(Press-News.org) For years, scientists have debated whether a giant thick ice shelf once covered the entire Arctic Ocean during the coldest ice ages. Now a new study published in Science Advances, challenges this idea as the research team found no evidence for the presence of a massive ~1km ice shelf. Instead, the Arctic Ocean appears to have been covered by seasonal sea ice—leaving open water and life-sustaining conditions even during the harshest periods of cold periods during the last 750,000 years. This discovery gives insights crucial for our understanding of how the Arctic has responded to climate change in the past—and how it might behave in the future.
Tiny traces of life in ancient mud
Led by the European Research Council Synergy Grant project Into the Blue – i2B, the research team studied sediment cores collected from the seafloor of the central Nordic Seas and Yermak Plateau, north of Svalbard. These cores hold tiny chemical fingerprints from algae that lived in the ocean long ago. Some of these algae only grow in open water, while others thrive under seasonal sea ice that forms and melts each year.
“Our sediment cores show that marine life was active even during the coldest times,” said Jochen Knies, lead author of the study, based at UiT The Arctic University of Norway and co-lead of the Into The Blue - i2B project. “That tells us there must have been light and open water at the surface. You wouldn’t see that if the entire Arctic was locked under a kilometre-thick slab of ice.”
One of the key indicators the team looked for was a molecule called IP25, which is produced by algae that live in seasonal sea ice. Its regular appearance in the sediments shows that sea ice came and went with the seasons, rather than staying frozen solid all year round.
Simulating ancient Arctic climates
To test the findings based on the geological records, the research team used the AWI Earth System Model – a high-resolution computer model – to simulate Arctic conditions during two especially cold periods: the Last Glacial Maximum around 21,000 years ago, and a deeper freeze about 140,000 years ago when large ice sheets covered a lot of the Arctic.
“The models support what we found in the sediments,” said Knies. “Even during these extreme glaciations, warm Atlantic water still flowed into the Arctic gateway. This helped keep some parts of the ocean from freezing over completely.”
The models also showed that the ice wasn’t static. Instead, it shifted with the seasons, creating openings in the ice where light could reach the water—and where life could continue to thrive. This research not only reshapes our view of past Arctic climates but also has implications for future climate predictions. Understanding how sea ice and ocean circulation responded to past climate extremes can improve models that project future changes in a warming world.
“These reconstructions help us understand what’s possible—and what’s not—when it comes to ice cover and ocean dynamics,” said Gerrit Lohmann, co-author of this study, based at Alfred Wegener Institute, Helmholtz Centre for Polar and Marine Research (AWI) and co-lead of Into The Blue – i2B. “That matters when trying to anticipate how ice sheets and sea ice might behave in the future.”
Re-thinking the giant ice shelf theory
Some scientists have argued that features on the Arctic seafloor suggest that 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 parts of the Arctic during especially severe cold phases,” said Knies. “But we don’t see any sign of a single, massive ice shelf that covered everything for thousands of years.”
One possible exception could have occurred about 650,000 years ago, when biological activity in the sediment record dropped sharply. But even then, the evidence points to a temporary event, not a long-lasting frozen lid over the Arctic.
Understanding the Arctic’s future
The study sheds new light on how the Arctic has behaved under extreme conditions in the past. This matters because the Arctic is changing rapidly today. Knowing how sea ice and ocean circulation responded to past climate shifts helps scientists understand what might lie ahead.
“These past patterns help us understand what’s possible in future scenarios,” said Knies. “We need to know how the Arctic behaves under stress—and what tipping points to watch for – as the Arctic responds to a warming world.”
The full paper, “Seasonal sea ice characterized the glacial Arctic–Atlantic gateway over the past 750,000 years”, is available in Science Advances.
This research is part of the European Research Council Synergy Grant project Into the Blue – i2B and the Research Council of Norway Centre of Excellence, iC3: Centre for ice, Cryosphere, Carbon, and Climate.
END
Imagine the magnificent glaciers of Greenland, the eternal snow of the Tibetan high mountains, and the permanently ice-cold groundwater in Finland. As cold and beautiful these are, for the structural biologist Kirill Kovalev, they are more importantly home to unusual molecules that could control brain cells’ activity.
Kovalev, EIPOD Postdoctoral Fellow at EMBL Hamburg’s Schneider Group and EMBL-EBI’s Bateman Group, is a physicist passionate about solving biological problems. He is particularly hooked by rhodopsins, a group of colourful proteins that enable aquatic microorganisms to harness ...
