Monthly mean coastal upwelling indices, west coast of South America, 1981 to 2000 trends and relationships
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Monthly mean coastal upwelling indices, west coast of South America, 1981 to 2000 trends and relationships
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  • Description:
    The Pacific Fisheries Environmental Laboratory (PFEL) upwelling index provides continuous proxy time series of coastal ocean processes which are difficult to measure directly and are infrequently available for the study of surface layer physical and biological ocean dynamics. The PFEL Upwelling Index (UI) is derived from analyzed pressure fields using planetary boundary layer theory and the geostrophic wind approximation to derive inferences about momentum transport from the wind to the sea surface layer. The UI values for the period January 1981 through December 2000 are analyzed for the highly productive upwelling systems off the coasts of Peru and Chile. These data have been extracted for two sets of 11 locations from 15° to 45°S. Large-scale characteristics of these time series include: 1) Highest UI values are in the austral spring and summer; 2) Maximum UI occurs earlier in the year at lower latitudes; 3) Mean UI is negative for short periods during austral winter; 4) Austral spring and summer UI increases from 45° to 30°S; 5) The largest UI values are found north and south of 21°S; 6) Variation in UI is dependent on computation point distance from shore and adjacent land topography; 7) Interannual variation increases three fold from south to north; 8) North of 24°S, greatest interannual variation occurs during the June to December period; 9) Interannual variability in UI approaches the magnitude of seasonal variability north of 24°S; and 10) Negative UI anomaly at 15°S, 18°S and 21°S increases in magnitude after 1994 and during El Niño-Southern Oscillation periods. The UI for the west coast of South America reflects physical environmental changes expected to influence temporally and spatially coincident ecosystems.
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