The interaction between the Amazon rainforest and the AMOC

The Atlantic Meridional Overturning Circulation (AMOC) is a major component of the global ocean circulation and plays a crucial role in regulating Earth’s climate. Similarly, the Amazon Rainforest (ARF), often referred to as the “lungs of the planet”, is a key regulator of the global carbon and hydrological cycles. Both systems are considered to be climate tipping elements, characterised by the existence of multiple equilibrium states separated by a critical threshold. Anthropogenic climate change is pushing these systems closer to their respective tipping points, potentially leading to an AMOC slowdown or collapse and a transition of the Amazon from a rainforest to a savanna-like state.

While the AMOC and the ARF have been widely studied separately, their potential interactions remain poorly understood. Rising global temperatures are associated with reduced precipitation over the Amazon and a weakening of the AMOC. These coupled changes suggest two-way interactions, as AMOC weakening can decrease rainfall over the Amazon, while changes in Amazon vegetation can affect AMOC strength, potentially stabilising the climate system or triggering a tipping cascade. In this study, we investigate whether changes in the Amazon Rainforest can influence the stability of the AMOC.
We use the Community Earth System Model (CESM) to perform a set of numerical experiments in which the Amazon region is prescribed with different land-cover states, representing rainforest and grassland conditions. By comparing these experiments, we investigate the climate response to prescribed Amazon vegetation changes and their influence on large-scale atmospheric and ocean circulation.

Our results show that replacing rainforest with grassland leads to a global increase in near-surface air temperature, with the strongest warming occurring over the Amazon region. This transition is associated with pronounced changes in precipitation patterns and atmospheric moisture transport. These findings indicate a potential coupling between Amazon land-cover changes and large-scale climate dynamics, suggesting that Amazon tipping may have implications for AMOC stability.