Increased Amazon Basin wet-season precipitation and river discharge since the early 1990s driven by tropical Pacific variability

Bibliographic Data

ID15544142
AuthorsAndrew R Friedman (0000-0001-6994-2037, University of Bern, corresponding author), Massimo Bollasina (0000-0001-7509-7650, University of Edinburgh), Guillaume Gastineau (0000-0002-5478-1119, Centre National de la Recherche Scientifique), Myriam Khodri (0000-0003-1941-1646, Centre National de la Recherche Scientifique)
Year2020
Volume16
Issue3
Pages034033-034033
Publication date2020-12-22
Peer ReviewedYes
Open AccessYes
TypeARTICLE
VenueEnvironmental Research Letters (JOURNAL)
Journal identifiersISSN: 1748-9326 • E-ISSN: 1748-9326
PublisherIOP Publishing (PUBLISHER • GB)
DOI10.1088/1748-9326/abd587
OpenAlexW3116268466
LanguageEN
Citations received2
References cited82

The Amazon Basin, the largest watershed on Earth, experienced a significant increase in wet-season precipitation and high-season river discharge from the early 1990s to early 2010s. Some studies have linked the increased Amazon Basin hydrologic cycle to decadal trends of increased Pacific trade winds, eastern Pacific sea surface temperature (SST) cooling, and associated strengthening of the Pacific Walker circulation. However, it has been difficult to disentangle the role of Pacific decadal variability from the impacts of greenhouse gases and other external climate drivers over the same period. Here, we separate the contributions of external forcings from those of Pacific decadal variability by comparing two large ensembles of climate model experiments with identical radiative forcing agents but imposing different tropical Pacific wind stress. One ensemble constrains tropical Pacific wind stress to its long-term climatology, suppressing tropical Pacific decadal variability; the other ensemble imposes the observed tropical Pacific wind stress anomalies, simulating realistic tropical Pacific decadal variability. Comparing the Amazon Basin hydroclimate response in the two ensembles allows us to distinguish the contributions of external forcings common to both simulations from those related to Pacific trade wind variability. For the 1992–2012 trend, the experiments with observed tropical Pacific wind stress anomalies simulate strengthening of the Walker circulation between the Pacific and South America and sharpening of the Pacific–Atlantic interbasin SST contrast, driving increased Amazon Basin wet-season precipitation and high-season discharge. In contrast, these circulation and hydrologic intensification trends are absent in the simulations with climatological tropical Pacific wind stress. This work underscores the importance of Pacific decadal variability in driving hydrological cycle changes and modulating the hydroclimate impacts of global warming over the Amazon Basin

Amazon rainforest · Climatology · Geography · Meteorology · Pacific decadal oscillation · Precipitation · Sea surface temperature · Tropical Atlantic · Walker circulation · Wind stress · Climate variability and models · Cryospheric studies and observations · Environmental Science · Oceanographic and Atmospheric Processes · Geology