A slight weakening of one of Earth major ocean currents could trigger dramatic declines in rainfall across the Amazon and other tropical rainforests, sparking droughts that could accelerate global climate change, according to new research published in Nature.
The study focuses on the Atlantic Meridional Overturning Circulation (AMOC) a system of ocean currents that includes the Gulf Stream. Often described as Earth’s climate conveyor belt, the AMOC redistributes heat and nutrients between the Northern and Southern Hemispheres. But scientists now warn that even a mild slowdown could cut rainfall over some rainforest regions by up to 40%, with the Amazon particularly at risk.
“This is bad news,” said Pedro DiNezio, lead author and climate scientist at the University of Colorado Boulder. “The Amazon rainforest holds nearly two years’ worth of global carbon emissions. If drought hits this region, it could release vast amounts of carbon back into the atmosphere — feeding a vicious loop of warming and further ecosystem collapse.”
The AMOC is already showing signs of weakening, partly due to glacial meltwater entering the Atlantic as global temperatures rise. While a full collapse is still considered unlikely, historical climate data shows that the AMOC has switched off in the past, leading to abrupt and severe climate shifts.
To understand the long-term risks, researchers analyzed 17,000-year-old climate records, including ancient rainfall patterns preserved in caves and sediments. When plugged into modern climate models, the results consistently pointed to a future where a weaker AMOC would cool the tropical Atlantic, shifting weather systems and drying out large swaths of rainforest.
The projected decline in rainfall could devastate biodiversity, dry out peatlands, and cripple the Amazon ability to act as a carbon sink a vital buffer against climate change.
Still, the scientists remain cautiously optimistic. “We still have time,” DiNezio emphasized. “But only if we act fast decarbonizing the economy and ensuring that green technologies are made widely accessible.”
Without decisive action the weakening of Earth ocean engines may unleash climate feedback loops beyond our control transforming the world’s rainforests from carbon absorbers into carbon emitters, and reshaping global climate in the process.