Something magical happens this time of year for our Great Lakes. It's called 'Turnover', and it's pure physics. It's one of the things that got me into physics as a young nerd, and is much better than philosophy.
Water has some fantastic physical properties, which, if changed just a little, would be the end of life. Philosophy can debate this forever, with a lot of 'what if's', but the hard-core can state that if any properties were different, we wouldn't have phillies to lip-flap.
Water has great properties at the top end to prevent any phillie 'run away'. But we are interested in the low end, during our coming ice age. Heat energy is just the vibration of molecules. In most liquids, this vibration ensures maximum packing, and the vibration expands the distance between molecules as the temperature goes up.
So, for every other liquid, the density (packing) increases as the temperature goes down. But at 4C, water has the electrostatic forces take over. They start to produce crystals, but still liquid. The density decreases until freezing. This saves all the fishies in the northern lakes.
In terms of heat energy, the lakes gush it out like giant furnaces until the surface gets to max density. Then the top water sinks to the bottom until the whole lake is at 4C. The fishies would be dead without this, because turnover oxygenates the whole lake. That's about 90% of the heat energy flowing out.
The heat shields fail, because now we just have a surface effect. The water freezes to ice and the ice floats. No more deep energy.
We are now at that stage. You look at the temp maps and all the Great Lakes are at 4C or below. Turnover is complete, the warp engines are dead. Toronto will hit -30. Huntsville will hit -40 once the lake freezes over. We are back into the 70's.
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