Through the winter months and immediately after ice off, the upper section of the lake, the epilimnion, is much cooler than the bottom, the hypolimnion, it also contains the majority of lakes oxygen. Throughout the winter, the vegetation at the bottom of the lake has been decomposing and exhausting heat which warms the hypolimnion. Typically 3-10 days after ice off, the epilimnion (upper column) will reach the same temperature as the hypolimnion (bottom column). Then and only then, with the help of a good wind, will the lake mix and effectively “turnover”.
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