Monday 22 August 2005

P6
1000-1230 hours

047
An upwelling-based temperature index off New Caledonia
Alory, Gael¹, Vega, Andres², Ganachaud, Alex², Cresswell, George¹
1 CSIRO, Hobart, Tasmania, Australia
2 IRD Noumea
Author email: gael.alory@csiro.au
An upwelling-based temperature index is built to investigate the main mechanisms of coastal upwelling off western New Caledonia. Intense upwelling events appear clearly on SST and chlorophyll-a satellite images during the austral summer along the western barrier reef of New Caledonia. A climatological analysis suggests that the seasonal intensification of the upwelling is related to an increase in trade wind strength and a shallowing of the mixed layer. A simple hindcast model of the coastal SST is constructed, taking into account the daily wind-induced vertical transport and air-sea heat fluxes, as well as seasonal variations of the vertical thermal gradient. Comparison of the hindcasted and observed temperatures over a 12-year period shows this upwelling index does a fairly good job. A sensitivity study helps to quantify the relative importance of the different processes. The geological, climatological and biological implications of the upwelling system are discussed.

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