A very interesting new climate theory the one mentioned today at Science Daily: while the cooling of Earth was caused by orbit perturbations, leading to the closure of Bering Strait and the formation of the Beringia isthmus, this last caused such perturbation in global oceanic currents that in the long run sentenced the Ice Age to its end.
The Atlantic Ocean is saltier than the Pacific, what leads to water flowing from this latter to the former. This circulation can only go through the south or via the Arctic Ocean. With Bering Strait closed, Atlantic salinity grew and the North Atlantic Conveyor (Gulf Stream) was enhanced leading to a gradual meltdown of the North Atlantic Ice sheets (in North America and Northern Europe), which in turn lead to higher sea levels and eventually to the reopening of the Bering Strait and the stabilization of climate in the Holocene.
It took many many thousand years though.