Instability in Atlantic ocean currents may impact global climate: Study

A recent study published by Germany’s Potsdam Institute for Climate Action Research (PIK) in the journal ‘Nature Climate Change‘ reveals that the Atlantic ocean current system might be losing stability. The system of currents helps control temperatures in the Northern Hemisphere and the potential collapse could have severe consequences for climate systems worldwide, scientists say. 

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The Atlantic Meridional Overturning Circulation (AMOC)  transports warm water masses from the tropics northward at the ocean surface and cold water southward at the ocean bottom, which is most relevant for the relatively mild temperatures in Europe. The Gulf stream, which is a part of AMOC, helps maintain the energy balance in the Atlantic Ocean. The instability is caused by human actions, the study states. 

“The Atlantic Meridional Overturning really is one of our planet’s key circulation systems. We already know from some computer simulations and from data from Earth’s past, so-called paleoclimate proxy records, that the AMOC can exhibit — in addition to the currently attained strong mode — an alternative, substantially weaker mode of operation. This bi-stability implies that abrupt transitions between the two circulation modes are in principle possible,” Niklas Boers, the author of the study, from the Potsdam Institute for Climate Impact Research, Freie Universitat Berlin and Exeter University said as per CNN reports. 

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The study comes days ahead of a major report by the UN’s International Panel on Climate Change on Monday. 

The AMOC is currently at its weakest in more than 1000 years, the study says. However, the weakening could also correspond to a change in the mean circulation state. Its connection to actual loss of dynamical stability is not established. 

“The difference is crucial 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, “Boers added.

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“Imagine a chair, which can be either shifted (with all four legs remaining on the ground) or tilted. Both change the position of the chair (corresponding to the change in mean AMOC strength), but in the first case the stability of the chair won’t be affected, while in the latter case there exists a critical point. If we tilt the chair just slightly further, it will fall down. My results suggest that what is happening to the AMOC is more likely to be a tilting than only a shifting, so the AMOC has moved toward the critical threshold at which it may collapse,” he said.

“Every gram of extra greenhouse gas in the atmosphere will increase to the probability of an AMOC collapse in the future, so emitting as little as possible, both on individual but of course also on collective and international level, is the key.”