“In general, the rain falls more on the ocean,” says Earth systems scientist James Randerson, of the University of California, Irvine. This messes with the Walker circulation, sending sinking, relatively dry air over the South American landmass, leading to less rain over the Amazon. That water eventually falls as rain over the ocean. When that warm blob of water forms in the Pacific, it creates more evaporation, sending moist air into the sky. That’s because El Niño widely transforms atmospheric circulation. “In particular, over Amazonia suppresses the rain, and in general you can expect a widespread drought.” But, Jiménez-Muñoz cautions, “every El Niño is different-you can have different regional or local impacts.” “In 2015-2016, we observed that air temperature over Amazonia was the highest in maybe the last century,” says Juan Carlos Jiménez-Muñoz, a physicist and remote-sensing specialist at the University of Valencia.
But scientists recall how bad things got during the El Niño eight years ago. It’s still too early to tell when El Niño will arrive, and how severe it may end up being. And for the Amazon, that can cause drought. The past few years of cold “La Niña” conditions are weakening, potentially giving way to warm “El Niño” conditions later this year, according to modeling by the National Oceanic and Atmospheric Administration. The El Niño-Southern Oscillation is a Pacific Ocean phenomenon in which a band of water develops off the coast of South America that transitions from neutral to exceptionally cold or warm.
NICE CLOCK AMAZON DRIVERS
One of the drivers of Amazonian droughts may soon kick off, potentially piling yet more stress on an ecosystem already ravaged by the deforestation and fires caused by human meddling.
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