Visualization of Atlantic Currents Based on Sea Surface Temperature Data
NASA/Goddard Space Flight Center Scientific Visualization Studio
Research indicates that a potentially disastrous collapse of the Atlantic Current—a crucial climate regulator for Europe—may be inevitable. Model forecasts suggest a 10 to 23 percent chance of this collapse becoming permanent.
“We are already on the brink of collapse, and even now, nothing can alter that,” states Phil Holden from the Open University, UK.
The Atlantic Meridional Overturning Circulation (AMOC) is vital for transporting warm, salty waters from the tropics to the North Atlantic. Here, the water cools, sinks, and travels south, regulating climate across Europe, Africa, and the Americas.
Recent observations reveal signs of weakening in this critical system, particularly a slowdown in specific regions. Factors such as Greenland melting and climate change are contributing, resulting in less dense saltwater that hampers the rate of subsidence.
Scientists warn that if AMOC collapses, Europe may face near-Arctic conditions, while global monsoon systems could weaken. A recent study suggests AMOC may reach a tipping point within a few decades, although estimating the likelihood remains challenging.
“Currently, the collapse of AMOC is somewhat invisible,” Holden remarked. “We lack clear predictions concerning the timing and quantification of such events.”
“There are abundant uncertainties and differing views within the scientific community,” adds Tim Renton from the University of Exeter, UK.
To enhance understanding of the AMOC’s dynamics, Holden, Renton, and their colleagues conducted 21 computer simulations from 2005 to 2135, varying rates of Greenland ice melt and peak emissions. The team anticipates that greenhouse gas emissions will decline to net zero over 35 years post-peak, with a consistent rate of ice melt.
Under conservative scenarios predicting peak emissions by 2025 and only 54 millimeters of sea-level rise from the Greenland ice sheet by 2100, there is already a 10 percent chance of AMOC collapse. This is defined as a circulation that occurs solely at lower latitudes, with reversed currents ceasing to deliver heat to higher latitudes.
Models predict that failing to commence a net-zero trajectory by 2100 could escalate the collapse probability to 80 percent.
Conversely, melting Greenland ice may raise sea-level rise predictions to 274 mm by 2100, which could increase the collapse probability to 23 percent.
Even with an inevitable collapse, it will take considerable time. Simulations show the average delay from the onset of collapse to its manifestation is about 84 years, with the earliest occurrence around 2060.
Tackling the notion of a “committed collapse,” Up to Wagner views this framing as useful for risk management. Yet, applying this to reality is complex. “There’s strong evidence of weakening, yet major mechanical consequences remain uncertain,” he cautioned.
According to Jonathan Baker from the UK’s Met Office, the simulation offers valuable insights into AMOC’s response to various conditions. However, the model’s lower resolution may affect risk estimates compared to other high-resolution climate models.
While state-of-the-art climate models operate on a 1° grid, extensive computations are required for long-term simulations. The chosen model for this study uses a 5° grid, a strategic decision due to computational limitations.
“Previous technology didn’t allow for high-resolution models,” Renton explained. Although lower resolution raises risk estimates, recent research indicates that higher resolutions may increase, rather than diminish, the estimates.
“Further investigations employing various climate models alongside broader evidence are crucial before drawing solid conclusions about potential AMOC collapse risks,” Baker emphasized.
If the world is progressing toward AMOC collapse, as modeled, it underscores the urgent need for emission reductions. Renton asserts that delaying net-zero commitments will significantly raise the probability of collapse. A ten-year delay may lead to an average collapse timeframe of 57 years instead of 84 years.
“What this model conveys is a pressing need to accelerate our journey to net-zero emissions and maintain the collapse risk at 10%,” Renton urged.
This aligns with recent studies indicating that AMOC’s slowdown could be reversed if carbon emissions are effectively reduced.
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Source: www.newscientist.com
