Wind relaxation and poleward flow events in the upwelling region off Baja California, Mexico

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Heriberto J Vazquez
Jose Gomez-Valdes

Abstract

Wind relaxation events are commonly observed in eastern boundary upwelling ecosystems. The wind fields over the southern part of the California Current System were separated into upwelling-favorable winds and wind relaxations by using a technique based on complex correlation analysis. Using vessel-mounted Acoustic Doppler Current Profiler and conductivity-temperature-depth observations from 4 consecutive Mexican Investigations of the California Current (IMECOCAL) cruises carried out during 2001–2002, a description of the ocean state associated with these stages of the wind field was elaborated for the northern Baja California (Mexico) upwelling region. Relaxation events occurred during each cruise. A coastal poleward flow event was conspicuous when a relaxation event followed a long upwelling favorable wind event. This pattern was also correlated with a negative or close to zero wind curl at the coast. A coastal equatorial jet and an upper-ocean offshore poleward flow were observed during spring, representing a typical upwelling pattern that is correlated with a large positive wind stress curl near the coast. In winter, a surface poleward flow was inhibited by a strong northwest wind event, which generated a shallow equatorward flow. The circulation patterns described here are consistent with theories that explain surface poleward flows through wind relaxation and negative wind curl.


Key words: winds, upwelling regions, poleward flows, wind relaxation events, IMECOCAL.

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Author Biographies

Heriberto J Vazquez, Scripps Institution of Oceanography

CASPO

Jose Gomez-Valdes, Centro de Investigación Cientifica y de Educación Superior de Ensenada

Investigador Titular, Departamento de Oceanografía Física.