I think what you are talking about is an asteroid impact on Earth that melted Greenland's ice sheet?

If you look on Google map ...east coast United States ..then go north up to Nova Scotia you can see just north of Nova Scotia almost at the shoreline there is a huge old impact crater..looks to be mostly filled in now...but it made a large circular bay there..probably millions of years ago..

Could have been the reason we had a crustal shift of the Earth 2 million years ago..a shift which, at that time, took almost 1 million years to complete..which means nobody alive at the time would have noticed it..it was moving so slow..but eventually they would have noticed the weather patterns changing and temperatures not what they should be.

Could be whats in store for us if this continues ..due to the loss of the northern hemispheres ice..and the gradual build up of the southern hemispheres ice in Antarctica. Too much weight in the southern half of our planet could eventually cause it to straighten up ..since our world is canted at an angle while it spins..it theoretically could straighten the heaviest portion being at the very bottom of our planet..causing a crustal shift. However long it takes would determine if we could survive it or not...like in the last one, which took almost a million years to finish..but if it happened allot faster..there would be almost complete devastation of all coastal cities on Earth, crop failures, massive earthquakes and tsunami's, volcanic activity beyond belief and a certainly large reduction in humanity's population globally.