The Atlantic meridional overturning circulation (AMOC) and the Amazon forest are viewed as connected tipping elements in a warming climate system. If global warming exceeds a critical threshold, the AMOC may slow down substantially, changing atmospheric circulation and leading to Amazonia becoming drier in the north and wetter in the south. Yet, the impact of an AMOC slowdown on Amazon vegetation is still not well constrained. Here we use pollen and microcharcoal data from a marine sediment core to assess changes in Amazon vegetation from 25,000 to 12,500 years ago. Additionally, we model vegetation responses to an AMOC slowdown under both glacial and pre-industrial conditions. During a past AMOC slowdown (Heinrich Stadial 1–18,000 to 14,800 years ago), pollen data evidence a decline in cold- and moist-affinity elements, coupled with a rise in seasonal tropical vegetation. This pattern is consistent with the decline in suitability of northern Amazon moist forests in a model with an imposed 50% AMOC weakening under glacial conditions. Our modelling results suggest similar changes for a comparable AMOC slowdown under pre-industrial conditions. Combined with current disturbances such as deforestation and wildfires elsewhere in the basin, an AMOC slowdown may exert a systemic impact on the Amazon forest.

大西洋经向翻转环流 （AMOC） 和亚马逊森林被视为气候变暖系统中相互关联的倾翻因素。如果全球变暖超过临界阈值，AMOC 可能会大幅减慢，改变大气环流，导致亚马逊北部变得更干燥，南部变得更潮湿。然而，AMOC 放缓对亚马逊植被的影响仍然没有得到很好的限制。在这里，我们使用来自海洋沉积物核心的花粉和微木炭数据来评估 25,000 至 12,500 年前亚马逊植被的变化。此外，我们还模拟了冰川和工业化前条件下植被对 AMOC 减慢的响应。在过去的 AMOC 放缓期间（Heinrich Stadial 1-18,000 至 14,800 年前），花粉数据证明寒冷和潮湿亲和元素下降，同时季节性热带植被增加。这种模式与在冰川条件下施加 50% AMOC 减弱的模型中亚马逊北部潮湿森林适宜性下降一致。我们的建模结果表明，在工业化前条件下，类似的 AMOC 放缓也发生了类似的变化。结合当前流域其他地方的森林砍伐和野火等干扰，AMOC 放缓可能会对亚马逊森林产生系统性影响。