Ocean currents regulating climate globally could collapse mid-century: Study

Collapse of ocean currents, that redistribute temperatures and precipitation between the tropics and the North Atlantic, is predicted to happen around mid-century if current greenhouse gas emissions persist, new research has found.

Shutting down these currents could have serious consequences for the Earth's climate, such as a colder future for Europe, increased warming in the tropics and increased storminess in the North Atlantic region, the research published in Nature Communications journal said.

The currents, called the Atlantic Meridional Overturning Circulation (AMOC), is estimated with high certainty to collapse in this century and most likely to occur in 2057, the analysis from the University of Copenhagen, Denmark, found using advanced statistical tools on ocean temperature data from the last 150 years.

"Our result underscores the importance of reducing global greenhouse gas emissions as soon as possible," said Peter Ditlevsen, co-corresponding author of the study.

The AMOC, part of the global system of ocean currents, significantly contributes towards spreading the heat from the tropics to the northernmost regions of the Atlantic by ensuring that at the northernmost latitudes, surface water is converted into deep, southbound ocean currents.

This creates space for northward moving equatorial surface waters, thus playing a critical role in maintaining the relatively mild climate of the North Atlantic region.

The researchers came to their conclusions after observing "early warning signals" exhibited by ocean currents as they become unstable. While such signals about the AMOC have been previously reported, advanced statistical methods have made an accurate prediction of the collapse of the currents possible.

The researchers analysed sea surface temperatures in a specific area of the North Atlantic from 1870 to present days. These sea surface temperatures are "fingerprints" testifying the strength of the AMOC, which has only been measured directly for the past 15 years.

"Using new and improved statistical tools, we've made calculations that provide a more robust estimate of when a collapse of the AMOC is most likely to occur, something we had not been able to do before," explained Susanne Ditlevsen, another co-corresponding author on the study.

The analysis contradicted the latest Intergovernmental Panel on Climate Change (IPCC) report's message, which considered an abrupt change in the AMOC very unlikely in this century.