I believe this is caused from the weight of the snow causing ice to sink.
As long as you have sufficient ice, don't worry about it too much
. Here in the u.p where we get some heavy snows this happens quite often.
Want to really get worried?
3 Years ago we were on lake Antoine at the festival and a dumb@!! pulled his pick-up about 5 feet from our shack and my pickup was on the other side.
The water came up in shack FAST.
Sunk probably 6 inches right away.
Did not know I could still move that fast.
Ice was only about 10 inches thick, When water started out the door the guy put his truck in gear and took off.
After a few beers and a couple words we laughed about it.
No harm done. Had to move shack though, it would have froze in solid. Have fun and good luck