Polynyas are areas of open water surrounded by ice on all sides. They're created by winds, waves and upwelling of water ocean water. Photo by M. Forwick

Sept. 28 (UPI) -- New analysis suggests a small corridor between Norway and the British Isles remained ice-free during the last ice age, offering an oasis of sorts for marine life.

"When we were looking for evidence of biological life in sediments at the bottom of the ocean, we found that between the sea ice covered oceans, and the ice sheets on land, there must have been a narrow ice-free corridor," Jochen Knies, a research scientist at the Arctic University of Norway and Geological Survey of Norway, said in a news release.


Last week, Arctic sea ice shrank to its lowest point this year, the sixth smallest summertime minimum extent in modern history. But during the last ice age, Arctic sea ice was much more expansive, spreading across almost all of the North Sea.

But sediment cores suggest a long but narrow "polynya" -- a Russian term for an area of open water surrounded by ice on all sides -- persisted throughout the glacial maximum.

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Polynyas are more common today. They're formed by winds and warm currents rising from deep in the ocean. They sustain pockets of marine biodiversity and fuel ocean circulation.

"Polynyas in the polar regions are common nowadays, but it's difficult to confirm their existence in the past," said Simon Belt, professor of chemistry at Plymouth University. "However, by finding chemical fossils of algae that live in the open ocean and in sea ice, we have shown that polynyas must have existed during the last ice age."

Researchers detailed their discovery this week in the journal Nature Communications.

Despite the oasis offered by the ancient polynya, research suggests sudden cooling around 17,500 years ago triggered the proliferation of sea ice, diminishing Arctic biodiversity for at least 2,000 years.