In November, I wrote of the pools of water that have collected on top of the biomeiler. They continued to freeze over and melt open as the weather conditions fluctuated. Their presence hinges on how the weather alters the rate at which heat arrives from below and the rate at which it is removed from above.
The main picture shows how the pools were still present in December until the cold spell began. Now, in January, the outdoor temperatures have warmed significantly, but the pools have not, yet, uncovered themselves. The readings from the thermocouples in the pile indicate that the composting in the upper part of the pile is losing its vigor. In consequence, the rate of heat production may no longer be sufficient to allow for open water on the surface of the pile. However, evidence exists to prove that the snow cover continues to melt.
In the above left picture, you can observe large depressions in the snow cap. These depressions are a clear indicator of unequal heating from below. In a few places, water has leaked over the edge of the pile and formed large icicles. Snow has a considerable talent for forming bridges over warm areas beneath it and I am sure that is the case here. I am confident that, if I were to scrape the snow cover away from the areas with thinner cover, I would uncover pools of water hidden just below.
Conduction, convection, radiation, the addition of freshly fallen snow, and the evaporation of the warm water all combine to push and pull the pools back and forth across the melting point. When I go out to do the chores I often stop to examine the pools or the pattern of depressions in the snow cap and speculate as to which of these processes currently dominates the situation.
“There is more beauty in the eye of the beholder who knows what to look for.” That quote is from Paul Hewitt, who wrote a physics textbook I sometimes referred to in my classes. I made a poster of this quote and had it on the wall of my classroom for many years.
One of my goals as a teacher was to show students how learning about science would allow them to see what wonders hide in plain sight all around them. It is probably a large part of why I now write these blog entries.
I wonder whether the frozen pooling will cause early air conditioning that was so helpful last summer!
Because it is external to the pile, I suspect it won’t help with cooling.
Any surface ice would likely melt with the rest of the outdoor snow in the spring.