Covering or not stopping and if so: when? That is the big question that keeps scientists investigating the greatest sea currents in the Atlantic Ocean. According to new research by Dutch climate scientists from Utrecht University That Sunday appearedwould this amoc (Atlantic Meridional Overturning Circulation) Being able to reach a tipping point this century. That is no surprise for Oceanographers: “The collapse has since become a very real possibility,” said Oceanograil Sybren Drijfhout, who was not involved in the investigation.
The Amoc is a large system of ocean currents in the Atlantic Ocean and an important part of the global ocean circulation. The warm gulf stream for the North American coast is the most famous part of it. This brings the amoc warm tropical sea water to Western Europe, making the climate here relatively mild. Once in the Arctic area, the seawater cools down, the density increases and sinks. This cold current flows back to the south at a depth of kilometers.
Climate change influences the amoc: among other things, extra (sweet) melt water from the Greenland ice sheet makes the water in the north less salt and therefore less heavy. As a result, it sinks less quickly and slows the flow. A strongly delayed or even as good as stagnant amoc can cause considerable shifts of the global climate: from strongly falling or rising temperatures to changing precipitation patterns, more storms and more sea level rise. The northern hemisphere and in particular Western Europe will cool down, the southern hemisphere warms up extra.
Substantially weaker
The Utrecht researchers used 25 climate models in their analysis and conclude that the amoc can reach the tipping point in a moderate emission scenario in the second half of this century and can collapse. That does not mean that the amoc stops from one day to the next: it probably takes about a hundred years before the flow is actually substantially weaker. In the scenario with low emissions and therefore less warming, the chance of a collapse of the Amoc is smaller.
Sjoerd Groeskamp, physical oceanographer at the NIOZ (Royal Netherlands Institute for Research Der Zee) and not involved in the research, says that the results are in line with other studies in the past three years. “They consistently point out that we are approaching a tipping point, whether it is in 2060 or 2100. The tipping point is closer than we thought and we can also achieve it with a smaller rise in temperature.”
At the end of February, however, other research showed that the Amoc would not stop this century. These types of studies into very complex system are done with imperfect models, Groeskamp responds. That is why the results are always slightly different. He says that Utrecht research has probably not taken the effect of mixing in the oceans enough. “In general, everything mixes everything, so I can imagine that if you take it with you, the tipping point moves slightly backwards in time. We can talk about such details, but totally independent research groups show the same trend, that is really disturbing.”
Disinterest
Sybren Drijfhout, Oceanographer at the KNMI, also finds the results not surprising. Driftwood is responsible for the chapter on the amoc in the IPCC report on the Amoc. The IPCC, the United Nations Climate Office, concluded in its latest report from 2021 that the Amoc this century ‘Very Likely’ Furthermore, will delay. And there was ‘Medium Confidence’ that the tipping point is not reached for 2100. According to the latest insights, that would now ‘As likely as not’ Must be, says driftwood. In other words: a 50% chance that the amoc will reach the tipping point before the end of the century. “You can’t even exclude that we are already over the tipping point,” he adds.
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What makes research into the amoc difficult is the lack of measurements over a long period. The ocean flow has only been measured for the last twenty years, and only the last ten years really in the right place in the North, according to Groeskamp. Too short to be able to unravel the natural variability of the current. “We have to measure longer and more in the sea to gain a better insight into the actual situation and to be able to adjust models better.”