Regional applications of observations in the eastern Pacific: Western South America

Abstract

El Niño is the main source of climate variability in the tropical Pacific ocean and it is particularly dramatic along the western coast of South America, where monthly sea surface temperature anomalies during the peak of the 1982-83 and 1997-98 events have been on the order of 9°C. The local warming favors a southward displacement of the ITCZ, which results in dramatic increase in rainfall on the coasts of northern Peru, Ecuador, producing significant losses in infrastructure and economical activities associated with flooding. Also, the tropicalization of the coastal upwelling environment of Peru and Chile produces disruptive effects on the ecosystem and associated fisheries. Decadal variability in the equatorial Pacific is closely linked to variability along western South America. Recent manifestations include the abrupt warming around 1976 throughout the eastern Pacific, which was followed by a cool period since the late 1990s. Similar to El Niño, this variability also impacts climate along the coast and the marine ecosystems. The dynamics of this variability, however, is poorly understood at present. A similar issue is related to climate change, and its potential influence associated with equatorial dynamics and local air-sea interactions along the coast. These relationships are not well understood at present. Key needs in the region are the enhancement of subsurface monitoring in the far eastern equatorial Pacific and along the coast of South America, and the reduction of long-standing biases in the mean and the variability in climate models in the eastern Pacific, guided by process understanding, to provide reliable climate forecasts on intraseasonal to decadal scales, and climate change projections for the eastern Pacific and its feedbacks and impacts on global climate.