Study lead author, Dr Jonathan Barichivich, from Universidad Austral de Chile and former Research Fellow from the University of Leeds, said: "Increases of severe droughts in the Amazon have received a lot of attention by researchers. However, what really stands out from this long-term river record is the increase in the frequency and severity of the floods. With a few minor exceptions, there have been extreme floods in the Amazon basin every year from 2009 to 2015."
According to the study, the increased flooding is linked to a strengthening of the Walker circulation -- an ocean-powered system of air circulation caused by differences in temperature and pressure over the tropical oceans. This system influences weather patterns and rainfall across the tropics and beyond.
Co-author Professor Manuel Gloor, from the School of Geography at Leeds, said: "This dramatic increase in floods is caused by changes in the surrounding seas, particularly the Pacific and Atlantic oceans and how they interact. Due to a strong warming of the Atlantic Ocean and cooling of the Pacific over the same period, we see changes in the so-called Walker circulation, which affects Amazon precipitation.
"The effect is more or less the opposite of what happens during an El Niño event. Instead of causing drought, it results in more convection and heavy rainfall in the central and northern parts of the Amazon basin."
https://www.sciencedaily.com/releases/2018/09/180920075857.htm
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