Study: Collapse of Key Atlantic Ocean Current May Begin As Early As 2060

 

In the past few years, there has been a growing body of research looking into the potential weakening of the Atlantic meridional overturning circulation(AMOC). It is the Atlantic branch of the global ocean current system, responsible for transporting warm ocean water to the north, where it sinks and returns as cold, deep water to the South Atlantic. This circulation helps control the Northwestern European climate. In fact, AMOC is part of the reason Northern Hemisphere is on average 1.40C warmer than the Southern Hemisphere.

However, researchers have revealed rising risks for AMOC to reach a tipping point, especially as the global climate system changes. A key destabilizing factor for AMOC is changes in ocean salinity. Back in 1961, the U.S oceanographer Henry Stommel was among the first researchers to recognize how the Atlantic’s water salinity leads to AMOC tipping point. But as this research has progressed with time, there has been speculation about the role played by climate change.

Last week, researchers from Utrecht University in Netherlands released a groundbreaking study on the nexus between climate change and AMOC collapse. While the researchers published an almost similar study last year, the new paper uses data from the latest climate models contained under the Coupled Model Intercomparison Project Phase 6 (CMIP6). The recent IPCC report is based on data from CMIP6, which consists of climate models from various institutes around the world. Under CMIP6, some of the models have global warming projections beyond year 2100. This has provided a more granular approach in analyzing systems such as AMOC. Unfortunately, the findings are concerning.

Although previous studies indicated that AMOC collapse before 2100 was unlikely, the new paper shows that the tipping point could begin as early as 2060. “The risk of a tipping point by 2100 is over 90% under a high-emission scenario and over 50% under an intermediate climate change scenario,” said René van Westen, co-author of the study.

In this case, a tipping point is when deep convection in the northern Atlantic stops. One approach to the AMOC shut down is the ongoing loss of ice in the Arctic, which adds freshwater in the Atlantic, affecting the ocean salinity levels.

“The study provides rough estimates but main point is - this is a risk I used to consider less than 10%, and given the devastating impacts lasting many centuries we really want this to be less than 1%,” said Stefan Rahmstorf, Professor at Potsdam Institute for Climate Impact Research in Germany, who was also part of the study team.

A full shut down of AMOC would cause severe climate disruptions. Some studies have showed that if AMOC weakens, sea levels on the American northeast coastline would rise sharply. On the other side, cold air temperatures would expand to cover Iceland, Britain and Scandinavia, with unprecedented storms.