Inter-hemispheric eco-climatic connections in the Americas: A possible influence of a longer dry season over the Amazon forests on the North American monsoon

Abstract:

Recent studies have identified a lengthening of the dry season over the southern Amazon during the last three decades. This work suggests that this lengthening is correlated with an earlier demise of the North American monsoon, mainly observed after the mid 1990’s. In addition, changes in both systems appear to be induced by common forcing factors at different time scales, like the shifting patterns of El Niño-Southern Oscillation anomalies, the westward expansion of the North Atlantic Subtropical High, and the global warming influence. However, whether the observed changes of dry season rainfall deficit over the Amazonia could influence the retreat of the North American monsoon is not clear. This work aims to identify the processes that could enable a possible influence of a longer and stronger dry season in the Amazon forests on the cross-equatorial flow and the demise of the North American monsoon. To address this possible inter-hemispheric link may be important in understanding the future climate variability of the American monsoons when the effects of anthropogenic forced change and conversion from Amazon forests to savannah become more dominant. The latter would be particularly relevant in order to understand the role of ecosystem changes on modulating climate over the Americas.