What Caused the Ice Sheet Melt?

He walks through the sequence carefully: the Older Dryas, then the warming of the Allerød, then a cold spike within that warming period. That spike, he explains, is attributed to massive meltwater discharge from the eastern sector of the great ice sheets pouring down the Hudson River and into the North Atlantic. The question that remains is what triggered the initial melt. What force was powerful enough to destabilize ice sheets on that scale? The evidence shows the transition happened, but identifying the mechanism requires looking at multiple lines of data, cosmic forcing included, and distinguishing between what the meltwater did and what caused it to begin melting in the first place.