 as well as images 0123, 0124, 0126, 0203, 0204 and 0206.
Updated 04/07/2010 AW