A new scientific study suggests that the combination of increasing water temperatures and melting glaciers poses a significant threat to a major ocean current.
The study, published Tuesday in the journal Nature, found that the Atlantic Meridional Overturning Current, which includes the Gulf Stream and which plays a crucial role in regulating global climates and air temperatures, could collapse as early as 2025.
"What's special about the shot-off or the change of this ocean current is that it could be irreversible," said Peter Ditlevsen, one of the co-authors of the alarming report.
The AMOC behaves as a sort of global conveyor belt. It is a continuous process in the Atlantic Ocean that moves water back and forth from north to south, in a circulation pattern that distributes warmth to different regions around the world and transports essential nutrients to support marine life in the ocean.
The study explains that with rising global temperatures, the current is now seeing an influx of fresh water from melting glaciers, resulting in a reduction of its salinity. This change, in turn, causes the current to slow down as the overall water density decreases.
"We predict with high confidence the tipping to happen as soon as mid-century (2025–2095 is a 95% confidence range). These results are under the assumption that the model is approximately correct, and we, of course, cannot rule out that other mechanisms are at play, and thus, the uncertainty is larger," the study reads. "However, we have reduced the analysis to have as few and sound assumptions as possible, and given the importance of the AMOC for the climate system, we ought not to ignore such clear indicators of an imminent collapse."
This scenario has happened before. The last ice age took place around 120,000 years ago and lasted for around 100,000 years, When it ended, around 11,500 years ago, rapid glacier melt introduced substantial amounts of freshwater into the oceans. This caused a significant temperature rise of up to 27 degrees Fahrenheit, significantly impacting the planet's weather patterns and air temperatures.
"These were temperature changes over the North Atlantic region of 10 to 15 degrees in a decade," said Ditlevsen. "And that you can compare to the global warming we've seen of 1.5 degrees in a century. So this is a very rapid and strong climate change that we're looking at."
Scientists predict that the AMOC may come to a halt by the end of this century, with the possibility of collapsing even earlier, possibly within the next 20 to 25 years.
As the AMOC has only been continuously monitored since 2004, the precise effects of a collapse are not 100% known. However, researchers warn that its repercussions could be far-reaching, impacting tens of millions of people. These consequences could affect extremes of weather and severity of rainfall, disrupt growing regions, threaten coastal cities with increased sea level rise, and pose a major threat to agriculture.
"It is telling the farmers, you cannot grow the crops you're growing now because permanently you get, you know, five degrees colder temperatures," said Ditlevsen.
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