Why is my pond / lake melting when the temperature is still far below freezing? I recently moved into a new house with a 2 acre lake behind it. We’ve had 15 consecutive days below freezing, and the last 12 of those have been below 20 degrees (Fahrenheit)! Six days ago I shoveled off a small spot to test out whether it would be good to ice skate on the surface, with the plan that yesterday I would shovel off a much bigger area. Yesterday morning, however, I woke up to a big area straight across starting to melt! The temperature was about 5 degrees F. This morning it’s even larger. The temperature did not exceed 20 degrees yesterday. Though there has been frigid cold it has been sunny. Is it possible that the area I shoveled caused this? The rest of the lake looks exactly the same (About 2” of snow all over it. No signs of melting anywhere else.) I’ve attached before and after pictures. Can’t figure out how in the world this could happen. Any ideas?
My guess is that since ice (and the liquid water underneath it) is much better at absorbing thermal radiation than air, then even if the air temperature is below zero, the ice can heat up in the sun and melt a little bit. It will presumably then refreeze at night when there is no sun to keep it warm.

This was probably also happening on the surface of the snow as well before you cleared it but you didn't notice it because there was no colour change.