RM>> Winter is not quite over it seems. It's dropping to -23c (-9f)
  >> here tonight. Funny things happening on the bay as well. I saw
  >> the water level in hole where I get my water vary in depth by
  >> about 14 inches over the past few days.

This morning when I headed out there, the water had totally covered
the lid of my 'box' by over an inch and frozen solid so I had to
chip all around down the the edges of the lid and then pry it out
of the ice..

MP>Yeah, it tried to rear its ugly head around here for two or three days,
  >but that ended last night.  Temperatures rose steadily overnight, and we
  >are about 20F warmer this morning than we were yesterday afternoon.

We will get a little above freezing tomorrow for the first time in
a few days, but the long range still shows some quite cold nights
coming so it's bouncing around.. not that unusual for late Feb and
early March.

MP>I guess as the ice thaws on other parts of the lake, it starts moving
  >around and causes things like that?

It's all one sheet covering almost 100% of Georgian bay so the ice
itself doesn't move around much until it gets warm enough for it
to start breaking up in early spring.

But the thickness of the ice should only change from the bottom,
melting or freezing the water under the ice. When the ice gets
thick enough to safely walk on I cut about a 36" hole in it and
put my covered box, about 40" square and 22" high, over that hole.
In theory that 22" should always be above the ice since no new
ice is being added from above, but I guess water is being forced
out the sides some and building up so that the entire inside of
the box and all around the outside of it is now solid ice, and
now more is coming out and submerging the whole thing.

I've wintered here 15 years in total over the years and I've
never run into anything like this before.

My first thought was that the wind was putting pressure on
the open water making it push water up through my hole in
the ice, but with Georgian Bay almost totally covered in ice
this year, there's very little open water for wind to hit,
and the worst night for it, last night, was not windy at all.

I'm thinking now it must be pressure on the ice from above due
to the weight of the heavier snow load on the ice this winter..

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 * SLMR Rob  * Hold on to me, someday I may be quite valuable
 * Origin: Capitol City Online (618:250/1)