"Evidence of glacial Lake Agassiz occurs over an area of roughly 365,000 square miles, an area five times the size of the state of North Dakota..."
Thanks - I spelled the name wrong in my search and was having a heck of a time!
One site had Lake Agassiz with a volume of about 157,000 cubic kilometers of water. (I think it was Agassiz, but there were several different ice age dam bursts at different times).
The largest glacier in Iceland is 8,167 sq. km in size, and maximum thickness of 1,000 meters. So only 8,167 km-cubed of ice. (And even less volume once it is melted).
But, this could be the start of a very bad cold spell. And if you are of the belief of a cyclical nature to the earth, we are past due for a true ice age anyway.