Gut bacteria are known to be a key factor in many health-related concerns. However, the number and variety of them is vast, as are the ways in which they interact with the body’s chemistry and each other. For the first time, researchers from the University of Tokyo used a special kind of artificial intelligence called a Bayesian neural network to probe a dataset on gut bacteria in order to find relationships that current analytical tools could not reliably identify.
The human body comprises about 30 trillion to 40 trillion cells, but your intestines contain about 100 trillion gut bacteria. Technically, you’re carrying around more cells that aren’t ...
The peer-reviewed study, The Earth4All Scenarios: Human Wellbeing on a Finite Planet Towards 2100, uses a system dynamics-based modelling approach to explore two future scenarios: Too Little Too Late, and the Giant Leap. The model presented in the paper provides the scientific basis for the analysis and policy recommendations of Earth for All: A Survival Guide for Humanity, published in 2022.
The model’s findings show that under our current ‘business as usual’ conditions – the Too Little Too Late scenario – ...
Villages, often separated from larger towns and cities, consist of clusters of households and a few public buildings. Despite their long history, the biodiversity of European villages has been understudied compared to urban areas, forests, grasslands, or agricultural fields. A new study reveals their biodiversity potential and how nearby landscapes influence biodiversity patterns and human well-being.
This research was led by an international team from the HUN-REN Centre for Ecological Research with 20 other institutes contributing from Hungary, Romania, Germany, and Italy. Published in Nature Sustainability, ...
As hydrogen infrastructure is rolled out in the EU, refuelling stations must be distributed according to the same principle in all countries. But now a study from Chalmers University of Technology in Sweden points to shortcomings in EU regulations. Using an advanced model, the researchers show that the distribution of refuelling stations may both be incorrectly dimensioned and lead to losses of tens of millions of euros a year in some countries.
By 2030, EU countries must have built hydrogen refuelling stations at least every ...
Children born by planned C-section have an increased risk of developing acute lymphoblastic leukaemia (ALL) later in life. This is shown by a study conducted by researchers at Karolinska Institutet. The researchers emphasise that the risk remains low.
The study, published in The International Journal of Cancer, covers nearly 2.5 million children born in Sweden during two periods, 1982 to 1989 and 1999 to 2015. Of these, 15.5 per cent were born by C-section, i.e. nearly 376,000 children. In the entire group, 1,495 children later developed leukaemia.
Using the Medical Birth Register, the ...
People who have survived cancer as children are at higher risk of developing severe COVID-19, even decades after their diagnosis. This is shown by a new study from Karolinska Institutet published in the journal The Lancet Regional Health – Europe.
Thanks to medical advances, more and more children are surviving cancer. However, even long after treatment has ended, health risks may remain. In a new registry study, researchers investigated how adult childhood cancer survivors in Sweden and Denmark were affected by the COVID-19 pandemic.
The ...
New research has revealed alarming coral mortality rates of 92 per cent after last year’s bleaching event at Lizard Island on Queensland’s Great Barrier Reef, marking one of the highest coral mortality rates ever documented globally.
The team assessed the impact of the Fourth Global Coral Bleaching Event, declared by the National Oceanic and Atmospheric Administration (NOAA) in April 2024, which caused extensive bleaching and mortality across the reef system.
Lead author Dr Vincent Raoult from Griffith University’s School of Environment, ...
Researchers at Zhejiang University School of Medicine have identified a single point mutation in the normal PML gene that can block the effect of arsenic trioxide, a frontline drug for acute promyelocytic leukemia. This discovery uncovers a hidden cause of treatment failure and suggests a new target for genetic screening in relapsed patients. This work addresses the urgent issue of why some patients relapse despite a therapy that otherwise greatly improves survival.
Mutation Explains Why a Small Portion of Leukemia Patients Relapse on Arsenic Therapy
Arsenic trioxide cures most acute promyelocytic leukemia patients, but some patients relapse without an ...
The future of smashed avocado might depend on patches of native vegetation preserved alongside farmland, as new Curtin research reveals the hidden role of these habitats in supporting the insects that keep crops - and brunch menus - thriving.
The research, published this week, found that insect communities in avocado orchards adjacent to native remnant vegetation foraged on more than twice as many plant species at times when crop flowering was limited, compared to those in orchards bordered by pasture.
Insects with more diverse food sources are more likely to survive and pollinate crops so this finding offers a potential clue to safeguarding ...