7. Major Atlantic Ocean current system may be approaching critical threshold

A study published in the journal Nature Climate Change suggested that the Atlantic Meridional Overturning Circulation (AMOC) may have been losing stability in the course of the last century.

The AMOC transports warm water from the tropics northward at the ocean surface and cold water southward at the ocean floor, which is particularly relevant for the relatively mild temperatures in Europe. Furthermore, its influence on weather systems worldwide means that a potential collapse of the ocean current system could have severe consequences.

The study was conducted as part of the European TiPES project, coordinated by the University of Copenhagen, Denmark, and the Potsdam Institute for Climate Impact Research (PIK), Germany.

According to a news release by PIK, it has previously been shown that the AMOC is currently at its weakest in more than 1,000 years. However, so far it remains an open question as to whether the observed weakening corresponds to a change in the mean circulation state, or whether it is associated with an actual loss of dynamical stability.

"The difference is crucial," said the study's author Niklas Boers, "because the loss of dynamical stability would imply that the AMOC has approached its critical threshold, beyond which a substantial and in practice likely irreversible transition to the weak mode could occur."