Monday 22 August 2005

P6

PM0075
Coastal upwelling off New Caledonia: a modelling and experimental approach
Vega, Andres¹, Rodier, Martine¹, Ganachaud, Alexandre¹, Lefevre, Jerome¹, Alory, Gael², Cresswell, George², Marchesiello, Patrick¹
1 Institut De Recherche Pour Le Development (IRD), New Caledonia
2 CSIRO Marine Research, Hobart, Tasmania, Australia
Author email: vega@noumea.ird.nc
Wind-driven coastal upwelling is an intense dynamical process affecting bio-chemical properties of the oligotrophic waters off New Caledonia. The seasonal upwelling appears clearly on SST and ocean colour (chlorophyll-a) satellite images during the austral summer along the western coast. The upwelling-related temperature variability can be modeled simply taking into account the wind stress, air-sea heat fluxes and climatological vertical thermal gradients. The Regional Ocean Model System (ROMS) was also applied to our region to reproduce the upwelling events and the associated phytoplankton blooms. A comparison between simulations, satellite and in situ data was made to validate the model for the period November-December 2004. The model reproduces the observed cooling events and generate a coherent 3-D dynamical structure. The coastal upwelling is mainly controlled by the wind stress but strongly influenced by largest scale processes. The scarce offshore observations show a biological response to upwelled waters: inshore waters present higher level of nutrients, chlorophyll-a and zooplankton biomass than offshore waters, during favourable upwelling conditions. However, the concentrations remain relatively moderate and the distribution patterns is complex.

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