Described on MPR this morning during the weather report, lake turnover is a remarkably simple, yet beautiful, concept I had never heard of before. Perhaps I'm feeling romantic as the holidays approach, but this scientific aspect of life on Earth made me smile and give thanks.
Lake turnover is as basic as it sounds; in essence, lakes turn into themselves to rotate the oxygenated water. The beauty of design is what excites me. Water, Paul Huttner tells me, is at its heaviest at 39 degrees, causing it to "sink" to the bottom. Water begins to freeze at 32 degress, a mere seven degress fewer than the heavy water. So, the living plants and animals at the bottom of a frozen lake all year have the surface water (full of oxygen and nutrients from the summer months) in which to live all winter. If water was heaviest at 29, it would be too late, for it would already be frozen. Tough luck, fishies. But conveniently enough, water sinks before it freezes.
This is too perfectly syncronized to be a mistake.