Link Between AMOC Decline and Southern Amazon Rainfall Explored

Recent research conducted by the International Institute for Applied Systems Analysis (IIASA) has unveiled a significant relationship between the decline of the Atlantic Meridional Overturning Circulation (AMOC) and increased dry season rainfall in the Southern Amazon rainforest. This study, led by researcher Annika Högner and published in the journal *Environmental Research Letters* on June 9, 2025, emphasizes the complex interactions between critical climate systems and the urgent need for emission reductions to avert severe climate impacts.

The AMOC is a vital ocean current system that plays a crucial role in regulating global climate patterns. Its weakening, attributed to climate change, poses substantial risks not only to the North Atlantic region but also to ecosystems such as the Southern Amazon rainforest, which is facing increasing threats from deforestation and climate variability. According to the study, for every 1 million cubic meters per second of AMOC decline, the annual dry season rainfall in Southern Amazon increases by approximately 4.8%. This discovery suggests that while the weakening AMOC may temporarily buffer some of the anticipated dry season rainfall losses, it is not a sustainable solution to the broader climatic challenges faced by the region.

Högner notes, "The dry season is the most vulnerable time for the Amazon rainforest. Our findings reveal that a weakening AMOC contributes to increased rainfall in the Southern Amazon during this time, which may offset some of the drying trends observed. However, this is not an indication of improved climate conditions overall."

The complex relationship identified in the study also highlights that, despite the temporary increase in rainfall, the Amazon rainforest continues to experience longer and more intense dry seasons. Co-author Nico Wunderling, a professor at the Center for Critical Computational Studies (C3S) and scientist at the Potsdam Institute for Climate Impact Research (PIK), underscores the necessity of understanding these interactions for accurate climate risk assessments. He states, "The stabilizing interaction we found from the AMOC onto the Southern Amazon competes with other effects like those arising from deforestation and increasing temperatures, which would cause continued Amazon drying that the interaction will not be able to compensate for long-term."

The implications of this research extend beyond the Amazon rainforest. The findings reinforce the importance of integrating the interactions of tipping elements in climate risk assessments, particularly as they reveal that some interactions may stabilize while others exacerbate climate challenges. Högner asserts, "Interactions between climate-tipping elements are not just theoretical—they are happening now. We cannot count on the Earth system to continue absorbing the damage we cause. The only reliable way forward is to drastically reduce greenhouse gas emissions and limit warming."

This research is particularly timely as global climate change continues to escalate, underscoring the urgent need for international cooperation and policy measures aimed at reducing greenhouse gas emissions. The study adds a crucial piece to the puzzle of understanding climate dynamics and the interconnectedness of various ecological systems. As the world grapples with the realities of climate change, understanding these relationships will be essential in crafting effective environmental policies and strategies to mitigate the ongoing impacts of climate change.

In conclusion, while the study presents a nuanced view of the relationship between the AMOC and rainfall in the Southern Amazon, it serves as a stark reminder of the fragility of vital ecosystems in the face of climate change. The ongoing decline of the AMOC and its implications for the Amazon rainforest underscore the necessity of immediate action to address climate change and its cascading effects on global ecosystems. The full research findings are available in the *Environmental Research Letters* journal, providing further insights into this critical issue in climate science.