El Niño phase transition by deforestation in the Maritime Continent

Abstract

El Niño-Southern Oscillation (ENSO), an irregular alternation between warm El Niño and cold La Niña phases, is the most prominent air-sea interaction phenomenon on Earth and greatly affects global weather and climate. Nevertheless, it remains unclear whether human activity can alter the characteristics of ENSO. We demonstrate, using reanalysis data and coupled general circulation models, that deforestation over the Maritime Continent (MC) favors a rapid transition of El Niño to La Niña. Deforestation over the MC can induce a regional enhancement in precipitation, which in turn leads to the strengthening of the easterly trade winds over the western equatorial Pacific owing to the Gill-response. These stronger trade winds, by inducing a shoaled thermocline in the eastern Pacific, are favorable for the development of cold sea surface temperature anomalies in the eastern equatorial Pacific during El Niño decaying years. Our results suggest that El Niño is more likely to be followed by La Niña if MC deforestation continues in the future.