The Atlantic currents in response to climate change are surged towards tipping points that could cause serious consequences by the end of this century, new research finds.
The current forms the Atlantic Meridian’s Coverage Circulation (AMOC), which loops around the Atlantic like a giant conveyor belt, bringing heat into the Northern Hemisphere before moving again south along the seabed. Depending on which carbon humans release in the next few decades, AMOC could reach a turning point, with dramatic results in some regions in 2055, researchers found.
This horrifying forecast is not thought to be based on a scenario where carbon emissions will double between now and 2050, but research shows that it is a result of a scenario where emissions around current levels over the next 25 years are far more likely to be less good. The latest UN Climate Report suggests that AMOC will begin to collapse in 2063, even if it keeps this century’s Fahrenheit (2.7 degrees Celsius) above 4.8 degrees Fahrenheit (2.7 degrees Celsius) in a (central road) scenario.
“The potential for chips is much greater than previously thought,” Sybren Drijfhout, a professor of physical oceanography at the University of Southampton in the UK and Utrecht in the Netherlands, told Live Science in an email. Overall, the chances of AMOC collapse this century are around 50-50 years old, and Drijfhout was not involved in new research, but he estimated that he led a similar study recently published in Journal Environment Research Letters.
In this study, Drijfhout and colleagues ran the latest climate models over 2100 and found that high emission scenarios, or scenarios that caused about 8 F (4.4 C) above pre-industrial levels by the end of this century, have always led to the collapse of AMOC. The scenario, which is consistent with the objectives of the Paris Agreement to maintain warming ideally below 2.7 F (1.5 c), also caused the collapse of the two models, and the breakdown, he said, is more likely than scientists had previously thought.
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Geophysical Research Journal: OCEANS, a new modeling study published in the climate model of TESTIMED 25 August, found indicators that help researchers determine when AMOC will reach a tipping point. Unlike parameters commonly used to monitor AMOCs indirectly, such as sea surface temperature, this new indicator is dominated by the dynamics of the Atlantic circulation.
Related: “We don’t think of it as a low probability anymore”: The collapse of the major Atlantic current can have devastating effects, says oceanographer Stephen Rahmstouff
Van Westen and colleagues have previously shown that freshwater flows in the Atlantic, 34 degrees south, latitude along the tip of South Africa, are a good marker of AMOC stability and can alert scientists to imminent collapse. The marker works to slowly change environmental conditions, but does not help identify trends in AMOC under rapidly warming climates, Van Westen said.
“Therefore, we were aiming to develop new indicators that would work even amid climate change,” he said.
New markers for AMOC strength
To measure that it reaches a tipping point, a new study examined masses of water sinking into the seabed of the North Atlantic Ocean.
Now surface water loses heat to the atmosphere when it reaches the cold North Atlantic Ocean. This surface water becomes extremely cold, salty and dense, sinking to the bottom of the ocean and forms a current that travels along the seabed into the southern hemisphere. The cold, dense subsidence process is called the deep sea layer, and it is the engine that drives the AMOC. Deep water formation can be measured by changing seawater density or extrapolating ocean data from climate models.
“If this amount is reduced to zero, it means the surface will become too light and no sinking occurs,” which is essentially the moment the AMOC begins to collapse.
The deep water layer has already decreased due to both the temperatures of the North Atlantic and the temperatures of the Arctic ice melt. Warm air means that surface water cannot lose enough heat to sink, but ice melts dilute the salt concentration of the water, thereby reducing its density.
Researchers have identified surface buoyancy flux, one component of deep water formation. This was a “shortcut” for estimating deep aquatic formations throughout the North Atlantic, Van Westen said. Surface buoyancy flux is a parameter that combines changes in sea surface heat and salinity to understand how these affect water density. Heat and salinity can be directly monitored using instruments or satellites, but in this study, we examined existing heat and salinity data in simulating sea surface dynamics.
“The advantages of [the surface buoyancy flux] That means you can calculate it with many climate models,” Van Westen said.
Van Westen said the surface buoyancy flux remained constant until 2020. This means that there was little change in AMOC before that. This is strengthened by research published in January.
However, since 2020, surface buoyancy flux has been increasing, suggesting that AMOC is weakening. The model showed that emission paths could cause earlier collapse of AMOCs than the “center of the road” emission paths, so research suggested that suppressing the use of fossil fuels was urgent.
“When following a low emissions scenario, there is a possibility that AMOC collapse scenarios can be prevented,” says Van Westen, which requires reaching net zero carbon emissions around 2050.
“Serious Climate Wake-up Call”
The AMOC collapse in the 2060s is “very worried” Drijfhout said, but the uncertainty is too high, identifying the exact year that AMOC collapses in different emission pathways to identify the exact year.
The outcome will be dramatic and global, but Europe will be hit particularly hard, Drijfhout said. The collapse of AMOC will result in much colder temperatures in northwestern Europe, and a reduction in precipitation, which could lead to agriculture losses of around 30%, he said. Winters in Europe are much harsher, with more storms and floods occur along the Atlantic coast due to redistribution of water around the ocean as AMOC slows down.
“We expect even greater sea level rise on the US East Coast,” Drijfhout said. It can also affect places that do not come into contact with the Atlantic Ocean. For example, the monsoon regions of Asia and Africa.
European Climate Commissioner Wopke Hoekstra is zero-zero and continues to grow cleanly, describing the findings as “a call for a serious climate awakening” in a social media post. “This new study states that Gulf tides could collapse in our lives,” he warned.
However, research shows that no impact is felt right after AMOC begins to collapse. The authors estimate that AMOC will be significantly weakened and it will take more than 100 years for new weather patterns to emerge.
However, Drijfhout believes that the collapse could occur for just 50 years. AMOC is like a campfire with reduced fuel volumes, he said. “If you stop throwing new wooden blocks over a fire, the fire won’t die anytime soon, but it’s smoldering for a while,” Drijfhout said. “For AMOC, this ‘smoldering time’ is [about] 50 years. ”
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