The changing climate in the polar areas may cause notable alterations in ocean circulation patterns, suggests a recent study. Researchers found that in the ancient past, increasing flows of freshwater from melting Arctic sea ice into the Nordic Seas likely had a major impact on ocean circulation, leading to a drastic drop in temperatures throughout northern Europe.
“Our discovery that increased melting of Arctic sea ice likely led to significant cooling in northern Europe during previous eras is concerning,” comments Mohamed Ezat from the iC3 Polar Research Hub, who is the lead author of the study. “This serves as a reminder that the Earth’s climate is a finely tuned equilibrium, easily disturbed by variations in temperature and ice presence.”
It is anticipated that the Arctic Ocean will experience ice-free summers starting from 2050.
Earlier this month, a group of climate scientists issued an open letter warning that climate change poses a “serious threat of a significant ocean circulation change in the Atlantic [that] could lead to catastrophic and irreversible consequences.”
The Nordic Seas, situated between Greenland and Norway, are crucial for ocean heat transport and have a considerable effect on weather systems far beyond their location.
During the early phase of the Last Interglacial, over 100,000 years ago, the Earth experienced warmer global temperatures, reduced ice volumes, and notably higher sea levels.
Mohamed Ezat’s research team has now connected the warming climate and increased melting of Arctic sea ice during that time to shifts in regional sea surface temperatures and patterns of ocean circulation.
As the sea ice melted, it changed the salinity and density of the ocean water, disrupting normal current flows, which in turn altered circulation and heat distribution in ocean waters.
Understanding the dynamics of the Last Interglacial is essential, he emphasizes. Historical warm periods illustrate the critical role of feedback mechanisms in the climate system. As the Arctic warms and ice diminishes, it may lead to further changes in ocean currents and weather patterns.
Ezat’s team utilized a range of biological and geochemical tracers from sediment cores collected from the Nordic Seas. These cores serve as time capsules that store information about previous ocean conditions. By examining the chemical clues in these sediments, the researchers could recreate earlier sea surface temperatures, salinity levels, sources of freshwater influx, and processes of deep water formation.
Mohamed Ezat warns that many questions remain unresolved. “There’s still much to learn about the factors behind the cooling during the Last Interglacial in the Norwegian Sea,” he states. “We hope our study serves as a reference point for climate modelers to analyze this period more thoroughly to better assess the effects of changing ice on regional and global climates.”
The study employed a multi-proxy technique, including diatom, dinocyst, and planktic foraminiferal assemblages, sea ice biomarkers, planktic foraminiferal Na/Ca and Ba/Ca, as well as benthic foraminiferal assemblages, to reconstruct the evolution of sea ice, sea surface temperatures, deep ocean convection, and shifts in freshwater contributions and their sources during the Last Interglacial epoch.
