Abstract
Tropical and sub-tropical South America are highly susceptible to extreme droughts. 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. In 2015–2016, both regions were hit by another drought. Here, we show 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). The ecohydrological consequences from the 2016 drought are more severe and extensive than the 2005 and 2010 droughts. Empirical relationships between rainfall and sea surface temperatures (SSTs) over the tropical Pacific and Atlantic are used to assess the role of tropical oceanic variability in the observed precipitation anomalies. Our 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. This strongly suggests potential contribution of non-oceanic factors (e.g., land cover change and CO2-induced warming) to the 2016 drought.
Highlights
Greenhouse warming is anticipated to change drought outlook in the future climate[1,2,3] and enhance drought severity in particular[4]
Over the two sub-regions of Amazonia, the 2016 drought peaked in the SPI peaked once at the beginning (SON) and DJF seasons with short term (3 and 6 month) Standardized Precipitation Index (SPI) values close to the extreme drought level of −2 (Fig. 1a and b), which were record lows for the study period (1982–2017)
Over North Amazon, the SPI values in 2016 are comparable with the record low values for the region during the 1992 and 1998 events. These statements are valid for SPI analysis over the 1901–2017 period (Figure S2)–the SPIs calculated for 2016 show the worst drought ever recorded over South Amazon and Nordeste since 1901 with only two other droughts (1904 and 1916) reaching a similar level of severity
Summary
Greenhouse warming is anticipated to change drought outlook in the future climate[1,2,3] and enhance drought severity in particular[4]. Subsequently reducing moisture convergence and weakening convection over the Amazon and Nordeste regions This warming causes an anomalous rising motion in the north which is coupled with an anomalous sinking motion over South America and the Southern Atlantic (by the Hadley circulation) further reducing rainfall over the subsidence zone[8, 12, 15, 18]. Over the Nordeste region, anomalously warmer SSTs in the tropical Pacific and Atlantic were expected to intensify drought conditions that had been persisting since 20126, 10; over the Amazon basin, preliminary analysis of the 2015–2016 wet season confirmed a severe drought condition[17].
Sign-in/Register to view highlights & summary Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
