Arctic Ocean was once a tub of fresh water covered with a half-mile of ice
By Stephanie Pappas - Live Science Contributor 9 hours ago
At at least two points in history, the Arctic was cut off from other oceans.
(Image: © Alfred Wegener Institute/Martin Künsting)
The Arctic Ocean was once a pool of fresh water capped with an ice shelf half as thick as the Grand Canyon is deep.
When sea levels were low, the Arctic Ocean was cut off from other oceans while still receiving freshwater input from rivers and glaciers.
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 Earth's glacial periods, sea level drops.
Now, new research shows that in these eras of lower sea level, the Arctic Ocean's connection to the Pacific and Atlantic was very limited, with Greenland, Iceland, and northern Europe and Siberia acting as the rim of a bowl containing the Arctic. (Ice itself could have further restricted circulation.) Land and sea alike were overlain with an ice sheet 2,952 feet (900 meters) thick.
Glaciers, river outlets and runoff from the continents kept fresh water flowing into this cordoned-off Arctic Ocean, while saltwater from the Atlantic and Pacific couldn't get in. The exact timing of the freshening process isn't clear, but the researchers calculated that it could have happened in around 8,000 years.
"These results mean a real change to our understanding of the Arctic Ocean in glacial climates," first study author Walter Geibert, a geochemist at the Alfred Wegener Institute Helmholtz Centre for Polar and Marine Research, said in a statement. To our knowledge, this is the first time that a complete freshening of the Arctic Ocean and the Nordic Seas has been considered happening not just once, but twice."
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