Sediments and ice cores show that the warm ocean current that maintains northern Europe habitable is weaker than it has ever been in the last thousand years. The discovery raises the possibility that the current will weaken even more, which would be disastrous for the UK and Ireland and bad news for many other locations.
Northern Europe’s climate has been governed for thousands of years by the Gulf Stream System, also known as the Atlantic Meridional Overturning Circulation (AMOC). Prior to that, the Younger Dryas event, which briefly returned the Earth to the ice age it had recently emerged from, is thought to have been caused by the AMOC’s near-total shutdown 12,000 years ago.
Oceanographers have argued over whether a recent weakening is a random decline or the beginning of a terrifying trend by comparing it to previous movements. Multiple lines of evidence have been compiled by Professor Stefan Rahmstorf of the Potsdam Institute for Climate Impact Research to show the AMOC’s resilience since 400 AD.
“The Gulf Stream System functions like a massive conveyor belt, delivering cold, low-salinity deep water back down south and transporting warm surface water from the equator up north. It flows water at a rate of over 20 million cubic meters per second, or one hundred times the Amazon flow “said Rahmstorf in a release.
The system has diminished by 15% since the middle of the 20th century, according to recent direct measures of its strength. However, proxy information from ice cores, corals, tree rings, and ocean sediments can show how strong it was in the past.
There are enough differences or missing periods in each individual proxy to raise a lot of doubt. The Gulf Stream has not been this feeble for at least 1,600 years, said Rahmstorf and co-authors in Nature Geoscience, after putting all the pieces together.
The North Atlantic’s sinking of dense, salty water is what propels the AMOC. Freshwater that is lighter messes with the procedure. It is feared that excessive rains or ice melting from nearby locations will be sufficient to impede and interrupt the entire process.
The disaster movie The Day After Tomorrow was inspired by the fact that if the AMOC stops, Europe will freeze, a process that is speeded up 1,000-fold. Meanwhile, the accumulation of water being pushed north will speed Florida’s drowning by accelerating sea level rise along the American east coast.
Rahmstorf’s findings were released the same week as modeling data that suggested the volume and velocity of freshwater entering the North Atlantic might have an equal impact on the AMOC. If true, this would significantly raise the risk we face because a little period of heat-induced melting of Greenland’s ice, such that observed in 2019, could be enough to function as a very unfavorable trigger.