The circulation of the Atlantic Ocean that underlies the Gulf Stream, the weather system that brings warm and mild weather to Europe, is the weakest in more than a millennium, and climate degradation is the likely cause, according to new data.
A further weakening of the South Atlantic’s twisted circulation (AMOC) could result in more storms beating the UK, more intense winters and an increase in heat waves and harmful droughts across Europe.
Scientists predict that AMOC will weaken further if global warming continues and could reduce by about 34% to 45% by the end of this century, which could bring us closer to a “tipping point” where the system it could become irrevocably unstable. A weakened gulf flow would also raise sea levels on the Atlantic coast of the United States, with potentially disastrous consequences.
Stefan Rahmstorf of the Potsdam Institute for Climate Impact Research, who co-authored the study published in Nature Geoscience on Thursday, told the Guardian that a weakened AMOC will increase the number and severity of storms hitting Britain and bring more waves. heat in Europe.
He said traffic had already slowed by about 15% and the impacts had been seen. “In 20-30 years it is likely to weaken even more, and this will inevitably affect our weather, so we would see an increase in storms and heat waves in Europe, and sea levels rise on the east coast of the US “, he said.
Graph
Rahmstorf and scientists at Maynooth University in Ireland and University College London in the UK have concluded that the current weakening has not been seen in the last 1,000 years after studying sediments, ice cores in Greenland and others. proxy data that revealed past weather patterns. time. AMOC has only been measured directly since 2004.
AMOC is one of the largest ocean circulation systems in the world, carrying surface hot water from the Gulf of Mexico to the North Atlantic, where it cools and becomes saltier until it sinks north of Iceland, which in turn extracts more warm water from the caribbean. This traffic is accompanied by winds that also help bring light and humid weather to Ireland, the UK and other parts of Western Europe.
Scientists have long predicted a weakening of AMOC as a result of global warming and have expressed concern that it could collapse altogether. The new study found that such a point will probably be decades away, but the continuation of high greenhouse gas emissions will bring it closer.
Rahmstorf said: “We risk triggering [a tipping point] in this century, and the circulation will rotate in the next century. It is extremely unlikely that we have already started it, but if we do not stop global warming, it is more and more likely that we will start it.
“The consequences of this are so great that even a 10% chance of triggering a malfunction would be an unacceptable risk.”
Research in 2018 has also shown a weakening of AMOC, but the work in Nature Geoscience says this has been unprecedented in the last millennium, a clear indication that human actions are to blame. Scientists have previously said that a weakening of the Gulf Stream could cause icy winters in Western Europe and unprecedented changes across the Atlantic.
AMOC is a large part of the Gulf Stream, often described as the “conveyor belt” that brings hot water from the equator. But the larger weather system would not completely fail if ocean circulation became unstable, as winds also play a key role. Circulation failed before, under different circumstances, for example at the end of the last ice age.
The Gulf Stream is separated from the jet stream that has contributed to extreme weather in the northern hemisphere in recent weeks, although, like the jet stream, it is affected by rising Arctic temperatures. Normally, the very cold temperatures in the Arctic create a polar vortex that maintains a constant stream of air currents, keeping that cold air in place. But higher Arctic temperatures have led to a weak, wandering jet stream, which has helped cold weather spread farther south, in some cases while bringing warmer weather to the north, in others contributing to extremes in the weather seen in the UK, Europe and the US in recent weeks.
Similarly, the course of the Gulf is affected by melting Arctic ice, which discharges large amounts of cold water into southern Greenland, disrupting the flow of AMOC. The impact of variations in the Gulf of Gulf is seen for much longer periods than variations in the current jet, but it will also bring more extreme weather as the climate warms.
In addition to causing more extreme weather in Europe and the east coast of the United States, weakening the AMOC could have serious consequences for Atlantic marine ecosystems, disrupting fish populations and other marine life.
Andrew Meijers, the deputy scientific leader of the polar oceans at the British Antarctic Survey, who was not involved in the study, said: “AMOC has a profound influence on the global climate, especially in North America and Europe, so this evidence of a weakening Continuous circulation is new critical evidence for the interpretation of future projections of the regional and global climate.
“AMOC is often modeled as having a tipping point below a certain circulating force, a point where relatively stable overturning circulation becomes unstable or even collapses. The continuous weakening of the upheaval means that we risk finding that point, which would have a profound and probably irreversible impact on the climate. ”
Karsten Haustein, of the German Center for Climate Services, also independent of the study, said the US could be at risk of stronger hurricanes as a result of the weakening Gulf Stream.
“While the AMOC will not collapse soon, the authors warn that the current could become unstable by the end of this century if heating continues uninterrupted,” he said. “The risk of stronger hurricanes on the east coast of the United States has already increased due to warmer ocean waters, as well as potential changes in traffic in Western Europe.”