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The Gulf Stream, which regulates the climate of the Outer Hebrides, is dangerously close to switching off, new scientific research suggests.

The findings, which support previous studies about the imminent collapse of the Gulf Stream, mean the Isles are in line for much harsher and colder weather than at present.

The Atlantic Meridional Overturning Circulation (AMOC), part of which is the Gulf Stream, is an ocean current system that transfers warm salty water northward.

For millennia, the Gulf Stream has transported warm Gulf of Mexico water across the Atlantic to Europe. As a result of global warming, the Greenland ice sheet is releasing massive quantities of freshwater into the North Atlantic, cooling the AMOC - which transfers the bulk of Gulf Stream heat - and propelling it towards a "tipping point".

If this ocean current collapses, temperatures in Europe will plunge, according to the latest climate modelling; London would cool by an average of about 8C and Bergen, Norway, by 15°C.

"The temperature, sea level and precipitation changes will severely affect society, and the climate shifts are unstoppable on human time scales," the authors of the latest Utrecht University study, published in Science Advances, warn.

The AMOC has been slowing down significantly since the mid-1900s.

With increasing contributions of freshwater from melting glaciers and greater rain, concentrations of salt in the seawater drop, and the saline water becomes less dense, disrupting the sinking process and weakening the entire physical cycle.

By modelling these ocean systems, René van Westen and his Utrecht University colleagues have found a way to detect when the AMOC' tipping point' is near: the decline in salinity will slow down at the southernmost boundary of the Atlantic.

"Once a threshold is reached, the tipping point is likely to follow in one to four decades," say the authors.

The new modelling explores the freshwater-induced tipping point itself rather than trying to predict its timing.

However, the resulting data suggests AMOC is much more sensitive to changes than most climate models have accounted for.

AMOC impacts much of Earth's climate, so it is one of the tipping elements in Earth's climate system that researchers are most concerned about. The collapse of the AMOC happens cyclically over a million-year scale. Based on past occurrences, we know the Arctic should extend south during this time, leading to decreased temperatures in northwestern Europe by up to 15 °C, disrupting tropical monsoons and heating the Southern Hemisphere even further.

The following chain of reactions will severely impact entire ecosystems and global food security.

Image credit: National Oceanic and Atmospheric Administration (NOAA)