That's so interesting. Looking at the rocks and then the paths behind them, it's very difficult to conceive that a much larger body is at work in the process. Once you see the size of those ice sheets, it becomes clear that enough force is there.
I've pushed broken ice sheets around in a pond, and they don't need to be very big to be very heavy. I expect that if the water level rises during the thawing (if wind blows more water into that area), then the rocks stuck in the ice might even be lifted as well as dragged.