Arctic Ocean remained open to life during ice ages, study suggests

For years, scientists have debated the question of whether a thick giant ice shelf once covered the whole Arctic Ocean at the time of the coldest ice cream. Now a new study published in Scientific advances Dispute this idea while the research team found no evidence of the presence of a massive ice shelf of about 1 km. Instead, the Arctic Ocean seems to have been covered by seasonal sea ice – leaving conditions of free assistance and survival even during the most difficult periods of cold in the last 750,000 years.

The newspaper is entitled “Seasonal sea ice cream characterized The Arctic-Atlantic Ice Gateway in the past 750,000 years.”

This discovery gives crucial information for our understanding of how the Arctic reacted to climate change in the past – and how it could behave in the future.

Tiny traces of life in the old mud

Led by the Synergie subsidy project of the European Research Council in the Blue – I2B, the research team studied the nuclei of sediments collected in the seabed from the Central Nordic Sea and the Yermak plateau, north of Svalbard. These nuclei contain tiny chemical fingerprints of algae who lived in the ocean a long time ago. Some of these algae only grow in free water, while others thrive under seasonal sea ice that forms and melts each year.

“Our sediment nuclei show that marine life was active even during the coldest moments,” said Jochen Knies, the main study of the study, based at the ITU of the Arctic University of Norway and co -directing of the Blue – I2B project.

“This tells us that there must have been a light and free water on the surface. You would not see that if the whole Arctic was locked under a plate of ice cream thick.”

One of the key indicators that the team was looking for was a molecule called IP₂₅which is produced by algae who live in seasonal sea ice. Its regular appearance in sediments shows that sea ice came and came with the seasons, rather than staying solid all year round.

Simulating ancient arctic climates

To test the results based on geological recordings, the research team used the model of the AWI Earth system – a high resolution computer model – to simulate the arctic conditions for two particularly cold periods: the last glacial maximum about 21,000 years ago, and a deeper gel approximately 140,000 years ago when large ice caps were covered a lot from the Arctic.

“The models support what we have found in the sediments,” said Knies. “Even during these extreme glaciations, the hot Atlantic water has always sank into the Arctic bridge. This helped prevent certain parts of the ocean from completely freezing.”

The models have also shown that ice was not static. Instead, he changed with the seasons, creating openings in the ice where light could reach water – and where life could continue to prosper.

This research resumes not only our vision of the past climates of the Arctic, but also has implications for future climatic forecasts. Understanding how the circulation of sea and ocean ice has reacted to past climatic extremes can improve models that project future changes into a warming world.

“These reconstructions help us to understand what is possible – and what is not – when it comes to ice coverage and ocean dynamics,” said Gerrit Lohmann, co -author of this study, based at the Alfred Wegener Institute, Helmholtz Center for Polar and Marine Research (AWI) and co -clong with the Blue – I2B. “This counts when you try to anticipate how ice sheets and sea ice could behave in the future.”

Thinking about the giant theory of the ice shelf

Some scientists have argued that the characteristics on the Arctic seabed suggest that a huge anchored ice shelf once covered the whole ocean. But this new study offers another explanation.

“There may be short ice shelves in certain parts of the Arctic during the particularly serious cold phases,” said Knies. “But we see no sign of a single massive ice shelf that covered everything for thousands of years.”

A possible exception could have occurred about 650,000 years ago, when biological activity in the sediment file fell sharply. But even then, the evidence indicates a temporary event, not a durable frozen cover on the Arctic.

The study gives new light on the way in which the Arctic behaved in extreme conditions in the past. This counts because the Arctic changes quickly today. Knowing how the circulation of sea and ocean ice has reacted to past climate change helps scientists understand what might expect.

“These past models help us understand what is possible in future scenarios,” said Knies. “We must know how the Arctic behaves under stress – and what the tipping of points to be monitored – as the Arctic reacts to a warming world.”