Early Ocean Current Warning Signs May Herald Abrupt Climate Change

It turns out that abrupt climate change may be possible. Scientists have found early warning signals of a reorganization of the Atlantic ocean's circulation, which could have a profound impact on the global climate system.

In order to better understand current climate change, the researchers used a simulation from a highly complex model in order to analyze the Atlantic Meridional Overturning Circulation (AMOC), which is an important component of the Earth's climate system.

The AMOC is a bit like a conveyor belt in the ocean. It's driven by the salinity and temperature of the water. More specifically, the system transports heat energy from the tropics and Southern Hemisphere to the North Atlantic, where it's transferred to the atmosphere.

In theory, if the AMOC is "switched off" due to extra freshwater entering the North Atlantic, surface air temperature in the North Atlantic region could cool by one to three degrees Celsius. In fact, enhanced cooling of up to eight degrees could occur in the worst affected regions. This, in turn, would encourage drought in the Sahel, which is the region just south of the Sahara desert, and would also affect sea level along the coasts of Europe and North America.

"We found that natural fluctuations in the circulation were getting longer-lived as the collapse was approached, a phenomenon known as critical slowing down," said Chris Boulton, lead author of the new study, in a news release.

Currently, the researchers aren't sure how close to a collapse the circulation might be. However, an early warning to potentially help scientists prevent it or prepare for its consequences.

"The best early warning signals in the model world are in places where major efforts are going into monitoring the circulation in the real world-so these efforts could have unexpected added value," said Tim Lenton, one of the researchers.

The findings are published in the journal Nature Communications.

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