It has a difficult name, and is probably unknown to most people, except among professionals, but it plays a fundamental role in the climatic balance of our planet. We are talking about the southern overturning of the Atlantic circulation, also known by the acronym Amoc. A current that crosses the entire Atlantic Ocean, bringing the warm water of the tropics to the north, the cold water of the arctic regions to the south, and shaping the climate of all the areas it passes through (and not only). Recently the scientific community has begun to fear that this “highway of the seas” is increasingly at risk due to global warming, with effects that could prove catastrophic. An example? The collapse of the AMOC could lead to the disappearance of large parts of the Amazon forest, creating a vicious circle that would further accelerate the impact of climate change on our planet.
The collapse of the Atlantic currents could destroy the Amazon forest
The prediction comes from research just published in Nature Geoscience, which studied the impact that a reduction in the intensity of Amoc would have on rainfall affecting the Amazon, and the effects that this would, in turn, have on the vegetation of the Amazon. its immense rainforest. To do so, they looked to the past: to a period of the last glaciation in which a phenomenon known as the Heinrich event, i.e. the calving of enormous icebergs pouring fresh water into the Atlantic Ocean, drastically slowed down the meridional overturning of the Atlantic circulation to several thousand years.
Thanks to a core sample of marine sediments collected at the mouth of the Amazon River, researchers were able to study the pollen and residues of organic material transported by the great river that crosses the Amazon over the last 25 thousand years. And in this way, they reconstructed the changes that the vegetation of the rainforest underwent between 18 and 14 thousand years ago, corresponding to the Heinrich event of the last glaciation.
The researchers’ analyzes indicate that the event produced a sharp decline in the rainforest in the northernmost regions of the Amazon. A situation to which the rainforest, as a whole, managed to adapt, then returning to thrive and expand when the climatic conditions became favorable again. At the time, however, the Amazon forest had to face a single challenge, namely the drying up of the northernmost regions. While today it is put at risk by a multitude of new dangers, which all together risk overcoming even the resilience of the largest green lung on our planet.
“Our data shows that the Amazon ecosystem has in the past been able to adapt to changes in precipitation patterns resulting from a weakening of the meridional overturning of the Atlantic circulation,” explains Stefan Mulitza, a researcher at the Center for Marine Environmental Sciences at University of Bremen, among the authors of the study. “However, a weakening of the AMOC in the future would occur simultaneously with an increase in deforestation, and this could compromise the stability of this very important global system. The models we used also show that AMOC does not have to collapse completely to have an effect on the rainforest: even a moderate slowdown of AMOC could have a huge impact on the northern areas of the Amazon region.”