Unlike many parts of the world enduring rising temperatures due to climate change, Ireland is likely to experience cooling arising from sustained weakening of the Gulf Stream that normally gives the country its temperate climate, according to a new report.
However, the Irish Ocean Climate and Ecosystem Status Report 2023, published on Thursday by the Marine Institute, confirms that Ireland will not escape other consequences of a warming planet.
Among the key findings are sea level rises of between 2-3mm per annum since the 1990s; a rise of about 0.5 degrees in sea surface temperatures on Ireland’s north coast over the past 10 years; increased acidification of surface waters and year-round presence of harmful algal species – probably due mostly to increased temperatures caused by human-induced climate change.
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Ireland is likely to see larger cold blooded fish species move north towards polar regions, while smaller Mediterranean species such as the anchovy will be found increasingly in our waters, it finds.
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The Gulf Stream, a strong ocean current that brings warm water from the Gulf of Mexico into the Atlantic Ocean, is predicted to decrease by 30 per cent into the future, with a low risk it will collapse completely, said report co-author Dr Gerard McCarthy of the ICARUS research facility at Maynooth University.
Also known as the Atlantic Meridional Overturning Circulation (Amoc), he said it disappeared before, in the last ice age – some 14,000 years ago – which saw glaciers return to Ireland. There is already evidence of its weakening, with Irish surface waters cooling in recent years after peaking in 2007. “Understanding how this is changing is a key research priority,” said Dr McCarthy, who underlined that “we have unique climate risks often tangled up with the Atlantic”.
He agreed that a weakening of the Gulf Stream system and its cooling effect is “a bit surprising when the whole world is warming”, and said this fact gets lost in the climate conversation in Ireland. Policy should not be determined by global average temperatures.
Separate to rising global sea levels, Dr McCarthy said a hangover from the ice age meant the southern part of the island was sinking, which was accelerating sea level rise beyond what was being seen in the north.
If the melting of the Greenland ice sheet was dominant in future decades, he said, sea levels would decrease in Ireland overall because of “a see-saw effect”. Should Antarctic ice melting come to the fore the country is predicted to experience a rise of 15 per cent more than the global average.
The mean sea level for the Irish coast is projected to increase by between 25cm and 80cm this century depending on the greenhouse gas emissions trajectory considered.
In spite of a weakened Gulf Stream Ireland faces a stormier future with more rainfall in winter and less in summer. With a preponderance of surface waters over land, this means conditions could change quickly to a hosepipe ban despite being preceded by a long period of heavy rainfall, the report notes.
Speaking as the report was published, Minister for the Marine Charlie McConalogue underlined the importance of research providing high-quality evidence for scientists and policymakers on “the changing state of our seas”.
With Ireland’s climate dominated by the influence of the Atlantic Ocean, Mr McConalogue said “tackling emissions will help Ireland address rising sea levels, ocean warming and acidification, along with coastal inundation”.
“We also need to predict or project what will happen to our oceans in the future using climate models. Based on this evidence we have set out ambitious climate action targets that include an annual reduction in emissions,” he added.
Marine Institute chief executive Paul Connolly said changes in the ocean affect seafood, transport and biodiversity, and that land-based activities can have negative impacts on marine life.
“The oceans provide 50 per cent of the oxygen we breathe. They are a critical element of the global climate system in their role to regulate atmospheric processes and for distributing heat, salt and organisms. This research shows the impact of climate change is already evident in Irish marine waters with patterns of harmful algal blooms changing. The ocean off the southwest coast will likely become warmer and less salty by the year 2035.”
The report is a collaboration between marine researchers in the Marine Institute and climate scientists from Met Éireann; Maynooth University, University of Galway, Atlantic Technological University, National Parks & Wildlife Service, Birdwatch Ireland, Trinity College Dublin, University College Dublin, Inland Fisheries Ireland, the National Water Forum, the EPA and Dundalk Institute of Technology.
