Thermocline scientist question

[DangrsDaveO]

During the summer with a little tweaking I can spot the thermocline on my Lowrance. I use a Vexilar for ice fishing and have for several years. So I have a couple of questions:

1. Has anyone used electronics during winter that shows a thermocline and if so which electronic device is it?

2. Is there a thermocline on river feed lakes? If so genereally speaking is it lower or higher during winter months?

I am sure someone out there is a thermocline scientist or expert. Thanks for your reply in advance.

[Castinski]

The water temp gradient is not set up that way in the winter. In fact, the coldest water is just beneath the ice. The thermocline can be found by taking temps throughout the water column. The depth with the steepest temp drop will be the thermocline.

[Zoobert]

From what I understand, on our lakes in the winter months, when the lakes freeze over finally - the thermocline is pretty much at the bottom of the lake, and doesn't change until spring thaw.

Quote:

As the temperature continues to drop, the water on the surface may get cold enough to freeze and the lake/ocean begins to ice over. A new thermocline develops where the densest water (4 °C) sinks to the bottom, and the less dense water (water that is approaching the freezing point) rises to the top. Once this new stratification establishes itself, it lasts until the water warms enough for the 'spring turnover,' which occurs after the ice melts and the surface water temperature rises to 4 °C. During this transition, a thermal bar may develop.

[frazwood]

I'm not an expert on thermoclines, but I think that I can answer your question.

Thermoclines exist because the density of water is highest at about 39 degrees (go here for a table of water density vs. temp: http://en.wikipedia.org/wiki/Properties_of_water). That is, in the summer... the lighter/warmer floats to the top and the heavier/denser water sinks to the bottom. Because most lakes are not mixed well, eventually a thermocline forms where this temperature change is very abrupt.

So, to answer your question, there will never be a thermocline when you are ice fishing because the warmest/heaviest water will be at the bottom (about 39 degrees) and the coldest/lightest "water" (we called it "ice") will be on top.

In a few lakes, especially in the Metro region, you might see something similar to a thermocline in the winter. It's called a chemocline, in which saltier/heavier water sits on the bottom of the lake. These are called meromictic lakes and the lower/salty layer is pretty much permanent. I think that Lake McCarrons in Roseville is an example of a meromictic lake.

As far as rivers, I would imagine that a thermocline could form assuming that the current is not strong and the river is fairly deep.

[mallardnwalleye]

The thermocline and disolved oxygen levels aren't really that defined in the winter. The water on the bottom has the least DO and the water closest to the surface has the most DO. this is why on winter kill lakes all the fish will be up close to the ice. In most clear open lakes Dissolved oxygen isn't a problem in the winter. On a winter kill lake when the winter is long and snowy cut a spear hole in the ice and you can litterally have fish covering the hole.

It would amaze you if you knew how shallow the thermocline is in the summer. On many lakes it's 15-25 ft. not 30-40 ft like I once thought.