California Current System During the Last Six Centuries: Response to Abrupt Climatic Changes

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Varved sediment in the Santa Barbara Basin is a unique recorder of temperate-subarctic and subtropical flora and fauna which preserves an annual signal through anaerobic deposition. Effects of climatic change are greatly magnified by fluctuations in the productivity of surface waters and of preservation at the seafloor. For example, the introduction of subtropic biota during strong El Nino events coincides with decreased bioproductivity in the photic zone and with increases oxygenation of the otherwise anoxic bottom waters. In this interdisciplinary research project sediment cores from Santa Barbara Basin off California will first be studied by physical and chemical means to identify periods, within the last 600 years, when climate changed rapidly of fluctuated strongly. These abrupt changes will then be scrutinized in detail, for changes in diatom flora and foraminiferal fauna, both planktonic and benthic, and for shifts in geochemical and isotopic parameters. The resulting multidisciplinary time series are to be interpreted in terms of changes in the oceanographic conditions of the California Current, using calibrations worked out previously. The results are to be compared with information from tree rings and ice records from North America and other regions of the Northern hemisphere. The aim is to assess the frequency of unusual events in the past, their expression in the California Current as far as it can be read from its varved record, and the teleconnections, if any, with climatic changes elsewhere.