Science Source

Unprecedented drought over tropical South America in 2016: significantly under-predicted by tropical SST

States that tropical and sub-tropical South America are highly susceptible to extreme droughts
States that recent events include two droughts (2005 and 2010) exceeding the 100-year return value in the Amazon and recurrent extreme droughts in the Nordeste region, with profound eco-hydrological and socioeconomic impacts
States that in 2015–2016, both regions were hit by another drought
Shows that the severity of the 2015–2016 drought ("2016 drought" hereafter) is unprecedented based on multiple precipitation products (since 1900), satellite-derived data on terrestrial water storage (since 2002) and two vegetation indices (since 2004)
Finds that the ecohydrological consequences from the 2016 drought are more severe and extensive than the 2005 and 2010 droughts
Uses empirical relationships between rainfall and sea surface temperatures (SSTs) over the tropical Pacific and Atlantic to assess the role of tropical oceanic variability in the observed precipitation anomalies
Results indicate that warmer-than-usual SSTs in the Tropical Pacific (including El Niño events) and Atlantic were the main drivers of extreme droughts in South America, but are unable to explain the severity of the 2016 observed rainfall deficits for a substantial portion of the Amazonia and Nordeste regions
Concludes that this strongly suggests potential contribution of non-oceanic factors (e.g., land cover change and CO2-induced warming) to the 2016 drought