The 2005 Amazon Drought

node · earth · Western and southwestern Amazon Basin

A severe drought concentrated in the western and southwestern basin, described at the time as a once-in-a-century event. Its driver was unusual and instructive: it was not an El Nino drought. It was associated with anomalously warm sea surface temperatures in the tropical North Atlantic, which shifted the convergence zone north and left the southwestern Amazon without its wet season. Rivers in Acre and the upper Madeira fell to record lows, communities were stranded, and fire escaped into standing forest on a large scale. Its scientific importance came from the RAINFOR long-term plot network, which had been measuring the same trees for years before the drought struck and could therefore measure what it did rather than infer it. Phillips and colleagues reported in 2009 that the drought reversed the forest's long-standing carbon sink, turning it into a source - the first direct field demonstration that the Amazon's role in the carbon cycle is conditional on rainfall rather than guaranteed by it.