Speed of system’s collapse makes adaptation impossible.
A study reveals the Atlantic Ocean’s circulation nearing a critical tipping point, posing dire implications for the climate system and humanity. Researchers, startled by the projected collapse speed, developed an early warning system for the breakdown of the Atlantic meridional overturning circulation (AMOC), a crucial component in global climate regulation, though they cannot yet determine its imminent occurrence.
The researchers discovered that AMOC is currently progressing towards a sudden change, a phenomenon not witnessed in over 10,000 years, with severe consequences for vast regions of the globe.
AMOC, incorporating segments of the Gulf Stream and other robust currents, functions as a maritime conveyor belt transporting heat, carbon, and nutrients from the tropics towards the Arctic Circle. Upon reaching the Arctic, the conveyed materials cool and descend into the depths of the ocean. This dynamic process aids in the global distribution of energy and moderates the effects of anthropogenic global warming.
However, the system is being undermined by the faster-than-anticipated melting of Greenland’s glaciers and Arctic ice sheets. This influx of freshwater into the sea impedes the sinking of saltier, warmer water from the south.
Previous research indicates that AMOC has decreased by 15% since 1950 and is currently at its weakest point in over a thousand years. This finding has sparked discussions regarding the likelihood of an impending collapse.
Until now, there has been no consensus on the severity of the potential collapse. A study from last year, based on changes in sea surface temperatures, suggested that the tipping point could occur between 2025 and 2095. However, the UK Met Office stated that significant, rapid changes in AMOC were “very unlikely” in the 21st century.
The newly published paper in Science Advances breaks new ground by examining warning signs in the salinity levels at the southern boundary of the Atlantic Ocean, stretching from Cape Town to Buenos Aires. By simulating changes over a 2,000-year period using computer models of global climate, the study reveals that a gradual decline could lead to a sudden collapse in less than 100 years, resulting in catastrophic consequences.
The paper asserts that the findings offer a definitive response regarding the possibility of such an abrupt shift, stating, “This is alarming news for the climate system and humanity. Previously, it might have been assumed that the tipping of AMOC was merely a theoretical concept and that the tipping would vanish once the full climate system, with all its additional feedbacks, was considered.”
Furthermore, the paper delineates some of the ramifications of an AMOC collapse. Certain regions in the Atlantic would experience a one-meter rise in sea levels, leading to the inundation of numerous coastal cities. The Amazon’s wet and dry seasons would reverse, potentially pushing the already fragile rainforest beyond its tipping point. Global temperatures would exhibit significantly more erratic fluctuations. The southern hemisphere would experience increased warmth, while Europe would undergo dramatic cooling and reduced rainfall. Although this cooling trend might seem appealing compared to the current warming trend, the changes would occur ten times faster, rendering adaptation nearly impossible.
René van Westen, the lead author of the paper from Utrecht University, remarked, “What caught us off guard was the speed at which tipping occurs. It will be catastrophic.” He added that there is currently insufficient data to determine whether this will transpire in the next year or over the coming century. Nonetheless, once it occurs, the changes are irreversible on human timescales.
Meanwhile, the trajectory is undeniably concerning.
We are progressing towards it. That’s rather alarming,” van Westen remarked. “We must treat climate change with much greater urgency.
