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A massive current system in the Atlantic Ocean, which affects climate, sea level and weather systems around the world, could be on the verge of being fatally disrupted.
A new report published in the journal Nature Climate Change describes how a series of Atlantic Ocean currents have reached “an almost complete loss of stability over the past century” as the planet continues to warm. The report, written by Dr Niklas Boers, specifically analyzes data on the temperature and salinity of the oceans to show that their circulation has weakened in recent decades. If current trends continue unabated, they could slow down to a dangerous level or even stop altogether.
The series of currents in question is known as the Atlantic Meridional Reversal Circulation, or AMOC for short. The current system is sometimes compared to a series of conveyor belts: a “conveyor belt” flows north with hot water which, on reaching the North Atlantic, cools and evaporates, thus increasing the salinity. of water in this region. The saltier water becomes colder and heavier, sinking and flowing southwards to create a second “belt”. These two currents are in turn linked by other oceanic features in the Southern Ocean, Labrador Sea, and North Sea.
The study builds on previous scientific studies which found that the southern Atlantic overturning circulation system was at its weakest in 1,600 years.
This so-called treadmill system has been in place for thousands of years or more, and ocean life has adapted to its rhythms. Indeed, AMOC, which scientists say can slow down or turn off abruptly when temperatures rise, is also vital to sustaining humanity’s way of life. If it stops, the temperature will drop in Europe as the number of thunderstorms increases; changing weather conditions will lead to food shortages in South America, India and West Africa; and rising sea levels along the east coast of North America will force millions to flee their homes. Considering that AMOC is already starting to decline, this is a serious threat that could radically alter our planet in just a few decades.
“This decline may be associated with an almost complete loss of stability over the past century, and AMOC could be nearing a critical transition to its weak circulation pattern,” the analysis explains.
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This is not the first disturbing news that has emerged about AMOC. In February, another study found that AMOC could be weakened by 34% to 45% by the turn of the century as arctic ice and the Greenland ice sheet continue to melt. The new report, however, increases the growing sense of scientific concern over the integrity of AMOC.
“This work provides further support to our previous work in the same journal Nature Climate Change, suggesting that a climate change-induced slowdown in ‘conveyor belt’ ocean circulation already underway, decades ahead of schedule, a another reminder that uncertainty is not our friend, “Dr. Michael E. Mann, distinguished professor of atmospheric science at Penn State University, wrote in Salon.” There are surprises in store, and they are likely to happen. be rude about the climate crisis. “
Cristian Proistosescu, an assistant professor at the University of Illinois-Urbana-Champaign who studies climate dynamics and the consequences of global warming, was more measured in his assessment.
“If the worst-case scenario happens – and it’s a big if – we can certainly expect to see dramatic climate change in the far north of Europe,” Proistosescu told Salon via email. He described a world in which Scandinavian winters are no longer mild, where rainfall patterns shift south to central Africa, and other weather patterns change dramatically. Worst-case scenarios can be “somewhat improbable,” he added, noting that the majority of updated climate models predict gradual deterioration over the 21st century rather than a brutal showdown.
“The data we have is too short to say with any real certainty whether the collapse of the North Atlantic overturning circulation is really imminent,” Proistosescu concluded. “The question for me is how cautious should we be in the face of uncertainty and how much do we want to avoid a high cost, low probability disaster scenario? Considering the magnitude of the costs, we should be pretty risk averse. “
Not all climate experts are impressed with the new study’s findings. Kevin Trenberth, who is in the climate analysis section of the US National Center for Atmospheric Research, told Salon via email that the new report is “a bunch of total BS. They don’t refer to any of our posts. over the Atlantic and what’s going on there and they’ve got it all wrong. ” He added that based on “the best and longest[st] record they don’t have, the N[orth] The Atlantic is dominated by natural variability and they can’t say anything about longer term changes. “
US atmospheric scientist Ken Caldeira also warned of exaggerating the situation with AMOC. He wrote to Salon that “it should also be noted that paleoclimatic data indicates that a stop to circulation in the North Atlantic could have wider consequences than climate models predict.” The problem is that even our most sophisticated climate models don’t contain enough detail to be able to anticipate with certainty what’s going to happen in our climate system.
Like Proistosescu, Caldeira urged to err on the side of safety. “In this case, uncertainty means risk, and, because the effects of our CO2 emissions are indeed irreversible, this risk should warrant a high degree of caution,” he concluded.
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