The water in the Atlantic Ocean is constantly circulating in a complex pattern that affects the weather on different continents. And climate scientists have asked a crucial question: whether this massive system, including the Gulf Stream, is slowing because of climate change.
If it were to change significantly, the consequences could be dire, including potentially faster sea level rise along parts of the eastern United States and Europe, stronger hurricanes storming into the southeastern United States, less rainfall in parts of Africa, and changes in the tropical monsoon systems.
Now, scientists have discovered the early warning signs that this critical ocean system is at risk, according to a new analysis published Thursday in the scientific journal Nature Climate Change.
“I showed that this gradual slowing of the circulatory system is accompanied by a loss of stability,” said Niklas Boers, a researcher at the Potsdam Institute for Climate Impact Research in Germany, “and approaching a tipping point where it would abruptly transition to a much slower state.”
Alex Hall, the director of the Center for Climate Science at the University of California, Los Angeles, who was not involved in the study, said that while the findings didn’t signal him that a collapse of that ocean system was imminent, the analysis offered. a crucial reminder of the risks of interference with currents.
“We’re poking a beast,” he said. “But we don’t really know what reaction we will cause.”
Studying ocean systems is difficult for many reasons. One challenge is that there is only one Earth, says Andrew Pershing, director of climate science at Climate Central, an organization of scientists and journalists that focuses on climate change. Consequently, researchers can’t easily compare two oceans — one that has to do with the effects of global warming caused by increased carbon dioxide in the atmosphere, and another that hasn’t dealt with that problem.
dr. Pershing praised the analytical solutions the scientists devised to study the ocean-spanning tangle of currents known as Atlantic Meridional Overturning Circulation, or AMOC. By analyzing more than a century of ocean temperature and salinity data, Dr. Boers observed significant changes in multiple indirect measures of AMOC strength.
“The work is fascinating,” he says.
dr. Pershing said analysis supported the idea that the AMOC has weakened over the 20th century. It’s a critical area to study because AMOC embodies the idea of climatic “tipping points” — hard-to-predict thresholds in Earth’s climate system that, once crossed, have rapid, cascading effects far beyond the corners of the globe where they occur. occur.
“The big challenge is: what do we do with that information?” he said of the new study.
Susan Lozier, a physical oceanographer and dean at Georgia Tech’s College of Sciences, said there is no doubt that climate change is affecting the oceans. There is broad consensus in her field that sea levels are rising and the oceans are warming, she said.
She also called Dr. Boers’ study “interesting,” but said she wasn’t convinced the findings showed that circulation in that ocean system is slowing. “There are many things to worry about with the ocean,” she said, such as the more definitive concerns about sea level rise.