Abstract

Recent high-resolution hydrographic measurements (1976-2001) from the eastern South Pacific (ESP) were employed combined with highresolution data from the World Ocean Circulation Experiment to evaluate the vertical and horizontal extension of the OMZ (oxygen minimum zone, < 20 ?mol kg -1) there. Of the six permanent hypoxic regions in the world oceans, the ESP OMZ is volumetrically the fourth largest, occupying 2.74 x 10 6 km 3 and accounting for ?11% globally. Examples of variability in the vertical position of the OMZ in the water-column and also in its intensity offshore central Chile will be addressed. We conclude that the OMZ in the ESP is partly based on old, low-oxygen waters from intermediate depths of the North Pacific Ocean, which were further depleted of oxygen off Mexico and Peru, advected into the region along the eastern Pacific coast. Coastal upwelling zones along the eastern Pacific combined with general circulation thus might provide a mechanism that allows the renewal of upper Pacific Deep Water, the oxygen poorest and oldest water mass of the world oceans. © 2007 Universidad de Concepción.