Actually they don't embed themselves in the ice, the ice is free floating with very little friction on top of the water and pushes the rocks using inertia from

Actually they don't embed themselves in the ice, the ice is free floating with very little friction on top of the water and pushes the rocks using inertia from the wind. "Lorenz (one of the co-authors of this piece) has disproven his previous theory--that the rocks were temporarily embedded in a slab of ice which then floated."