03-16-2007, 02:55 AM
Jacksonlaker,
Yes, I researched the turnover deal myself and you are correct about water being most dense at 39 F.
I am no expert, but based on what I read, the stable configuration both summer and winter will put the 39 F water on the bottom since it is most dense. The difference is that in winter, 39 F water is warmer than the remainder of the water profile (or certainly warmer than the ice at the surface and the water near the ice). The opposite would be true in summer where you have the coldest water on the bottom - that could be 39 F on the bottom or warmer since water becomes less dense with increasing temperature starting with 39F. It would typically become incrementally warmer as you head toward the surface during the summer.
The one report that I read said that after ice-out, there is a period where the surface water warms to 39 F and the middle is cooler and the bottom is 39 F, so density-wise you temporarily have a sandwich with lighter water caught in between. It takes wind or some other disturbance to make the top water shoot to the bottom where it mixes and displaces enough of the low-oxygen bottom-water to junk up the lake.
It makes my head hurt to think too much about this because it is pretty confusing. It is not clear why the 39F water on the surface does not slip down, one molecule at a time (water is a fluid after all), but there are enough people swearing to the phenomenon that I assume they have a solid basis for saying so. It sounds like water is pretty unique in that most other substances have their peak density on the bottom end of the temperature scale rather than in the middle. I guess we are lucky that water is the way that it is or there would be no ice fishing.
FR
[signature]
Yes, I researched the turnover deal myself and you are correct about water being most dense at 39 F.
I am no expert, but based on what I read, the stable configuration both summer and winter will put the 39 F water on the bottom since it is most dense. The difference is that in winter, 39 F water is warmer than the remainder of the water profile (or certainly warmer than the ice at the surface and the water near the ice). The opposite would be true in summer where you have the coldest water on the bottom - that could be 39 F on the bottom or warmer since water becomes less dense with increasing temperature starting with 39F. It would typically become incrementally warmer as you head toward the surface during the summer.
The one report that I read said that after ice-out, there is a period where the surface water warms to 39 F and the middle is cooler and the bottom is 39 F, so density-wise you temporarily have a sandwich with lighter water caught in between. It takes wind or some other disturbance to make the top water shoot to the bottom where it mixes and displaces enough of the low-oxygen bottom-water to junk up the lake.
It makes my head hurt to think too much about this because it is pretty confusing. It is not clear why the 39F water on the surface does not slip down, one molecule at a time (water is a fluid after all), but there are enough people swearing to the phenomenon that I assume they have a solid basis for saying so. It sounds like water is pretty unique in that most other substances have their peak density on the bottom end of the temperature scale rather than in the middle. I guess we are lucky that water is the way that it is or there would be no ice fishing.
FR
[signature]