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Scientists warn Gulf Stream under threat, with ‘increased storminess’ for Ireland and north Atlantic region


The Atlantic Meridional Overturning Circulation (AMOC), or gulf stream, is part of a global system of ocean currents. It accounts for the most significant part of heat redistribution from the tropics to the most northerly regions of the Atlantic – especially to western Europe.

The gulf stream plays a vital role in Ireland’s climate by ensuring much milder winters than other countries at the same latitude.

In a new study, researchers from the University of Copenhagen’s Niels Bohr Institute and Department of Mathematical Sciences predict that the system of ocean currents will completely stop if mankind continues to emit greenhouse gases at the current rate.

Using advanced statistical tools and ocean temperature data from the last 150 years, the researchers calculated that the ocean current, also known as the Thermohaline Circulation, will collapse, “with 95pc certainty”, between 2025 and 2095. They found that the collapse will most likely occur in 2057 and said it could result in major challenges – such as warming in the tropics and “increased storminess” in the north Atlantic region.

At the northernmost latitudes, circulation ensures that surface water is converted into deep, southbound ocean currents. The transformation creates space for additional surface water to be moved northward from equatorial regions. This Thermohaline Circulation is critical for maintaining the relatively mild climate of the north Atlantic.

Lead researcher Professor Peter Ditlevsen, from the Niels Bohr Institute, said: “Shutting down the AMOC can have very 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 heatwaves 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 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 Thermohaline Circulation is most likely to occur, something we had not been able to do before,” said Professor Susanne Ditlevsen of UCPH’s Department of Mathematical Sciences.

The Thermohaline Circulation has operated in its present mode since the last ice age, where the circulation was indeed collapsed. Abrupt climate jumps between the present state of the AMOC and the collapsed state has been observed to happen 25 times in connection with ice age climate. These are the famed Dansgaard-Oeschger events first observed in ice cores from the Greenlandic ice sheet. At those events climate changes were extreme with 10-15C changes over a decade, while present days climate change is 1.5C degrees warming over a century.

The findings contradict the message of the latest Intergovernmental Panel on Climate Change (IPCC) report, which based on climate model simulations said an abrupt change in the Thermohaline Circulation is very unlikely during this century.

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