Arctic Ocean was once a tub of fresh water covered with a half-mile of ice – Livescience.com

The Arctic Ocean was once a pool of fresh water capped with an ice shelf half as thick as the Grand Canyon is deep. 
If that’s hard to envision, don’t despair. Scientists were surprised at the discovery, published Wednesday (Feb. 3) in the journal Nature
, as well. The trick to envisioning this odd arrangement is to think about the relationship between ice sheets and the ocean. When ice sheets melt, they dump water into the ocean, raising the sea level. But when ice sheets grow, as they have during…

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