Net primary productivity, upwelling and coastal currents in the Gulf of Ulloa, Baja California, México

E González-Rodríguez,A Trasviña-Castro,L Zamudio,G Gaxiola-Castro,R Cervantes-Duarte

doi:10.5194/os-8-703-2012

Abstract

Abstract. The Gulf of Ulloa, a highly productive area off the western coast of the Baja California Peninsula, is examined for five successive years (2003–2007) by using satellite data and seasonal net primary productivity (NPP) estimates obtained from a vertical generalised production model. The results identify that northwestern winds blow parallel to the coast throughout the year. However, highest NPP occurs from March to June. During this period, an equatorward coastal current transports water from neighbouring upwelling areas to the northern Gulf of Ulloa and in combination with local upwelling, which injects nutrients into the euphotic zone, produce the observed increase in NPP. The opposite situation occurs in late summer when a warm poleward current of tropical characteristics arrives and inhibits the productivity in the whole region and generates the yearly lowest NPP levels. Our findings reveal the importance of lateral advection in the modulation of the primary productivity in this subtropical upwelling region.

Highlights

The Gulf of Ulloa (Fig. 1) is in the shallow sea off the west coast of the Baja California Peninsula limited to the north by Punta Eugenia (28◦ N 115◦30 W) and to the south by Bahıa Magdalena (25◦ N 111◦30 W)
The highest levels of net primary productivity (NPP) are found from March through June, when a combination of positive wind stress curl (WSC), lowest yearly sea surface temperature (SST) values and equatorward currents carrying cold nutrient rich water occur throughout the coastal region
During July a transition occurs in the southern half of the California Current, as described in many CALCOFI reports

Summary

Introduction

The Gulf of Ulloa (Fig. 1) is in the shallow sea off the west coast of the Baja California Peninsula limited to the north by Punta Eugenia (28◦ N 115◦30 W) and to the south by Bahıa Magdalena (25◦ N 111◦30 W). The whole CC region is characterized by the presence of meanders, eddies and a coastal transition zone (CTZ) between it and the coastal waters during upwelling season This CTZ contains large filaments associated with flowing squirts or jets (Davis, 1985; Rienecker and Mooers, 1989; Thomson and Papadakis, 1987), and eddies that contribute to the offshore transport of properties (Brink and Cowles, 1991) such as heat, nutrients, oxygen, chlorophyll, and salinity (Roemmich, 1989; Bograd et al, 2001)

Methods

Results

Conclusion