September 27th 2018

An oasis in the Arctic sustained marine life during the last Ice Age

SVALBARD: Sea ice and open water off the coast of Svalbard. Photo: Matthias Forwick
In a new study, scientists from Norway and the UK have shown that, 20.000 years ago, winter Arctic sea ice covered more than twice the area that it does today. Yet there was a small ice-free oasis between ice covered continents and the ocean where marine life prevailed.

Press release

Jochen Knies, a research scientist from the Geological Survey of Norway (NGU) and the Centre for Arctic Gas Hydrate, Environment and Climate (CAGE) at UiT - The Arctic University of Norway who led the study from the Norwegian side says:

 “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 that extended over hundreds of kilometres into the Arctic. Such ice-free regions are often called “polynyas” – a Russian expression for an area of open water that is surrounded by sea ice and/or ice sheets”.

Offshore winds and warm water

Today, polynyas are common around Antarctica and Greenland. They form through a combination of offshore winds blowing from nearby ice sheets and warm water rising from the deep ocean. In areas of extreme cold and little access to food, polynyas provide an oasis for marine mammals to survive and they are also critical for global ocean circulation.

Simon Belt, Professor of Chemistry at Plymouth University, who led the study from the UK side, said “Polynyas in the polar regions are common nowadays, but it’s difficult to confirm their existence in the past. 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” 

International importance

The new findings, recently published in Nature Communications, also reveal that the polynya was sustained for at least 5000 years, when the surroundings were largely covered by ice, and global ocean circulation was at a minimum. During a subsequent period of abrupt climate change around 17,500 years ago, cold freshwater from the melting ice caps caused the entire northern oceans to be covered by thick sea ice and the polynya disappeared. This resulted in a dramatic decline in marine life and it took up to 2000 years to recover.

The research is of international importance since it shows the vulnerability of marine ecosystems in the northern oceans to periods of rapid climate change, yet their adaptability to various extreme climate states.

ILLUSTRATION: Arctic oasis in front of the NW Eurasian ice sheet during the last Ice Age, 20.000 years ago (from Knies et al. 2018, Nature Communications/Irene Lundquist).

Reference: 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.