In recent years, scientists have warned about a weakening of the Atlantic Meridional Overturning Circulation (AMOC), which transports warm, salty water from the tropics to northern Europe and then sends colder water back south along the ocean floor. Researchers who study ancient climate change have also uncovered evidence that the AMOC can turn off abruptly, causing wild temperature swings and other dramatic shifts in global weather systems.Happy Thursday everybody.
Scientists haven't directly observed the AMOC slowing down. (emphasis mine) But the new analysis, published Thursday in the journal Nature Climate Change, draws on more than a century of ocean temperature and salinity data to show significant changes in eight indirect measures of the circulation's strength.
If the circulation shuts down, it could bring extreme cold to Europe and parts of North America, raise sea levels along the U.S. East Coast and disrupt seasonal monsoons that provide water to much of the world.
"This is an increase in understanding ... of how close to a tipping point the AMOC might already be," said Levke Caesar, a climate physicist at Maynooth University who was not involved in the study.
In its 2019 "Special Report on the Ocean and Cryosphere in a Changing Climate," the U.N. Intergovernmental Panel on Climate Change projected that the AMOC would weaken during this century, but total collapse within the next 300 years was only likely under the worst-case warming scenarios.
The new analysis suggests "the critical threshold is most likely much closer than we would have expected," Boers said.
The "restoring forces," or feedback loops, that keep the AMOC churning are in decline, he said. All the indicators analyzed in his study - including sea surface temperature and salt concentrations - have become increasingly variable.