What is lake turnover?

In the summer, the lake “stratifies” or develops layers of different temperatures that do not mix. Perhaps you’ve noticed the effect– have you ever kicked into a cooler layer while swimming at the warm surface? As fall nights chill the lake’s surface, the top layer of water cools, becomes heavier, and eventually sinks. Water that was at the bottom of the lake is displaced– it rises to the top, bringing with it lots of bottom nutrients. Fall winds mix these layers, distributing oxygen and nutrients from top to bottom, until ice forms.