Small ice-free oasis helped Arctic marine life survive last ice age

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.

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.

Arctic sea ice shrunk to sixth lowest summertime minimum extent
Washington (UPI) Sep 27, 2018 - Satellite observations suggest the Arctic's sea ice reached its summertime minimum extent on Sept. 19, and then again four days later on Sept. 23.

On those dates, the sea ice surface area totaled 1.77 million square miles -- the sixth lowest summertime minimum extent in modern history, tied with 2008 and 2010.

"This year's minimum is relatively high compared to the record low extent we saw in 2012, but it is still low compared to what it used to be in the 1970s, 1980s and even the 1990s," Claire Parkinson, a climate change senior scientist at NASA's Goddard Space Flight Center, said in a news release.

Every year, ice in the Arctic Ocean grows through the winter months, reaching a maximum in early spring, and then shrinks through summer months, reaching a minimum in early autumn. Satellites and aerial surveys help scientists keep track of the maximum and minimum extents.

Data collected over the last several decades suggests both the Arctic's minimum and maximum sea ice extents are getting smaller over time. Several studies have shown climate change to be having an outsized impact on Earth's poles.

The Arctic experienced a mix of unusually warm and cool weather this summer, leading to intense melting in some regions and the persistence of ice in others.

Scientists were surprised to observe melting at the center of a region of old, thick ice north of Greenland. Aerial surveys conducted earlier suggest the historically thick region of sea ice was thinning.

When ice melts and refreezes, thinning in the process, it can become more susceptible to warmth and air and currents, enabling the transfer of heat to previously insulated regions of Arctic ice.

Earlier this year, scientists found evidence that thermal energy had penetrated deep into the Arctic interior of a period of several decades.

The same pattern -- melting and thinning magnifying the impacts of warm air and water -- appears to be happening throughout the Arctic, across both short and long timeframes.

"This summer, the combination of thin ice and southerly warm winds helped break up and melt the sea ice in the region, reopening the hole," said Melinda Webster, a sea ice researcher at Goddard. "This opening matters for several reasons; for starters, the newly exposed water absorbs sunlight and warms up the ocean, which affects how quickly sea ice will grow in the following autumn. It also affects the local ecosystem; for example, it impacts seal and polar bear populations that rely on thicker, snow-covered sea ice for denning and hunting."

Earlier this month, NASA launched the agency's newest ICE mission satellite, ICESat-2. Scientists hope the probe's more precise laser-based ice measuring system will help them better understand sea ice loss in Arctic.

"We're losing more and more sea ice every year and we don't know why," Tom Wagner, ICESat-2 program scientist, told UPI.

Related Links
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