Enhanced Atlantic freshwater export during El Niño

Using two reanalysis data sets, the influence of El Niño/Southern Oscillation (ENSO) on the surface freshwater balance of the Atlantic ocean is examined. We present evidence that the transport of water vapour out of the tropical Atlantic is enhanced during warm ENSO phases, while it is reduced during cold phases. These tropical changes alter the freshwater budget of the entire Atlantic drainage basin. The difference in freshwater export between La Niña and El Niño years is on the order of 0.1 Sv (1 Sv=10 ms) for the entire Atlantic. Results from an idealized coupled ocean-atmosphere model suggest that this amplitude is of significance for the strength of the North Atlantic thermohaline ocean circulation, if the persistence of the anomaly is on the order of decades.