The importance of accurately measuring the Atlantic Meridional Circulation (AMOC)

The real climate risks to Ireland from changes to the Atlantic currents that sustain our mild climate are obscured by exaggerated claims in media headlines and movies.

That’s according to Dr Gerard McCarthy, a Maynooth University (MU) oceanographer at the Irish Climate Analysis and Research UnitS (ICARUS) in the Department of Geography, who has led a new article for Nature Climate Change.

AMOC: accurately measuring the Atlantic Meridional Circulation

The latest paper is a retrospective on a landmark 2015 study led by Professor Stefan Rahmstorf, which identified long-term Atlantic cooling as a sign that the Atlantic Meridional Circulation (AMOC) was weakening.

“The extreme climate collapse scenarios depicted in the Hollywood film, The Day After Tomorrow, and even in headlines of reputable mainstream media are often not grounded in scientific reality, but the genuine risks for Ireland are still significant and require proper planning,” said Dr McCarthy.

“It has happened that a new paper comes out, you get headlines saying the AMOC is going to collapse in the next few years. What we need to do is bring together a broader scientific voice to properly assess all the existing AMOC research literature, rather than having these seesawing headlines that concern and confuse our policymakers,” said Dr McCarthy.

Dr McCarthy added, “the study led by Stefan Rahmstorf, one of the most influential studies of AMOC, used changes in sea surface temperature records stretching back over a century to build its case. The records show that the stretch of ocean lying between Ireland and Canada is the only region on Earth that has systematically cooled while almost everywhere else warmed.

This retrospective paper, co-authored by Professor Hans-Otto Pörtner of the Alfred Wegener Institute in Bremerhaven,  considered the questions raised by the Rahmstorf paper and highlighted the need for a clearer scientific consensus, setting the stage for a larger international research project called the AMOC in Focus assessment report, which Dr McCarthy is co-leading and is sponsored by JPI Ocean and JPI Climate.

This project is a 60-scientist, 14-country initiative aimed at producing authoritative, usable guidance for policymakers in Europe and around the world.

Regarding what AMOC changes mean for Ireland’s future, Dr McCarthy said it’s likely we will see relative cooling in the Atlantic.

“Cooling is not really what I’m worried about. What concerns me is changes in precipitation patterns and storminess. A weakening AMOC tightens the temperature gradient that fuels Atlantic storms, like a taut elastic band – and then more of those storms get catapulted towards Ireland. Ireland sits right at the end of this system. We are hugely dependent on the heat it transports, so we need a clear consensus voice, grounded in science, to plan properly,” said Dr McCarthy.

Dr McCarthy is an expert on AMOC; the system of ocean currents, sometimes known as the Gulf Stream System, that is critical to Ireland’s temperate climate, despite it being at a similar latitude to southern Alaska.

He also co-chairs the ongoing AMOC in Focus assessment, which brings together leading scientists from across Europe, Canada, and the USA to assess the likelihood and risks of a potential disruption to the Atlantic Ocean’s circulation system and its associated implications for climate, ecosystems, people, and the economy.

The paper in Nature Climate Change will be available online tomorrow, once the embargo lifts.

About AMOC

The Atlantic Meridional Overturning Circulation (AMOC) is a system of ocean currents that moves warm water northwards in the Atlantic and returns colder water southwards at depth. It helps regulate climate—especially in Europe—by keeping temperatures milder and influencing rainfall and sea levels.

Scientists are closely monitoring the AMOC, as evidence suggests it may be slowing due to climate change. Changes to this system could have wide-ranging impacts on weather and ecosystems.

About ICARUS

The Irish Climate Analysis and Research Units (ICARUS), part of the Department of Geography at Maynooth University, is a national leader in climate change research, providing integrated climate system analysis, solutions, data, and advice to the scientific community, policymakers, and society at large, both nationally and internationally.

Under the leadership of Director Professor Peter Thorne, ICARUS conducts research that advances fundamental understanding of past, present, and future climate variability and change. The unit also delivers cutting-edge analysis of future impacts, vulnerabilities, and adaptation strategies in alignment with national and international strategic priorities.

ICARUS’ core research strands focus on atmospheric, terrestrial, and marine environmental change, palaeoclimatology, regional climate modelling, catchment hydrology, water management, and the assessment of environmental and socio-economic impacts and adaptation.

About Maynooth University

One of four constituent universities of the National University of Ireland, Maynooth University traces its origins to the foundation of the Royal College of St Patrick in 1795. It was formally established as an autonomous university in 1997. Maynooth University is one of Ireland’s fastest growing universities with more than 17,000 students, including over 2,500 postgraduates.

See more breaking stories here.