Kennett, Kennett, West, and others think that a comet impact helped break up the ice sheet then. At the end of your linked news story, the quote: "If the Greenland ice sheet melted suddenly it would be catastrophic," may be irresponsible, or is out of context: The Greenland Ice sheet is not going too melt suddenly; it would take 100s of years, unless it was vaporized by impact, in which case it would be the least of our problems. On the other hand, just melting at a higher rate may increase the fresh water content of the NE Atlantic, decrease the density, stop downwelling, and change the Gulf Stream. But, that would lead to cooling of northern Europe, which would be compensated by the global warming. So, no ice age as long as CO2 levels are high.

But, interesting.
Chris