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Modern Upwelling Systems and Palaeo-Upwelling Criteria |
1 Institute of Biogeochemistry and Marine Chemistry, University of Hamburg, Bundesstraße 55, D-2000 Hamburg 13, Germany
2 National Institute of Oceanography, Dona Paula, 403 004 Goa, India
Time series sediment traps have been deployed since May 1986 in the Arabian Sea and since October 1987 in the Bay of Bengal. The results of one and a half years from the western, central, and eastern Arabian Sea and of one year from the northern Bay of Bengal show that particle flux patterns are related to the strong monsoon winds and heavy rains. Particle flux maxima in the Arabian Sea are mainly related to wind-induced deeper mixing and nutrient enrichment of surface waters during the SW and NE monsoons. Extremely high particle fluxes with high biogenic opal contents during the SW monsoon at the western location show that it is reached by nutrient-rich water from the near-shore upwelling centres. In the northern Bay of Bengal, particle flux maxima coincide with the period of maximum discharge of the Ganges and Brahmaputra rivers during which river plumes enriched in nutrients are advected into offshore areas. Additionally, the winds and river plumes supply enormous amounts of mineral matter during the periods of high productivity and high particle fluxes. The interaction between marine-biogenic material with eolian and fluviatile mineral particles plays a key role in sedimentation. The incorporation of mineral matter into biologically formed aggregates ensures their rapid sedimentation and thus enhances the removal of biologically fixed atmospheric carbon dioxide to the deep sea.
