'Giant Ocean Conveyor Belt' May Fall Sooner Than Thought

Last year, climate scientists sent up a red flag over the potential collapse of the Atlantic Meridional Overturning Circulation, or AMOC, a network of ocean currents in peril from climate change. That warning indicated it could be decades before that happens, but a new analysis suggests such a "devastating" collapse could be more imminent—and dozens of researchers are now begging Nordic policymakers to take action, reports the Guardian. "A string of scientific studies in the past few years suggests that this risk has so far been greatly underestimated," the 44 experts from 15 nations write in an open letter to the Nordic Council of Ministers published Monday. The letter adds: "Such an ocean circulation change would have devastating and irreversible impacts especially for Nordic countries, but also for other parts of the world."

AMOC—which Live Science describes as "a giant ocean conveyor belt that includes the Gulf Stream and transports vital heat to the Northern Hemisphere"—brings warm water from the tropics north and sets it loose in the subpolar Atlantic. Once that water cools, it sinks and then returns south, per the Guardian. That important heat transfer "determines life conditions for all people in the Arctic region and beyond and is increasingly at risk of passing a tipping point," the scientists note in their letter. An AMOC breakdown could hurl the planet's climate "into chaos," per the Guardian, affecting everything from sea levels, ocean oxygen levels, and rainfall patterns, which in turn would disrupt marine ecosystems, agriculture, and, ultimately, food supplies.

When that "tipping point" may come is still unclear, but one thing the scientists worry about is that the Intergovernmental Panel on Climate Change's 2023 prediction, with "medium confidence," that the AMOC "will not collapse abruptly before 2100." That risk is being seriously underestimated by the IPCC, they say, adding that they want policymakers in the Nordic nations—including Sweden, Norway, Finland, Denmark, and Iceland—to keep the pressure on internationally to hew as closely as possible to the targets of the 2015 Paris climate agreement. "The passing of this tipping point is a serious possibility already in the next few decades," the scientists write. Their letter in full here. (More ocean currents stories.)