Amazon precipitation response to an AMOC shutdown in a km-scale atmospheric model

The Atlantic Meridional Overturning Circulation (AMOC) is considered one of the Earth’s climate tipping elements. Concerns have been raised that global warming could increase the freshwater input into the North Atlantic at high northern latitudes and thereby abruptly interrupt the deep water formation that fuels the AMOC’s lower limb and is necessary to maintain the overturning. To assess the risks such an AMOC tipping scenario poses to societies, it is essential to understand how an AMOC collapse feeds back into the climate system as a whole. It is of particular interest whether an AMOC tipping would have a stabilizing or destabilizing effect on other climate tipping elements. In this context, we studied the impact of an AMOC shutdown on the Amazon Rainforest, which is itself thought to be at risk of undergoing a transition to a savanna state. We forced a km-scale atmosphere-only model with sea surface temperatures from a second lower-resolution coupled climate model simulation that features a collapsed AMOC state. Previous studies indicate that land-atmosphere interactions are different in such convection-resolving models compared to CMIP-type models, possibly affecting the response of precipitation to large-scale perturbations. In general, our simulation confirms the global AMOC-collapse induced precipitation and temperature anomaly patterns also seen in coupled climate model hosing experiments. Most prominently these comprise a cooling and drying of the North Atlantic region and a corresponding southward shift of the tropical rainbelt. However, upon closer examination, we find that over land the signal is attenuated, and in particular precipitation patterns over the Amazon Rainforest appear to be remarkably robust against an AMOC shutdown. This, in turn, means that a tipping of the AMOC would to a first degree neither have a stabilizing nor destabilizing effect on the Amazon Rainforest.