At the end of the last ice age, the ice in North America melted. Then all was the meltwater a huge pool of fresh water. There are the North American lakes remains of. After this there was an ice dam on the east coast which broke later. All that water flowing formed the St. Lawrence River. The diluted salt water, cold water with the result that it is no longer dropped to the bottom, and therefore delayed which "pump" and hence also the heat distribution. Then again, there was an ice age in Europe from 900 to 1000 years. The transition from the climate we have now to an ice age took place in less than 10 years. With a jump so but that will not last again for North America is not covered with ice. Is there perhaps a large chunk of ice in your neighborhood? Oh well here we come back to.