Atmospheric events disrupting coastal upwelling in the southwestern Caribbean

Abstract

Year‐round coastal upwelling is a prevalent phenomenon in the southwestern Caribbean region, driven by northeast trade winds. This pattern can be disrupted during the boreal winter‐to‐spring transition by event‐scale departures in the pressure systems, characterized by a change in wind direction to northward, with the accompanying relaxation of coastal upwelling. To study these poorly understood events, regional atmospheric and data‐assimilative ocean modeling experiments were carried out for the period 4 March to 9 April 2003 and compared to shipboard observations This combined ocean‐atmosphere approach allowed us to study the evolution of a 3‐day atmospheric disturbance affecting ocean currents and collapsing the upwelling pattern against the Colombian coast along the Guajira Peninsula near 12°N. The southward extension of the coastal upwelling, which normally reaches 10.5°N, was blocked by the warmer and slightly lower salinity waters of the cyclonic Panama‐Colombia gyre. Under typical conditions, the ocean model and shipboard observations of temperature and salinity profiles were in good agreement with each other, both at coastal and oceanic stations. The presence of a low‐level westward wind jet was manifested in the atmospheric model simulation, confirming that it promotes the Guajira upwelling system; however, the jet vanishes under disturbed atmospheric conditions.