Gruber, N, , IGPP, UCLA, Los Angeles, USA, ngruber@igpp.ucla.edu
Frenzel, H, , IGPP, UCLA, Los Angeles, USA, hfrenzel@igpp.ucla.edu
McWilliams, J, C, IGPP, UCLA, Los Angeles, USA, jcm@atmos.ucla.edu
Plattner, G, K, IGPP, UCLA, Los Angeles, USA, plattner@igpp.ucla.edu
Marchesiello, P, , Institut de Recherche pour le Developpement, Plouzane, France, Patrick.Marchesiello@ird.fr
 

THE IMPACT OF EDDIES ON COASTAL OCEAN PRODUCTIVITY AND BIOGEOCHEMISTRY


The ocean's energy spectrum is concentrated at the mesoscale, yet the impact of mesoscale variability on ocean productivity and biogeochemistry is not well understood. Studies from the open ocean suggest an enhancing effect on productivity, but little is known elsewhere. We study here the impact of mesoscale variability on productivity, biogeochemistry and air-sea CO2 fluxes using an eddy-resolving model of the California Current System on the basis of the Regional Ocean Modeling System. We compare our standard simulation with one that is identical, except that we removed all mesoscale variations by turning off the non-linear terms in the momentum equations. This comparison reveals that eddies and other mesoscale variations tend to suppress biological productivity substantially in this coastal upwelling system, while their integrated impact on air-sea fluxes of CO2 is relatively small. We interpret this reducing effect of mesoscale variations as being driven primarily by a lateral eddy-induced transport that brings warm, nutrient depleted waters from the offshore closer to shore, thereby suppressing the effect of Ekman induced upwelling. We suspect a similar impact in other upwelling areas, whether they are coastal or open ocean.

Presented at ASLO Summer Meeting 2005, Santiago de Compostela/Spain, June 20, 2005 (Session: SS08 - Carbon and Carbonate Fluxes in the Coastal Ocean)