Experts fear ‘sensitive’ ocean current could be a looming disaster

Doyle Rice

USA TODAY

Add more studies to the pile of research raising alarms about a looming climate disaster.

Scientists have been closely watching the Atlantic Meridional Overturning Circulation, known as AMOC, for years. In April, two studies noted that the critical current is in danger of weakening or even collapsing due to climate change. That could impact the climate conditions and weather for hundreds of millions of people.

“The Atlantic Meridional Overturning Circulation really is one of our planet’s key circulation systems,” said Niklas Boers from the Potsdam Institute for Climate Impact Research in Germany, the author of a previous study on the topic.

You might know the current from the movie “The Day After Tomorrow,” which took quite a few liberties in its depiction of what would happen if the current collapsed due to climate change.

The AMOC is a crucial conveyor belt for ocean water and air, which influence weather. Warm, salty water moves north from the tropics along the Gulf Stream off the U.S. East Coast to the North Atlantic, where it cools, sinks and heads south.

The faster the current moves, the more water is turned over from the warm surface to the cool depths. The cycle keeps northern Europe several degrees warmer than it would otherwise be and brings colder water to the eastern coast of North America. Now, a study released April 29 says the AMOC has changed rapidly in the past, due to “violent volcanic eruptions” that eventually cooled the entire planet.

Roughly 12,900 to 11,7 00 years ago, Earth rapidly cooled due to violent volcanic eruptions that disturbed the AMOC, the new study in the peer-reviewed journal Science Advances says.

Originally, scientists thought an extraterrestrial impact such as an asteroid or comet strike triggered the AMOC disruption, which scientists call the Younger Dryas period.

The new research, which examined North American sedimentary records, strengthens an alternative theory that attributes the cooling to a cluster of volcanic eruptions.

This isn’t the first study proposing that volcanoes affected the AMOC, “but this is one of the first to show a link in cluster of eruptions in ice cores and sediment records across North America at the timing of the Younger Dryas using geochemical evidence,” the lead author of the new study, Lucien Nana Yobo of Texas A&M, said in an email.

According to Nana Yobo, the eruptions cooled the Earth’s surface by blocking sunlight, which disrupted temperature and salinity in the North Atlantic Ocean – key drivers of the AMOC – leading to a slowdown. As a result, “temperatures dropped by several degrees in the Northern Hemisphere, likely altering ecosystems and forcing early humans to adapt to colder, shifting environments,” Nana Yobo said.

The current threat to the AMOC isn’t volcanoes, but excess carbon dioxide in the atmosphere from human- caused climate change.

Though the Younger Dryas period shift is a much more abrupt shift than what is currently happening, the research “shows how sensitive the AMOC is to climate disturbances,” Nana Yobo said.

“The Atlantic Meridional Overturning Circulation really is one of our planet’s key circulation systems.”

Niklas Boers

Potsdam Institute for Climate Impact Research