Atlantic meridional overturning circulation (AMOC) is a large-scale ocean current and a major part of the global thermohaline circulation, which distributes heat around the planet and significantly contributes to the structure of atmospheric air circulation. The stability of the AMOC is a big part of why, for instance, TERF Island–which has roughly the same latitude as Newfoundland–is temperate instead of being a frozen hellscape. For a couple of decades, climate scientists have been warning that the combination of temperature increase and fresh water influx from melting ice might destabilize this current, eventually leading to a catastrophic “phase change” in which the circulation goes from relatively stable to completely absent in a very short (i.e. on the scale of decades) amount of time.

The first detailed study and simulation of contemporary AMOC dynamics suggests that we are much closer to this tipping point that we previously thought, and that the process of collapse might have already begun. It is impossible to overstate how bad this would be. The AMOC drives temperature, precipitation patterns, and a whole host of other aspects of the global climate–its stability is one of the major reasons for the Holocene climate optimum that we have enjoyed for all of our species’ history. A collapse would be incredibly bad for us and for the biodiversity of the planet as a whole.