Atlantic currents impact climate

New research challenges a long-held understanding of how Atlantic currents affect global temperatures.

The North Atlantic Ocean’s circulation system, responsible for Ireland’s relatively mild climate, has weakened and is expected to weaken further in the coming decades with potentially disastrous consequences.

Strong ocean circulation has traditionally been associated with higher temperatures and sluggish circulation with cooler temperatures, but new research is challenging that view, asserting that weakened circulation could cause a surge in already rising global temperatures.

In an article published by widely-respected academic journal Nature, Dr Gerard McCarthy and Professor Peter Thorne, of Maynooth University’s Irish Climate Analysis and Research Units (ICARUS), analyse research by Professors Xianyao Chen of the Ocean University of China and Ka-Kit Tung of the University of Washington.

This research challenges the conventional understanding of how variations in a system of ocean currents called the Atlantic Meridional Overturning Circulation (AMOC) affects rates of global surface warming.

The AMOC is a system of currents stretching across the Atlantic Ocean that are generally characterised by a northward flow of warm water and a southward flow of colder, deeper waters.

On a global scale, the AMOC has been viewed as a vigorous force associated with elevated surface temperatures across the Atlantic Ocean, but this new research instead emphasises the role of the AMOC in taking heat from the surface and storing it in the deep ocean.

Global surface temperatures rose steadily from 1975 to 1998, but this growth slowed for 15 years — an event which gained popular attention as a ‘hiatus’. Since then, we have experienced the four warmest years on record; 2014-2017. Interest in this hiatus and what caused it has, therefore, waned considerably.

Dr McCarthy and Prof Thorne argue that the research may hold the key to explaining this hiatus and that understanding the mechanics behind it can help us prepare for future climate change.

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