The circulation in the Atlantic Ocean that underpins the Gulf Stream, the weather system that brings warm and mild weather to Europe, is at its weakest in more than a millennium, and according to new data, climate change is the likely cause.
A further weakening of the Atlantic Meridional Overturning Circulation (AMOC) could result in more storms plaguing the UK, more intense winters and an increase in damaging heatwaves and droughts across Europe.
Scientists predict that the AMOC will weaken further if global warming continues, and could decline by about 34% to 45% by the end of this century, bringing us close to a “tipping point” where the system is irreversibly unstable. could become. A weakened Gulf Stream would also raise sea levels on the US Atlantic coast, with potentially catastrophic consequences.
Stefan Rahmstorf, of the Potsdam Institute for Climate Impact Research, who co-authored the study published Thursday in Nature Geoscience, told the Guardian that a weakening AMOC would increase the number and severity of storms in Britain and would bring more heat waves to Europe.
He said blood circulation had already slowed by about 15% and the effects were visible. “In 20 to 30 years it will probably weaken further, and that will inevitably affect our weather, so we would see an increase in storms and heat waves in Europe, and sea level rise on the US East Coast,” he said.
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Rahmstorf and scientists from Maynooth University in Ireland and University College London in the UK concluded that the current weakening had not been observed in the past 1,000 years, after examining sediments, Greenland ice cores and other proxy data that revealed previous weather patterns about it. time. The AMOC has only been measured directly since 2004.
The AMOC is one of the world’s largest ocean circulation systems and carries warm surface water from the Gulf of Mexico to the North Atlantic Ocean where it cools and becomes saltier until it sinks north of Iceland, which in turn carries more warm water from the Caribbean area. This circulation is accompanied by winds that also help bring mild and wet weather to Ireland, the UK and other parts of Western Europe.
Scientists have long predicted a weakening of the AMOC as a result of global warming, and have expressed concern that it could collapse altogether. The new study found that such a point would likely be decades away, but persistently high greenhouse gas emissions would bring it closer.
Rahmstorf said, “We risk triggering [a tipping point] in this century, and circulation would decline within the next century. It is extremely unlikely that we have already activated it, but if we don’t stop global warming, it becomes more and more likely that we will activate it.
“The consequences of this are so great that even a 10% chance of causing a failure would be an unacceptable risk.”
Research in 2018 also showed a weakening of the AMOC, but the paper in Nature Geoscience says this was unprecedented in the past millennium, a clear indication that human action is to blame. Scientists have previously said that a weakening of the Gulf Stream could cause frigid winters in Western Europe and unprecedented changes across the Atlantic.
The AMOC is a large part of the Gulf Stream, often described as the “conveyor belt” that carries warm water from the equator. But the larger weather system wouldn’t completely break down if ocean circulation became unstable, as winds also play a key role. Circulation has been aborted before, under different circumstances, for example at the end of the last ice age.
The Gulf Stream is separate from the jet stream that has contributed to bringing extreme weather to the Northern Hemisphere in recent weeks, but like the jet stream, it is also affected by rising temperatures in the Arctic. Normally, the very cold temperatures over the Arctic create a polar vortex that keeps a constant jet of air currents that hold that cold air in place. But higher temperatures over the Arctic have resulted in a weak and wandering jet stream, causing the cold weather to spread much further south in some cases, while in others bringing warmer weather further north, adding to the extreme weather conditions in the UK. Europe and the US in recent weeks.
Likewise, the Gulf Stream is affected by the melting of polar ice, which dumps large amounts of cold water to southern Greenland, disrupting the flow of the AMOC. The effects of variations in the Gulf Stream are seen over much longer periods than variations in the jet stream, but will also entail more extreme weather as the climate warms.
The weakening of the AMOC would not only cause more extreme weather in Europe and the East Coast of the US, but could also have serious consequences for the Atlantic marine ecosystems, disrupting fish populations and other marine life.
Andrew Meijers, deputy scientific leader of the polar oceans at British Antarctic Survey, who was not involved in the study, said: “The AMOC has a major impact on the global climate, particularly in North America and Europe, so this is evidence of a continued weakening of circulation is crucial new evidence for the interpretation of future projections of regional and global climate.
“The AMOC is often modeled with a tipping point below a certain circulation strength, a point at which the relatively stable falling circulation becomes unstable or even collapses. The continued weakening of the tilt puts us at risk of finding that point, which would have major and probably irreversible consequences for the climate. “
Karsten Haustein, of the Climate Services Center in Germany, also independent of the study, said the US is at risk of stronger hurricanes due to the weakening Gulf Stream.
“While the AMOC will not collapse anytime soon, the authors warn that the flow could become unstable by the end of this century if warming continues unabated,” he said. “It has already increased the risk of stronger hurricanes on the east coast of the US as a result of warmer ocean waters, as well as possibly changing circulation patterns over Western Europe.”