The circulation of currents in the Atlantic at its lowest level in 1,600 years

This slowdown could disrupt the climate in Europe and the United States ...

Modeling the Gulf Stream in the Atlantic Ocean. - Woods Hole Oceanographic Institution

The report worries scientists. The circulation of ocean currents in the Atlantic, which contribute to the regulation of the global climate, is at its lowest level in 1,600 years, partly because of climate change, warn researchers Wednesday. Two studies published in Nature validate the long-standing hypothesis of a weakening of the circulation of these currents known by the acronym AMOC (meridian circulation of turning of the Atlantic).

This weakening of the currents is the result of the melting of the pack ice, glaciers and ice shelves, which release fresh water, less dense than salt water, in the North Atlantic.

"Fresh water weakens AMOC because it prevents water from becoming dense enough to sink," says David Thornalley of University College London, co-author of one of the studies.

Rising sea level and storms

This permanent circulation of marine waters consists of a rise of warm waters from the tropical areas of the Atlantic to the North thanks to the Gulf Stream, warming the passage of Western Europe. Once in the North Atlantic, these waters cool, become denser and heavier, and sink under warmer waters to return to the south.

"If the system continues to weaken, it could disrupt weather conditions from the United States and Europe to the Sahel and cause a faster rise in sea levels on the east coast of the United States," warns Woods. Hole Oceanographic Institution, who participated in the research. If the trend continues, possible consequences would be more winter storms in Europe or a shift south of the rain belt.

15% slowdown in 50 years

These ocean currents also transport nutrients, oxygen, coral larvae or fish from one area to another. They also contribute to the ability of the oceans to absorb and store carbon dioxide (CO2), the main cause of global warming.

In the first study, David Thornalley and his team studied sand grains deposited by currents on the seabed over time. The larger the sand grains found in the sediments, the stronger the currents that transported them.

The results show that AMOC was relatively stable between the year 400 and 1850 and began to weaken at the beginning of the industrial era. The second study looked at ocean surface temperatures and concluded that AMOC has declined by about 15% in the last 50 years, probably because of climate change due to human activities.

The affected fishery

According to the European research fund ATLAS, which also participated in the studies, the commercial fishery could be affected by changes in the position and depth of ocean currents and some regions would lack oxygen-rich waters.

"A weakening of AMOC can also lead to temperature rises or falls of several degrees, affecting some important fish species (for humans), as well as the amount of plankton, fish, birds and fish. whales, "he said in a statement.

In addition, if the ocean currents are still losing strength, it would lead to "leaving more carbon dioxide in the atmosphere, where it contributes to global warming," says Thornalley, fueling the vicious circle.

SOME images and videos are used without the express authorisation of the copyright holders. They are used under what's known in British law as 'Fair Dealing' and under US law as 'Fair Use' exceptions. For example, exceptions relating to research and private study, criticism or review, or news reporting. For more information visit the UK Gov website https://www.gov.uk/guidance/exceptions-to-copyright#fair-dealing or the US Gov website https://www.copyright.gov/fls/fl102.html