Geography 2010A/B Study Guide - Quiz Guide: Chemocline, Meromictic Lake, Wind Stress
29 Aug 2018
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The rapid absorption of most solar insolation in the upper 10 m or less of lakes is important for the vertical distribution of temperature. As the melt season progresses, the upper part of the lake warms while the deeper water remains cooler. If ice remains, this will limit warming substantially: the maximum density of freshwater is 4 c, so as the surface waters warm above this level, they become less dense, this results in a thermally stratified water column. The upper water is subject to wind stress and typically is well mixed: the lower water column is isolated by the thermocline, and is subject to reduced or no mixing. In most arctic areas, the density contrast between the upper epilimnion and the lower hypolimnion is not great as warming is limited. Hence, during autumn cooling, the lake can return to isothermal conditions and wind- driven mixing of the entire water column.
