Arctic Ocean began to warm decades earlier than previously thought, study indicates

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The Arctic Ocean has been warming since the early 20th century, decades earlier than instrumental observations would suggest, according to new research.

The study, published on Wednesday (25) in the journal Science Advances, found that the expansion of warming waters from the Atlantic Ocean that flow into the Arctic, a phenomenon known as “Atlantification,” caused the waters to rise in the region studied. at about 2 degrees Celsius since 1900.

Francesco Muschitiello, the study’s author and assistant professor of geography at Cambridge University, said the findings are worrying because early warming suggests there may be a flaw in the models scientists use to predict how the climate will change.

“The Arctic Ocean has been warming for a lot longer than we thought,” Muschitiello told CNN. “And that’s something that’s a little disturbing for a lot of reasons, especially since the climate models we use to make projections of future climate change don’t actually simulate this kind of change.”

The researchers used marine sediments in the Fram Straight, 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 flowed into the Arctic. Marine sediments are “natural archives”, wrote the researchers, which record data on past climatic conditions.

Researchers found that temperature and salinity, the salt of ocean water, remained fairly constant until the 20th century – then suddenly increased.

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

Muschitiello said it is unclear what role man-made climate change played in the early Arctic warming, and that more research was needed.

“We’re talking about the early 1900s, and by then we’ve 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 further research, of course, because we don’t have solid control over the real mechanisms behind this early Atlanticification.”

The study notes that changes in the Southern Atlantic Circulation (AMOC) – a system of currents that moderate temperatures in the northern hemisphere – may have played a role in warming the Arctic. Notably, the AMOC weakened after a cooling period that ended in the mid-1800s in the North Atlantic region, which researchers suggest may have led to rapid atlantification along the Fram Strait.

A recent study found that the AMOC, often described as a “conveyor belt” that transports hot water from the tropics and redistributes it northward, is now showing signs of further instability due to man-made climate change. Scientists have warned that a collapse in circulation could lead to an abrupt shift in weather patterns around the world – colder winters in Europe, changes in monsoons and potentially permanent droughts in West Africa.

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

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

“The loss of sea ice and ocean currents has shifted the buffer region between the Atlantic Ocean and the Arctic to something closer to an arm of the central Atlantic,” Overland, who did not participate in the study, told CNN. “Important fisheries and marine mammals are vulnerable to ecosystem reorganization from this Atlantis.”

A recent UN state of science report on the climate crisis concluded that the Arctic will continue to warm faster than the rest of the planet as long as humans continue to burn fossil fuels and release greenhouse gases into the atmosphere. In addition, Muschitiello said that the Arctic Ocean could experience further warming due to Atlanticification.

“When I talk to my students, I always try to alert them that the Arctic is warming up very, very quickly and much faster than any other area on the planet,” said Muschitiello. “It’s very disturbing and disturbing, especially since we still don’t fully understand the feedbacks at play.”

“We are still slowly learning how the whole system works,” he said. “And my fear is that when we solve the problem, it will be too late.”

* (Translated text. Click here to read the original).

Reference: CNN Brasil

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