ARGO buoys deployments in the Eastern South-Pacific for the 2005-2007 period.
Motivation –Technique - Deployment sites.

Alexis Chaigneau, Gérard Eldin, Osvaldo Ulloa, Oscar Pizarro and Samuel Hormazabal

COPAS/PROFC
Cabina 7, Barrio Universitario
Concepcion, CHILE.

The Eastern South-Pacific (ESP) offshore Northern Chile and Peru is characterized by the presence of the most pronounced and extended oxygen minimum zone (OMZ) of the world ocean. Located at intermediate depths (<1000 m), this OMZ plays a crucial role on greenhouse gases (like CO2 and N2O) exchanges between the ocean and the atmosphere, but also on the adaptation of the ecosystems to such an anoxic environment. The ESP also exhibits a complex three-dimensional circulation and T-S structure, with the presence in the upper 2000 m of distinct water masses originating from equatorial, subtropical, subantarctic, and the Antarctic regions. Superimposed to these rather large-scale characteristics, the mesoscale activity is seen as an important factor for both the transfer of heat and salt from the offshore waters to the surface coastal layers, and for the offshore propagation of physical and biogeochemical properties from the coastal upwelling regions.

Despite its important physical and biogeochemical characteristics, the ESP is still relatively poorly sampled and badly known. In order to evaluate spatial distribution and variability of the OMZ and the water masses in the ESP, and to determine the vertical structure of the mesoscale eddies in this region, two independent but complementary international projects have led to funding of 30 ARGO buoys. Some of these floats (16-20) will be equipped with Aanderaa optode oxygen sensors. The deployments will take place between the end of 2005 and 2007 at different sites offshore the Peruvian and Chilean coasts.