For years, scientists have discussed whether the giant thick ice shelf once covered the entire Arctic Ocean during the coldest ice age. Now a new study published in Progress of scienceIt challenges this idea because the research team has not found evidence of the presence of a huge ice shelf of 1 KM. Instead, the Arctic Ocean seems to have been covered with seasonal marine ice-derivation of open waters and living conditions even during the most difficult periods of cold periods over the last 750,000 years. This discovery gives the insight key to our understanding of how the Arctic responded to climate change in the past – and that it could behave in the future.
Tiny traces of life in ancient mud
Led by the project of the European Research Council of Synergy Grant in Blue – I2B, the research team studied the cores of the sediment collected from the seabed of the Central Nordic Sea and the Yermak Plateau, north of Svalbard. These cores hold small chemical fingerprints from the algae that lived in the ocean long ago. Some of these algae only grow in open water, while others succeed under seasonal marine ice that forms and melts every year.
“Our sediment core shows that marine life was active even in the coldest times,” said Jochen Knies, a leading author of the study, headquartered at the UIT, the Arctic University of Norway and the Project co-head at Blue-I2B. “That tells us that on the surface he had to be light and open water. You wouldn’t see that if the whole Arctic was locked under the ice slab, miles thick.”
One of the key indicators that the team sought was a molecule called IP25produced by algae that live in seasonal sea ice. His regular appearance in sediments shows that the sea ice came and left with seasons, instead of staying frozen firmly throughout the year.
Simulating the ancient Arctic climate
In order to test the findings based on the geological records, the research team used the AWI Earth System-Budget model of high resolution-as it would simulate arctic conditions over two, especially cold periods: the last ice maximum about 21,000 years ago, and deeper freezing about 140,000 years ago, when large ice tiles covered many arctic.
“Models support what we found in sediments,” Knies said. “Even during these extreme glaciers, the warm Atlantic water continued to flow into the Arctic entrance. This helped that some parts of the ocean do not freeze completely.”
The models also showed that the ice is not static. Instead, she moved with seasons, creating openings in ice where light could reach the water – and where life could continue to progress. This study not only reminds our opinion of past Arctic climate, but also has consequences on future climate predictions. Understanding how the circulation of marine ice and ocean responded to past climate extremes can improve models that project future changes in the warming world.
“These reconstructions help us to understand what is possible, which is not-when it comes to the ice cover and the dynamics of the ocean,” said Gerrit Lohmann, co-authored by this study, headquartered at the Alfred Wegener Institute, Helmholtz Center for Polar and Marine Research (AWI) and Ko-Vitnja in Blue. “This is important when you try to predict how icy and marine ice can behave in the future.”
Re -thinking about giant theory of icy shelves
Some scientists claimed that features on the Arctic seabed suggest that it was a huge, grounded ice shelf once covered the entire ocean. But this new study offers another explanation.
“There may have been short -lived ice shelves in some of the Arctic during particularly strong cold stages,” Knies said. “But we do not see any sign of one, massive ice shelf that has covered everything for thousands of years.”
One possible exception could happen about 650,000 years ago, when biological activity in the sediment record fell sharply. But even then, the evidence indicates a temporary event, not a long frozen cover over the Arctic.
Understanding the future of the Arctic
The study casts new light on how the Arctic has acted in extreme conditions in the past. This is important because the Arctic is changing quickly today. Knowing that the circulation of marine ice and ocean responded to past climate change helps scientists understand what could be ahead.
“These past patterns help us to understand what is possible in future scripts,” Knies said. “We need to know how the Arctic behaves under stress – and at what points to be careful about – because the Arctic responds to the warming world.”
Whole paper, “Seasonal sea ice characterized the glacial arctic-atlantic entrance in the last 750,000 years, “ It is available in scientific progress.
This research is part of the Synergy Grant European Council for Research Project In blue – i2b and the Norwegian Center for Excellence Council, IC3: LED Center, Kriosphere, Carbon and Climate.
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