Suppose I have a container of water with a ball floating on top of it. I put it outside overnight and the water freezes. Since the water’s volume increases as it freezes, the ball is raised. Where does the increased gravitational potential energy come from?

I noticed this morning that I had left a watering can outside and it was full of ice.

I suppose the ball is not completely necessary as I could be asking about the gravitational potential energy of some of the water itself. Since the water expands as it freezes into ice, and its shape is bounded by its container, presumably some of it ends up higher up as ice than it was as liquid.