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Sea ice and open water off Svalbard (Matthias Forwick loan)
According to a new study, an oasis in the hostile Arctic Ocean has supported marine life and ocean circulation during the last ice age.
In the study, published in Nature Communications, Norwegian and British scientists have shown that 20,000 years ago, the Arctic winter pack ice covered more than double the current area.
However, there was a small ice-free 'polynya' between the frozen continents and the ocean where microscopic marine life reigned, which could have provided fish and mammals with otherwise unavailable food.
The study was led by the Geological Survey of Norway (NGU), the Center for Arctic Gas Hydrate, the Environment and Climate of the Arctic University of Norway and the Center for Chemical Sciences of the University of Plymouth.
The researchers believe that their results are of international importance, as they show the vulnerability of marine ecosystems in the northern oceans to periods of rapid climate change, but also their adaptability to various extreme weather conditions.
Jochen Knies, researcher at NGU and Arctic University of Norway, is the lead author of the study. He said: "We were looking for evidence of biological life in sediments at the bottom of the ocean. In doing so, we found that between the ice-covered oceans and the ice sheets on the mainland, there must be a small ice-free corridor extending for hundreds of kilometers into the Arctic. These ice-free regions are often referred to as "polynyas", a Russian term for an area of open water surrounded by sea ice and / or ice caps.
The research initially consisted of recovering a core of sediments at the bottom of the ocean southwest of the Barents Sea, a region of northern Norway of major importance for the United States. fishing industry today.
Back in their respective laboratories, Norwegian scientists set out to date the nucleus and analyze the fossilized remains of preserved biological organisms, while the Plymouth group analyzed the chemical "fingerprints" of algae living in the area.
The results revealed that the polynya was maintained for at least 5,000 years, when the environment was largely ice-covered and the global ocean circulation was minimal.
During a subsequent period of abrupt climate change about 17,500 years ago, the cold fresh waters of melting ice caps covered the entire northern oceans with thick sea ice and the polynya disappeared. This resulted in a dramatic decline in marine life and took 2,000 years to recover.
Today, such polynyas are common in Antarctica and Greenland and are formed through a combination of offshore winds blowing nearby ice caps and warm water from the depths of the ocean. .
In areas of extreme cold and limited access to food, polynyas are an oasis for the survival of marine mammals and are also essential to the global circulation of the oceans.
Simon Belt, professor of chemistry at Plymouth, said: "Polynyas in the polar regions are common today, but until now it has been very difficult to confirm their existence in the past. However, by finding chemical fossils of algae living on the high seas and in sea ice, we have shown that polynyas must have existed during the last ice age, giving us an idea of the survival of marine life conditions. "
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