Nature Climate Change, August 5
The Atlantic Ocean’s major circulation system could be approaching a critical threshold. It is exhibiting two early-warning signs of collapse: rising surface temperatures, and decreasing salinity. Higher air and ocean temperatures have accelerated glacier melt and ice loss around the world, particularly in the Arctic. Rapid melt of Arctic glaciers and the Greenland ice sheet has increased the flow of freshwater into the North Atlantic. This sudden influx of buoyant freshwater slows the Atlantic’s greatest circulation system, the AMOC (“Atlantic Meridional Overturning Circulation”) by preventing it from pushing denser, saltier water to the bottom of the ocean. Over the past two decades, both these warning signs have been observed, signaling that this major circulation system may be losing strength, and approaching an irreversible threshold that jeopardizes its stability. Although the scientific community has welcomed these results with caution, the collapse of current Atlantic circulation would severely impact not just the North Atlantic, but global climate patterns; threatening the Antarctic ice sheet, tropical monsoon systems, Amazon rainforest, and coastal regions across the world.