Global warming in polar regions could significantly disrupt ocean circulation patterns, a new study suggests. Scientists have found that, in the distant past, increasing influxes of fresh water from melting Arctic sea ice in the Nordic Seas likely significantly affected ocean circulation, causing temperatures in the northern Europe.
“Our finding that accelerated melting of Arctic sea ice likely led to significant cooling in Northern Europe in Earth’s past is alarming,” says Mohamed Ezat of the iC3 Polar Research Center, lead author of the study, available open access in Nature Communications.
“It reminds us that the planet’s climate is a delicate balance, easily disrupted by changes in temperature and ice cover. »
The Arctic Ocean is expected to be ice-free by the year 2050.
Earlier this month, dozens of climate scientists warned in an open letter that climate change poses a “serious risk of a major shift in Atlantic ocean circulation.” [qui] would have devastating and irreversible impacts.
The Nordic Seas, located between Greenland and Norway, are a key area for ocean heat transport and influence weather conditions far beyond their geographic boundaries.
During the early part of the last interglacial period, more than 100,000 years ago, global temperatures were warmer than today, ice volumes were smaller, and sea levels were significantly higher .
Mohammed Ezat’s research team has now linked global warming and the accelerated melting of Arctic sea ice around this time to changes in sea surface temperature and ocean circulation in the region.
Melting sea ice changed the salinity and density of water and disrupted the normal flow of currents, leading to changes in circulation patterns and heat distribution across the ocean.
Understanding the dynamics of the last interglacial is crucial, he explains. Past warm periods in Earth’s history highlight the importance of feedback mechanisms in the climate system. As the Arctic continues to warm and sea ice decreases, further changes to ocean currents and weather patterns could occur.
Ezat’s research team used a combination of biological, inorganic and organic geochemical tracers from sediment cores collected in the Nordic Seas. These cores act like time capsules, preserving information about past ocean conditions. By analyzing chemical signatures in these sediments, the team was able to reconstruct past sea surface temperatures and salinity levels, sources of freshwater input, and deep water formation processes.
Mohamed Ezat warns that many questions still remain unanswered. “We can learn a lot from the still open question of the last interglacial cooling in the Norwegian Sea and the potential responsible processes,” he says. “We hope our study provides a reference point for climate modelers to use this period to better limit the impacts of ice changes on regional and global climate.” »
The study used a multi-proxy approach (diatom, dinocyst and planktic foraminifera assemblages, sea ice biomarkers, planktic Na/Ca and Ba/Ca foraminifera, and benthic foraminifera assemblages) to reconstruct the evolution of sea ice, sea surface temperature, deep ocean convection, and changes in freshwater input and sources during the last interglacial period.
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