With all the attention on Clary Lake ice this spring, it seems fitting to post this article I’ve been working on for awhile, yet another in our Continuing Education Series, based on the premise that informed people make better Lake Stewards! This post is on Ice Berms and Pressure Ridges and the science behind them and will be added under the Programs & Education menu heading.
I received a few inquiries about ice berms and pressure ridges in response to my post about February water levels so I thought I’d provide a little more information about these interesting phenomena and the science behind them. Imagine the forces at work that were responsible for the buckled ice in the photo at left! First we need to learn more about how water changes and what happens to it as its temperature changes.
Water becomes more dense (heavier) as its temperature drops, causing it to sink below warmer water: cold water sinks and warm water rises. We all know this much from going swimming and encountering that cold layer of water 4-5 feet below the surface. As its temperature drops, water continues to become more dense and continues sinking below warmer water until it gets down to about 39° F. 
Then something unexpected happens: as the water cools, the molecular motion continues to slow down and as the water starts to assume the crystalline lattice structure that is ice, the distance between the molecules actually increases. The freezing water, rather than continuing to become denser, actually begins to expand, becoming less dense, causing it to float (it is this expansion as it freezes that ends up breaking water pipes). By the time water reaches its freezing temperature of 32° F (0° C) and changes to ice, it has expanded approximately 9% from its maximum density and a complete inversion from the usual summertime temperature stratification takes place. In the winter when the lake is ice covered, the coldest water is right under the ice and the temperature rises as depth increases so the warmest (and densest) water is at the bottom of the lake. This is completely opposite of what we see in the summer time with the warmest water at the surface and the coldest water at the bottom. Continue reading →
Yesterday afternoon Clary appeared to be fully ice covered and I was about to call it, but the bit of snow we received in the night has revealed some open water in the usual spot off the point at the end of Duncan Road, and a seam in the middle of the lake is evident as well, perhaps opened up due to the high wind this morning. In early winter there is often open water off Duncan Point (aka Young’s Point) due to the speed of the current there. We’ll see if the current ice cover will survive the warm and wet coastal storm due to blow through here this coming Friday into Saturday.
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