The Atlantic meridional overturning circulation (AMOC) is a major tipping element in the climate system, and a future collapse would severely impact the climate in the North Atlantic region. A forthcoming collapse of the AMOC is a major concern as it is one of the most important tipping elements in Earth’s climate system.
In a recent study, scientists from the University of Copenhagen‘s Niels Bohr Institute and Department of Mathematical Sciences forecast that if greenhouse gas emissions stay the same, the ocean current system that currently distributes cold and heat between the North Atlantic region and the tropics will cease entirely.
The Thermohaline Circulation, also known as the Atlantic Meridional Overturning Circulation (AMOC), will collapse, with 95% certainty, between 2025 and 2095, according to research using sophisticated statistical algorithms and data on ocean temperatures from the previous 150 years. This will probably happen in 34 years, in 2057, and might have significant negative effects, including tropical warming and an increase in storminess in the North Atlantic region.
Professor Peter Ditlevsen from the Niels Bohr Institute said, “Shutting down the AMOC can have serious consequences for Earth’s climate, for example, by changing how heat and precipitation are distributed globally.”
“While a cooling of Europe may seem less severe as the globe as a whole becomes warmer, and heat waves occur more frequently, this shutdown will contribute to an increased warming of the tropics, where rising temperatures have already given rise to challenging living conditions.”
“Our result underscores the importance of reducing global greenhouse gas emissions as soon as possible.”
The prediction made by the researchers is supported by observations of early warning signs that ocean currents display when they become unstable. These Thermohaline Circulation Early Warning Signals have been observed in the past. Still, it has only recently been able to estimate when a collapse will occur, thanks to the development of sophisticated statistical techniques.
In a specific region of the North Atlantic, sea surface temperatures were examined from 1870 to the present. These sea surface temperatures, which have only been directly recorded for the past 15 years, are “fingerprints” attesting to the power of the AMOC.
Professor Susanne Ditlevsen of UCPH’s Department of Mathematical Sciences said, “Using new and improved statistical tools, we’ve made calculations that provide a more robust estimate of when a collapse of the Thermohaline Circulation is most likely to occur, something we had not been able to do before.”
Since the previous ice age, when the circulation collapsed, the thermohaline circulation has operated in its current configuration. It has been noted that abrupt climate shifts between the AMOC’s current state and its collapsed condition have occurred 25 times in association with the ice age climate. These renowned Dansgaard-Oeschger episodes were the ones that were initially identified in ice cores from the Greenlandic ice sheet. While climate change today is 1.5 degrees warming over a century, it was dramatic during previous episodes, changing by 10-15 degrees over a decade.
Journal Reference:
- Ditlevsen, P., Ditlevsen, S. Warning of a forthcoming collapse of the Atlantic meridional overturning circulation. Nat Commun 14, 4254 (2023). DOI: 10.1038/s41467-023-39810-w