The Arctic Ocean has been getting warmer since the beginning of the 20th century – decades earlier than records suggest – due to warmer water flowing into the delicate polar ecosystem from the Atlantic Ocean.
The rapid expansion of the Atlantic Ocean into the Arctic Ocean represents indisputable evidence of the rapid changes occurring in this region.
This so-called “Atlantification” of the Arctic Ocean has caused Arctic water temperature in the region studied to increase by around 2 degrees Celsius since 1900, according to a new study published in the journal Science Advances on November 24, 2021.
Francesco Muschitiello, a co-author of the study and assistant professor of geography at the University of Cambridge, said the findings were worrisome because the early warming suggests there might be a flaw in the models scientists use to predict how the climate will change.
“The Arctic Ocean has been warming up for much longer than we previously thought,” Muschitiello told CNN. “And this is something that’s a bit unsettling for many reasons, especially because the climate models that we use to cast projections of future climate change do not really simulate these types of changes.”
The international team of researchers came to this conclusion after reconstructing 800 years of data from marine sediments in the Fram Strait, where the Atlantic meets the Arctic east of Greenland.
The precisely dated paleoceanographic records they used were based on organic biomarkers and benthic foraminiferal data. The marine sediments are “natural archives,” the researchers wrote, which record data on past climate conditions.
The results the team came up with show the Arctic Ocean began to warm rapidly at the beginning of the last century, and that this change likely preceded the warming documented by modern instrumental measurements, with records that only go back about 40 years.
During the study, the researchers found that temperature and salinity, the saltiness of ocean water, remained fairly constant for the Arctic Ocean up until the 20th century. Since 1900, the ocean temperature has risen by approximately 2 degrees Celsius, while sea ice has retreated and salinity has increased, according to Phys.org.
“The reason for this rapid Atlantification of at the gate of the Arctic Ocean is intriguing,” said Muschitiello. “We compared our results with the ocean circulation at lower latitudes and found there is a strong correlation with the slowdown of dense water formation in the Labrador Sea.”
“In a future warming scenario, the deep circulation in this subpolar region is expected to further decrease because of the thawing of the Greenland ice sheet. Our results imply that we might expect further Arctic Atlantification in the future because of climate change.”
So what does this study have to do with the accuracy of today’s climate models? The researchers say the study may also expose a possible flaw in climate models because they do not reproduce this early Atlantification at the beginning of the last century.
Climate simulations generally do not reproduce this kind of warming in the Arctic Ocean, meaning there’s an incomplete understanding of the mechanisms driving Atlantification,” said Tommaso. “We rely on these simulations to project future climate change, but the lack of any signs of an early warming in the Arctic Ocean is a missing piece of the puzzle.”
