One of the comments said just that. "Grounded near disko bay" iirc.

Another comment said that icebergs melt blow water faster than in the air and that flipping is a fairly common thing to do because the center of gravity changes.

You can see bathtub rings on the underside as it's lifted up. The rings are caused by it's melting faster under the water than in the air, so there's a discontinuity at the waterline.