• Tue. Dec 7th, 2021

The Arctic Ocean started warming decades earlier than previously thought, new research shows


Nov 24, 2021

(CNN) – The Arctic Ocean has been warming since the early 1900s, decades earlier than instrument observations suggested, according to new research.
The study, published Wednesday in the journal Science Advances, found that the expansion of warm water from the Atlantic Ocean flowing into the Arctic, a phenomenon known as “atlantification,” has caused the temperature of Arctic water to rise in the region studied in around 2 ° C since 1900.

Icebergs in the Arctic Ocean off the Tierra de Francisco José archipelago on August 16, 2021.

Francesco Muschitiello, author of the study and associate professor of geography at the University of Cambridge, said the results were concerning because early warming suggests there could be a flaw in the models that scientists use to predict how the climate will change.

“The Arctic Ocean has been warming much longer than previously thought,” Muschitiello told CNN. “And this is something that is a bit unsettling for many reasons, especially since the climate models that we use to make projections of future climate change do not really simulate these kinds of changes.”

The researchers used marine sediments in the Fram Strait, where the Atlantic meets the Arctic east of Greenland, to reconstruct 800 years of data that paint a longer historical picture of how water from the Atlantic has flowed into the Arctic. Marine sediments are “natural archives,” the researchers wrote, recording data on past weather conditions.

The researchers found that the temperature and salinity remained fairly constant until the 20th century, then suddenly increased.

“The reconstructions suggest a substantial increase in the transport of heat and salt from the Atlantic Ocean to the Nordic Sea in the early 20th century, which is not well simulated by (climate models),” Rong Zhang, lead scientist at the Laboratory, told CNN. Geophysical Fluid Dynamics Department, which was not involved in the study. “It is important to understand the cause of this rapid atlantization, as well as the discrepancies between the model simulations and the reconstructions.”

The Strait of Fram is the place where the Atlantic Ocean and the Arctic converge.

Muschitiello said it is unclear what role, if any, human-caused climate change played in the early warming of the Arctic, and that more research is needed.

“We are talking about the early 20th century, and by then we had already overloaded the atmosphere with carbon dioxide,” he said. “It is possible that the Arctic Ocean is more sensitive to greenhouse gases than previously thought. This will require more research, of course, because we do not have a solid control of the real mechanisms behind this early Atlanticization.”

The study notes that changes in the Atlantic Southern Overturning Circulation (AMOC) – a system of currents that moderates temperatures in the northern hemisphere – may have played a role in warming the Arctic. In particular, the AMOC weakened after a cooling period that ended in the mid-19th century in the North Atlantic region, which the researchers said could have led to rapid Atlanticization along the eastern Strait of Fram.

According to a recent study, the AMOC, often described as a “conveyor belt” that carries hot water from the tropics and redistributes it northward, is now showing signs of increased instability due to human-caused climate change. Scientists have warned that a collapse in circulation could cause an abrupt change in weather patterns around the world: colder winters in Europe, changes in monsoons and a possible permanent drought in West Africa.

Rapidly warming temperatures in the Arctic have caused sea ice to melt, which in turn causes further warming: while bright white sea ice reflects energy from the sun, the dark ocean absorbs energy in form of heat.

James E. Overland, a NOAA Arctic scientist based at the Pacific Marine Environment Laboratory in Seattle, said these long-term changes in the North Atlantic, along with the recent loss of sea ice in the Arctic, threaten ecosystems. marine.

“The loss of sea ice and ocean currents has shifted the buffer region between the Atlantic and the Arctic Ocean to something more like an arm of the central Atlantic,” said Overland, who was not involved in the study. “Important fisheries and marine mammals are vulnerable to the reorganization of the ecosystem due to this atlantification.”

A recent UN report On the state of the science on the climate crisis, he concluded that the Arctic will continue to warm faster than the rest of the planet as humans continue to burn fossil fuels and release greenhouse gases into the atmosphere.

Additionally, Muschitiello said that the Arctic Ocean may experience further warming due to atlantification.

“When I talk to my students I always try to make them aware that the Arctic is warming very, very quickly, and much faster than any other area on the planet,” Muschitiello said. “It is very disturbing and very worrying, especially since we still don’t have a full understanding of what is at stake.”

“We are still getting to know little by little how the whole system works,” he said. “And my fear is that by the time we figure out the problem, it will be too late.”

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