The role of the local and remote effects on the upwelling system variabilities along the western coast of South America, during El Niño / O papel de efeitos locais e remotos em variabilidades do sistema de ressurgência ao largo da costa oeste da América do Sul durante o El Niño

AUTOR(ES)
DATA DE PUBLICAÇÃO

2008

RESUMO

Off the western coast of South America, the coastal upwelling system presents an exceptional productivity, a result of the high efficiency of the biological ecosystem in converting the primary production into biomass. These chemical and biological processes are strongly modulated by the physical environment. For instance, during El Ni~no events the fishery productivity is strongly impaired in response to an inhibition of the coastal upwelling. In spite of this fact be widely known since pre-Colombian times, much doubts still persist about the mechanism by means of which the coastal system is affected by the large scale phenomena. The present work was idealized with the intention of contributing for this knowledge, studying how occurred the changes in the system during recent El Ni~no events, with emphasis on the intraseasonal scale. In this investigation, different methodologies of data analysis were used to identify the nature of the forcing which produced significant oscillations observed during the El Ni~no 1997-1998. Also, it was investigated if these oscillations were remotely forced and propagated along the coast as coastal trapped waves; what were their spatial and propagation properties. The first part of the work consists of an analysis of the temporal variability and the characterization of the low-frequency fluctuations occurred during the El Ni~no events. This analysis uses the wavelet spectrum applied to time series of sea level data collected off southern Equador, Peru and northern Chile. The cross wavelet spectrum and coherence spectrum were used to evaluate the relative importance of local and remote forcing of the sea level, associated with effects of the 1997-1998 El Ni~no. In the second part, the fluctuations remotely forced wer compared with results of simple linear models and with the model of Brink and Chapman (1987), in order to obtain the coastal trapped waves properties during that extraordinary El Ni~no event. One important conclusion of these analyses was the confirmation that the intraseasonal variability observed offo Peru during the 1997-1998 El Ni~no was, in part, the result of remote and local forcing, associated with equatorial waves and the wind effect, respectively.

ASSUNTO(S)

brinks model effects of el ni~no in the peruvian coastal upwelling ondas aprisionadas na costa modelo de brink wavelets. ondeletas. coastal trapped waves efeitos do el ni~no na ressurg^encia costeira do peru

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