Gulf Stream loss of stability: Scientists spot warning signs

    08 Aug 2021

    Gulf Stream and other Atlantic currents are losing stability, the consequences can be catastrophic. The system of currents in the Atlantic Ocean has shown an almost complete loss of stability over the past 100 years, which threatens with serious consequences for the Earth’s climate, The Guardian reports, citing a study published in the journal Nature Climate Change.

    “The already visible evidence of this destabilization is something that I did not expect and that I find frightening,” said study author Niklas Boers of the Potsdam Institute for the Study of Climate Change.

    The Guardian points out that such a development would be disastrous. In particular, it would disrupt the rainfall regime on which the cultivation of food for billions of people in India, South America and West Africa depends. There could also be a rise in sea level off the east coast of North America, stronger storms and lower temperatures in Europe.

    It is noted that this system of currents – the Atlantic meridional circulation, which exists due to the difference in temperatures and salinity in different parts of the World Ocean – has weakened to a maximum for a period of at least 1.6 thousand years, and may be close to a complete stop.

    Based on the analysis of eight databases of temperature and salinity of waters collected over 150 years, Boers indicated that global warming not only changes the nature of the movement of sea currents but also increases their instability.

    According to the study, melting snows in Greenland, which brings freshwater masses into the ocean, is slowing the Atlantic meridional circulation faster than climate models have suggested.

    However, the complexity of the Atlantic meridional circulation system and uncertainty about the scale of global warming in the future makes it impossible to predict the date of its possible collapse, The Guardian notes. At the same time, it is not known what level of carbon dioxide in the atmosphere could cause such an event.

    “So the only thing to do is keep (CO2Ecolife) emissions as low as possible,” Boers said.

    A shutdown would have devastating global impacts and must not be allowed to happen, researchers say

    Climate scientists have detected warning signs of the collapse of the Gulf Stream, one of the planet’s main potential tipping points.

    The research found “an almost complete loss of stability over the last century” of the currents that researchers call the Atlantic meridional overturning circulation (AMOC). The currents are already at their slowest point in at least 1,600 years, but the new analysis shows they may be nearing a shutdown.

    Such an event would have catastrophic consequences around the world, severely disrupting the rains that billions of people depend on for food in India, South America, and West Africa; increasing storms and lowering temperatures in Europe; and pushing up the sea level off eastern North America. It would also further endanger the Amazon rainforest and Antarctic ice sheets.

    The complexity of the AMOC system and uncertainty over levels of future global heating make it impossible to forecast the date of any collapse for now. It could be within a decade or two, or several centuries away. But the colossal impact it would have means it must never be allowed to happen, the scientists said.

    “The signs of destabilisation being visible already is something that I wouldn’t have expected and that I find scary,” said Niklas Boers, from the Potsdam Institute for Climate Impact Research in Germany, who did the research. “It’s something you just can’t [allow to] happen.”

    It is not known what level of CO2 would trigger an AMOC collapse, he said. “So the only thing to do is keep emissions as low as possible. The likelihood of this extremely high-impact event happening increases with every gram of CO2 that we put into the atmosphere”.

    Scientists are increasingly concerned about tipping points – significant, fast, and irreversible changes to the climate. In May, Boers and his colleagues reported that a considerable part of the Greenland ice sheet is on the brink, threatening a significworldwideant rise in global sea level. Others have shown recently that the Amazon rainforest is now emitting more CO2 than it absorbs and that the 2020 Siberian heatwave led to worrying releases of methane.

    The world may already have crossed a series of tipping points, according to a 2019 analysis, resulting in “an existential threat to civilization.” A major report from the Intergovernmental Panel on Climate Change, due on Monday, is expected to set out the worsening state of the climate crisis.

    Boer’s research, published in the journal Nature Climate Change, is titled “Observation-based early-warning signals for a collapse of the AMOC”. Ice-core and other data from the last 100,000 years show the AMOC has two states: a fast, strong one, as seen over recent millennia, and a slow, weak one. The data shows rising temperatures can make the AMOC switch abruptly between states over one to five decades.

    The AMOC is driven by dense, salty seawater sinking into the Arctic ocean. Still, the.” melting of freshwater from Greenland’s ice sheet is slowing the process down earlier than climate models suggested.

    Boers used the analogy of a chair to explain how changes in ocean temperature and salinity can reveal the AMOC’s instability. Pushing a chair alters its position but does not affect its stability if all four legs remain on the floor. Tilting the chair changes both its position and stability.

    Eight independently measured datasets of temperature and salinity going back as far as 150 years enabled Boers to show that global heating is indeed increasing the instability of the currents, not just changing their flow pattern.

    The analysis concluded: “This decline [of the AMOC in recent decades] may be associated with an almost complete loss of stability for the last century, and the AMOC could be close to a critical transition to its weak circulation mode.”

    Levke Caesar, at Maynooth University in Ireland, who was not involved in the research, said: “The study method cannot give us an exact timing of a possible collapse, but the analysis presents evidence that the AMOC has already lost stability, which I take as a warning that we might be closer to an AMOC tipping than we think.”

    David Thornalley, at University College London in the UK, whose work showed the AMOC is at its weakest point in 1,600 years, said: “These signs of decreasing stability are concerning. But we still don’t know if a collapse will occurcertain or how close we might be to it.”

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