Key Atlantic current could start collapsing as early as 2055, new study finds
The current ocean currents that respond climate change rush to a tilting point which could cause serious impacts before the end of this century, according to a new study.
The currents are those which form the circulation of southern Atlantic (AMOC), which loops around the Atlantic Ocean as a giant treadmill, bringing heat to the northern hemis before moving to the south along the seabed. Depending on the quantity of carbon that humans emit in the coming decades, the Amoc could reach a tilting point and start to collapse in 2055, with dramatic consequences For several regions, the researchers have discovered.
This frightening prediction, based on a Scenario where carbon programs double By 2050, is considered to be unlikely – but the result of a much more likely scenario where emissions hover around current levels for the next 25 years are not much better, depending on the study. Even if we keep global warming this century at 4.8 degrees Fahrenheit (2.7 degrees Celsius) above the pre -industrial levels – a scenario of “middle of the road”, according to the Last report of the United Nations climate – The Amoc will begin to collapse in 2063, suggest the results.
“The chances of switching are much larger than you thought before,” Sybren DrijfhoutProfessor of physical oceanography at the University of Southampton in the United Kingdom and the University of Utrecht in the Netherlands, said in Live Science in an email. Overall, the chance to collapse the Amoc This century is around 50-50, Drijfhout, which was not involved in the new research but recently conducted a similar study published in the journal Environmental research lettersestimates.
In the study, Drijfhout and his colleagues directed the last climate models for a period extending beyond 2100 and found that the high-program scenarios, or those which cause approximately 8 F (4.4 C) of warming above pre-industrial levels by the end of this century, have always led to an Amoc collapse. Scenarios that aligned themselves on the goal of Paris Agreement To continue to warm up ideally below 2.7 F (1.5 C), also triggered a collapse in two of the models, which suggests that a breakdown is more likely than scientists thought previously, he said.
The new modeling study, published on August 24 in the Journal of Geophysical Research: OceansTested 25 climate models and found an indicator that helped researchers determine when the Amoc could reach a tilting point. Unlike the parameters commonly used to indirectly monitor the AMOC, such as the temperature of the sea surface, this new indicator is governed by the dynamics of the Atlantic Ocean circulation, the main author of the study René Van WestenA postdoctoral researcher in climate physics at the University of Utrecht, told Live Science in an email.
In relation: “ We no longer really consider it, a low probability ”: the collapse of the key Atlantic current could have catastrophic impacts, explains the oceanographer Stefan Rahmstorf
Van Westen and his colleagues have previously shown that the flow of the Atlantic’s fresh water at 34 degrees in the south, latitude along the tip of South Africa, is a Good marker of the stability of the Amoc And can warn scientists from an imminent collapse. This marker works for slowly evolving environmental conditions, but it is less useful for identifying AMOC trends in a rapid warming climate, Van Westen said.
“Therefore, we aimed to develop a new indicator that also works under climate change,” he said.
A new marker for AMOC Force
To assess when tilting points are reached, the new study has examined the mass of water flowing at the bottom of the ocean in the North Atlantic.
Currently, surface water loses heat in the atmosphere when it reaches the cold of the North Atlantic. This surface water becomes so freezing, salty and dense that it flows at the bottom of the ocean, forming currents that travel along the bottom of the ocean to the southern hemisphere. The cold and dense shipwreck process is called deep water formation, and it is the engine that causes the Amoc. The formation of deep waters can be measured by changes in seawater density or by extrapolating oceanic data in climate models.
“When this quantity reduces to zero, this means that the surface has become too light and that no sinking takes place”, which is essentially the moment when the Amoc begins to collapse, said Van Westen.
Deep water formation is already down due to warming air temperature in the North Atlantic and the melting of Arctic ice. Hot air means that surface water cannot lose enough heat to flow, while the melting of ice dilutes the concentration of salt from the water and thus decreases its density.
The researchers identified a component of the formation of deep waters, the surface burst flow, which was a “shortcut” to estimate the formation of deep water across the North Atlantic, said Van Westen. The surface burst flow is a parameter that combines heat and salinity changes on the surface of the ocean to understand how they have an impact on water density. Heat and salinity can be monitored directly using instruments or satellites, but the study has examined the existing heat and salinity data in the dynamics of the sea surface, the surface burst flowing in different models and experiences as a clear marker of the AMOC force.
“The advantage of [the surface buoyancy flux] is that it can be calculated in many climate models, “said Van Westen.
The surface burst flow was constant until 2020, said Van Westen, which means that there have been no changes in the Amoc before that – a conclusion that Rendered by research published in January.
Since 2020, however, the surface burst has increased, suggesting that the Amoc weakens. The models have shown that high -emission paths could trigger an anterior collapse of the AMOC that the emission paths “In the middle of the road”, it is therefore urgent to slow down the use of fossil fuels, according to the study.
“A Amoc collapse scenario can possibly be avoided during the continuation of a weak emission scenario,” said Van Westen, but this would require reaching zero net carbon emissions around 2050.
An “serious climate awakening”
A collapse of the Amoc in the 2060s is plausible and “very worrying”, said Drijfhout, but the uncertainties are too large to identify precise years when the Amoc collapsed under different paths of issue.
The consequences would be dramatic and global, but Europe would be particularly affected, said Drijfhout. A collapse of the AMOC would lead to much cooler temperatures in North West Europe, as well as a decrease in precipitation which could cause agricultural losses by around 30%, he said. The winters in Europe would be much harder, with more storms and floods along the Atlantic coast resulting from a redistribution of water around the ocean while the Amoc slows down.
“”We can expect an even larger sea level increase On the coasts is American “because of this redistribution, Drijfhout said. And the places that are not lined with the Atlantic could also be affected, Like the regions of monsoon in Asia and Africahe said.
Wopke HoekstraThe European climate commissioner, the net zero and the own growth, described the conclusions as a “alarm clock of the serious climate” in a Social media message. “This new study indicates that Gulf Stream could collapse in our life,” he warned.
However, the effects will not be felt immediately after the Amoc begins to collapse, according to the study. The authors believe that it would take more than 100 years for the Amoc to weaken considerably and that new weather conditions emerge.
But Drijfhout thinks that the collapse could occur over only 50 years. The Amoc is like a campfire with a reduction in fuel, he said. “If we stop throwing new wooden blocks on the fire, the fire will not die immediately, but it continues to flow for a while,” said Drijfhout. “For the Amoc, this” melting time “is [about] 50 years. “”
