Tides alter the amount of ice in the Arctic Ocean.  (Photo: Getty Images)

The Arctic Ocean has been warming since the early 1900s, decades earlier than records suggest, due to warmer water flowing into the polar ecosystem from the Atlantic Ocean.

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An international group of researchers has now reconstructed the recent history of ocean warming at the gateway to the Arctic Ocean, in a region called Strait of Fram, between Greenland and Svalbard.

Using chemical signatures found in marine microorganisms, the researchers discovered that the Arctic Ocean began to warm rapidly at the beginning of the last century as warmer and saltier waters flowed from the Atlantic – a phenomenon called Atlantification – and that this change likely preceded the warming documented by modern instrumental measurements.

Since 1900, ocean temperatures have risen by about 2 degrees Celsius, while sea ice has receded and salinity has risen, the authors note.

The results, published in the magazine ‘Science Advances‘, offer the first historical perspective of the Atlanticization of the Arctic Ocean and reveal a connection with the North Atlantic much stronger than previously thought.

This connection may influence Arctic climate variability, which could have major repercussions on retreating sea ice and rising sea levels on a global scale as polar ice caps continue to melt.

All the world’s oceans are warming due to climate change, but the Arctic Ocean, the smallest and shallowest of the world’s oceans, is the fastest warming of all.

“The rate of warming in the Arctic is more than double the world average, due to feedback mechanisms,” explains Dr. Francesco Muschitiello, co-author of the study and member of the Department of Geography at the University of Cambridge (UK) -. From satellite measurements, we know that the Arctic Ocean has been warming steadily, particularly in the last 20 years, but we wanted to put the recent warming in a longer context. “.

Atlantisation is one of the causes of global warming Arctic, but instrumental records capable of controlling this process, such as satellites, only date back about 40 years.

To the extent that Arctic Ocean Heats up, causing the ice in the polar region to melt, which in turn affects the global sea level. As the ice melts, more of the ocean is exposed to the sun, releasing heat and increasing the air temperature. As the Arctic continues to warm, permafrost, which stores huge amounts of methane, a greenhouse gas far more damaging than carbon dioxide, will melt.

The researchers used geochemical and ecological data from ocean sediments to reconstruct the changing properties of the water column over the past 800 years. They accurately date sediments using a combination of methods and look for diagnostic signs of atlantization, such as changes in temperature and salinity.

Tides alter the amount of ice in the Arctic Ocean. (Photo: Getty Images)

“When we look at the entire 800-year time scale, our temperature and salinity records seem fairly constant,” says Dr. Tesi Tommaso, co-author of the Institute of Polar Sciences of the National Research Council of Bologna (Italy) -. But suddenly, at the beginning of the 20th century, there is this marked change in temperature and salinity, which really attracts attention ”.

“The reason for this rapid Atlantisation of at the door of the Arctic Ocean It’s intriguing, ”explains Muschitiello. We compared our results with ocean circulation at lower latitudes and found that there is a strong correlation with the slowing of dense water formation in the Labrador Sea. “.

Anticipate that “In a future warming scenario, the deep circulation in this subpolar region is expected to decrease further due to the melting of the Greenland ice sheet. Our results imply that we could expect a further atlantisation of the Arctic in the future due to climate change “, Add.

The researchers claim that their results also expose a possible flaw in climate models, as they do not reproduce this early Atlanticization at the beginning of the last century.

“Climate simulations generally do not reproduce this type of warming in the Arctic Ocean, which means that there is an incomplete understanding of the mechanisms that drive Atlantification,” says Tommaso. We rely on these simulations to project future climate change, but the lack of any signs of warming early in the Arctic Ocean it’s a missing piece of the puzzle “.

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