It's interesting, because re-freezing Siberia is exactly what some Russian scientists are attempting. Their logic is that by reintroducing megafauna like elk

It's interesting, because re-freezing Siberia is exactly what some Russian scientists are attempting. Their logic is that by reintroducing megafauna like elk and moose into more parts of Siberia, these animals will graze during winter to survive, thus exposing more of the soil, which lets the frost permeate down to further depths and slows down the recession of permafrost. Their logic is sound and experiments have demonstrated that grazing animals do help to reintroduce permafrost, but I seriously doubt their operation is scalable (they are something like a 3-5 man team)