IGPP Seminar Series

Oceanic downscaling and upscaling effects in the Peru/Chile upwelling system

by Francois Colas
Atmospheric and Oceanic Sciences UCLA

Abstract

Oceanic eastern boundary upwelling regions are notable for several reasons: they are the most productive ecosystems in the ocean, their dynamics can be strongly modulated by large-scale signals (downscaling effects) and it was recently shown that they are a large source of bias in climate model solutions (upscaling effects). In addition, in these regions, which generally have a weak mean circulation, eddies are an essential component of the dynamics. The emphasis is put on the Peru/Chile region. Its direct connection with the equatorial region makes it an excellent model testbed for the downscaling of Pacific signals. Using a regional ocean numerical model (ROMS), we first illustrate downscaling effects on the regional dynamics, focusing on the strong 1997/98 El Nino event. The upwelling intensity appears to be controlled by a complex interplay between coastal waves, local wind, cross-shore geostrophic flow and water-mass large-scale distributions. Second, the role of mesoscale eddy activity and the importance of the nearshore wind structure are discussed and illustrated in terms of heat balance and consequent possible upscaling effects.
Tuesday, 14 April 2009
3853 Slichter Hall
Refreshments at 3:45 PM
Lecture at 4:00 PM