Media release
From: Springer NatureAtlantic Ocean current could collapse by mid-century
The Atlantic Meridional Overturning Circulation (AMOC) — a large system of ocean currents that carry warm water from the tropics northwards into the North Atlantic — could collapse around the middle of the century, or potentially any time from 2025 onwards, under continued greenhouse gas emissions. These estimates, reported in Nature Communications, highlight the impact of human activities on the Earth’s climate system.
The AMOC is one of the most important tipping elements, a subsystem capable of switching into an irreversible state, in Earth’s climate system. Its potential collapse is a major concern and would have severe impacts on the climate of the North Atlantic region and around the world. This kind of abrupt climate change was last experienced during Dansgaard-Oeschger events in the last glacial period caused by the collapse and restoration of the AMOC. This led to mean Northern hemisphere temperature fluctuations of 10–15 degrees celsius within a decade, much greater than present changes of 1.5 degrees in a century. The strength of the AMOC has only been monitored continuously since 2004 and these observations have shown AMOC to be weakening, but longer records are needed to assess the magnitude. The recent IPCC assessments suggest that a full collapse of the AMOC is unlikely within the 21st century.
Peter Ditlevsen and Susanne Ditlevsen analyzed sea surface temperatures in the North Atlantic between 1870–2020 as a proxy for AMOC. These records date back much further than direct AMOC measurements and can give more robust information on temperature trends. The authors found early warning signals of a critical transition of the AMOC system and suggest that it could shut down or collapse as early as 2025 and no later than 2095.
The authors do not make assumptions regarding the drivers of the AMOC change but point out that atmospheric CO2 concentrations have increased almost linearly within the time period studied. However, other mechanisms at play cannot be excluded, and it cannot be ruled out that the collapse could be partial.
