An oasis in the Arctic maintained marine life during the ice age
In a study, researchers from Norway and the UK show that the Arctic sea ice 20,000 years ago covered an area twice the size that it currently does. Yet there was a narrow ice-free oasis with marine life between the ice-covered continents and the sea.
Researcher Jochen Knies at the Geological Survey of Norway (NGU) and Center for Arctic Gas Hydrate, Environment and Climate (CAGE) at UiT – Norway’s Arctic University, led the Norwegian side of the study:
– When we looked for evidence of biological life in sediments on the seabed of the Arctic, we found that between ice-covered seas and icecaps there must have existed an ice-free corridor that stretched for hundreds of kilometres. Such ice-free areas are called «polynyas» – a Russian term of an area of open water surrounded by ice, Knies explains.
Sea winds and warm water
Currently, polynyas are usually found around Antarctica and Greenland. They are established through a combination of ocean wind blowing from nearby ice-caps and warm water from the deep. In areas of extreme cold and little access to food, polynyas are oases where marine mammals can survive, and also crucial for global ocean circulation.
Simon Belt, professor of chemistry at Plymouth University, who led the study from the UK, states that polynya in the polar regions is common today but that it is difficult to confirm that they have existed in earlier times.
– But by finding chemical fossils of algae living in the open sea and in sea ice, we have proven that polynya must have existed during the last ice age, he says.
The findings, which are published in Nature Communications today, also show that polynya existed for at least 5,000 years, as the area was still largely covered with ice, and the global ocean circulation was minimal. In a later period of rapid climate change around 17,500 years ago, cold fresh water provided by the melting icecaps, led to that all the northern seas were covered with thick sea ice – and the polynyas disappeared.
This resulted in a dramatic decline in marine life, which it took up to 2,000 years to recover from.
The research is of international importance since it shows the vulnerability of marine ecosystems in the northern seas during periods of rapid climate change, but at the same time shows the adaptability of life to various extreme climate conditions.
Nordic Seas polynyas and their role in preconditioning marine productivity during the Last Glacial Maximum by Jochen Knies, Denizcan Köseoğlu, Leif Rise, Nicole Baeten, Valerié K. Bellec, Reidulv Bøe, Martin Klug, Giuliana Panierie, Patrycja E. Jernas, Simon T. Belt, Nature Communications, doi: 10.1038/s41467-018-06252-8.
© NGU / #Norway Today