'We are approaching the tipping point': Marker for the collapse of key Atlantic current discovered

An image of an open oceans surface with crashing waves and a stormy sky.
The tipping point for the collapse of a key Atlantic Ocean current may have been discovered by scientists. (Image credit: HadelProductions/Getty Images)

Scientists have discovered a key warning sign before a crucial Atlantic current collapses and plunges the Northern Hemisphere into climate chaos. 

The Atlantic Meridional Overturning Circulation (AMOC) carries warm water north from the Southern Hemisphere, where it releases heat and freezes. The freezing process concentrates salt in the non-frozen portion of the ocean water; this extra-saline water sinks, travels back south and picks up heat again, restarting the conveyor belt. (The Gulf Stream is part of this belt.) 

This release of heat helps keep Europe, and to some extent North America, balmier than it otherwise would be. But sediment records over the past 100,000 years suggest that, at times, the AMOC has shut down abruptly, leading to major climate shifts over mere decades. 

Scientists believe we could be veering towards this scenario once again — potentially as early as 2025 — as a result of climate change. However, until now researchers had no way of telling if the current is on the path toward one of these tipping points.

In a new study, published today (Feb. 9) in the journal Science Advances, scientists found that the flow of fresh water into the Atlantic Ocean at a latitude of 34 degrees south (the latitude where South Africa sits) may indicate a key warning sign for an impending AMOC collapse. The team found that about 25 years before the AMOC collapses, this flow reaches a minimum).

Scientists don't have a long enough record of observations of freshwater flow at this spot to predict how far away the AMOC is from a tipping point right now. However, they do know that this flow has been declining.

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"We are approaching the tipping point, but we cannot deduce the distance to the tipping point," study first author René M. van Westen, a postdoctoral researcher in marine and atmospheric science at Utrecht University, told Live Science. 

Because the rising and sinking of the AMOC depends on the salinity of the water, this circulation is very sensitive to influxes of fresh water, van Westen said. As the climate warms and precipitation patterns change, the patterns of freshwater flow into the ocean change, too. 

The AMOC transports warm water from the Southern Hemisphere to the north, helping to keep Europe and other regions warm.  (Image credit: National Oceanic and Atmospheric Administration (NOAA).)

It's difficult to predict the outcomes, though, and finding the AMOC's tipping point requires simulating a gradual increase in freshwater flow in the northern Atlantic over more than 2,000 years, van Westen said. This is a long and computationally expensive process, but trying to cut corners by simulating large freshwater pulses is not as realistic or precise. 

The researchers modeled this gradual freshwater increase using state-of-the-art climate models. They found a long negative trend in freshwater flow at 34 degrees south — the southern border of the Atlantic Ocean — reaching a minimum about 25 years before the AMOC collapses. The minimum is not tied to a specific salinity value, but rather is relative to the patterns that came before, so researchers aren't sure how these conditions compare to today's. The AMOC collapse led to a complete lack of circulation and a loss of about 75% of the heat transport from south to north. 

If the AMOC were to collapse in the near future, the consequences would be dire. Without the AMOC, the Northern Hemisphere would get colder, and the southern hemisphere would get warmer, though by a lesser degree . The effects vary by region, but Europe would be hard hit, van Westen said, cooling between 9 and 18 degrees Fahrenheit (5 to 10 degrees Celsius) within a century. That's a huge swing, even compared with the current level of climate change, which is already having impacts. 

"On average, the global climate warms by about 0.2 degrees C [0.36 F] per decade," van Westen said. 

The collapse of the AMOC would also lead to changes in precipitation around the globe. For example, the wet and dry seasons in the Amazon rainforest would swap places, leading to major ecological impacts, the researchers wrote in the paper. 

"We know under climate change that this AMOC will gradually weaken and this [freshwater] parameter will become more negative, so it will destabilize the AMOC further," van Westen says. The message, he added, is that the need to halt climate change is urgent: "We need to stop emitting as a global society." 

Stephanie Pappas
Live Science Contributor

Stephanie Pappas is a contributing writer for Live Science, covering topics ranging from geoscience to archaeology to the human brain and behavior. She was previously a senior writer for Live Science but is now a freelancer based in Denver, Colorado, and regularly contributes to Scientific American and The Monitor, the monthly magazine of the American Psychological Association. Stephanie received a bachelor's degree in psychology from the University of South Carolina and a graduate certificate in science communication from the University of California, Santa Cruz. 

    So basically the 'experts' are saying , "We have no idea what the hell we are talking about."
  • Cyclonaut
    i'm sure the 'experts' will find a way to weave the narrative of CO 2 from fossil fuels being the root cause of this. Oh - and it's racist as well. .. I'm sorry - homophobic as well.
  • Ilium
    So, I suppose the evidence they found from the other times this occurred in prehistoric times were caused by humans using fossil fuels, right?
  • Robert Crabtree
    What is disconcerting is that clearly the tipping point is a precursor of a new ice age and no one mentions that. We know that historically over the last few million years the earth went through cycles where about 80% of the time was an ice age.
    The cycles appear to vary between 110-140,000 years.
    There was no man made influence in those cycles so independently of the present issues of global warming the earth will sooner or later enter a new ice age. This is far more serious than any warming. It will destroy the bread baskets of Asia, Russia, Europe and North America.

    What we really need to research more is if the current CO2 emissions are delaying an ice age, and whether one is imminent.
  • Icepilot
    admin said:
    A vital Atlantic current that includes the Gulf Stream and keeps our climate in check may be giving off a warning sign of collapse.

    We are approaching the tipping point:' Marker for the collapse of key Atlantic current discovered : Read more
    "we only have data since 2004, & the year to year variations are large. To pretend that such a short series is in any way significant is not only unscientific but fraudulent."
  • JR Ewing
    Let it collapse. We need a change.
  • Swan
    BBCLE said:
    So basically the 'experts' are saying , "We have no idea what the hell we are talking about."
    "But by all means, we must stop climate change!"