Last year, a worrying study suggested that one of Earth’s major ocean currents was collapsing. Unfortunately, new data now confirms this.
“Changes in temperature, sea level and precipitation will severely affect society, and climate change is unstoppable on a human scale,” the authors of the latest study warn in an article for The Conversation.
It’s a terrifying prospect, and one of the most important elements of the new study is an early warning system, identified by Utrecht University oceanographer René van Westen and his colleagues.
This glimpse into the future could give the world at least some ability to prepare for what’s to come.
“We were able to develop an observable, physics-based early warning signal involving salinity transport at the southern edge of the Atlantic Ocean,” Van Westen and his team explain.
The Atlantic Southern Overturning Circulation (AMOC) is a large system of ocean currents that transfers warm salty water northward. This water cools on its winding journey north, making it denser. As cold water sinks, water from other oceans is drawn in to fill the surface.bringing the circulatory system south again.
AMOC has seen a considerable slowdown since the mid-1900s.
With increased freshwater inputs from melting glaciers and increased rainfall, salt concentrations in seawater decrease and salt water becomes less dense, disrupting the sinking process and weakening the entire physical cycle.
Now, by modeling these ocean systems, van Westen and his colleagues have found a way to detect when the AMOC’s “tipping point” is near: salinity decline will slow at the southern edge of the Atlantic.
“Once a threshold is reached, the tipping point will likely occur within one to four decades,” the authors say.
The AMOC has only been directly monitored since 2004, so not long enough to understand the full trajectory of the current slowing trend. As a result, scientists use proxy indicators such as salinity levels to try to fill gaps in their knowledge.
Van Westen and his team have not yet merged all the factors to accurately predict when the AMOC collapse will occur, but they believe the catastrophic moment is much closer than many current simulations suggest .
The new modeling explores the freshwater-induced tipping point itself, rather than trying to predict its timing. But the resulting data suggests that the AMOC is much more sensitive to changes than most climate models have accounted for.
“The new study confirms past concerns that climate models systematically overestimate the stability of the AMOC,” Stefan Rahmstorf, a climatologist at the University of Potsdam, who was not involved in the study, told RealClimate.
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The AMOC impacts much of the Earth’s climate, so it is one of the tipping points in the Earth’s climate system that concerns researchers most. The collapse of the AMOC occurs cyclically on a scale of a million years, and based on past events we know that the Arctic is expected to expand southward during this period, resulting in a drop in temperatures in northwest Europe of up to 15°C, disrupting tropical monsoons and warming. the southern hemisphere even further.
The ensuing chain of reactions will have serious consequences for entire ecosystems and global food security.
“The new study adds significantly to growing concerns about a collapse of the AMOC in the not too distant future,” Rahmstorf told the Associated Press. “We will ignore this at our peril.”
This research was published in Scientists progress.