New research published in Nature Climate Change found that planetary warming has placed a critical Atlantic current, called the Atlantic Meridional Overturning Circulation (AMOC), at risk of collapse. The AMOC is a water pattern within the larger Gulf Stream that circulates warmer water from the southern Atlantic into cooler northern regions. On a local level, it regulates temperatures for much of Europe and transports nutrients that support northern fisheries. If the AMOC collapses, scientists say, effects will be felt around the world.

The AMOC is at its weakest point in 14,500 years -- since the end of the last ice age when glaciers began melting and freshwater diluted the salinity of the ocean, slowing the current. Once the AMOC fully collapsed, temperatures dropped across the entire Northern hemisphere for the next 3,000 years. Scientists predict a present-day collapse would equate to a permanent La Niña state, where significant changes to wind, temperatures, and precipitation patterns would cause substantial and unpredictable increases in extreme weather conditions, such as drought, monsoons, and hurricanes.

Why This Matters

The collapse of a major ocean current is yet another example of how the climate crisis is chipping away at the world’s natural systems. Due to due to planetary warming, the AMOC is at a “major climate tipping point,” with its flow declining by 15% since 1950. At the same time, the world’s glaciers are again melting, and many face the imminent risk of collapse. Longer-lasting La Niña seasons are also exacerbating extreme weather conditions, including the record-breaking drought in the Western US and flood season in China. Meanwhile, primarily human-caused carbon emissions are at a three million-year high, adding to the warming effect and its related impacts.

A Question Of Magnitude

Because of the complexity of the AMOC, uncertainty remains around the potential outcomes. As study author, Byram Orihuela-Pinto put it in an email to Gizmodo: “This is not a projection study, but a what-if scenario. The AMOC is slowing down, it is projected to slow further, and our work [only] looks at what this might mean for global climate if the current collapses altogether.”

Regardless, instability will be felt -- it’s more a question of magnitude and how to manage those effects. In August, Peter de Menocal, President of the Woods Hole Oceanographic Institution, commented on another AMOC study, likening the current to an emergency room patient. “All the signs are consistent with the patient having a real mortal problem,” he stated to the Washington Post.