COLLABORATORS: P. Estrade, S. Herbette, C. Lett, A. Peliz, C. Roy, B. Sow, C. Roy EDDY-DRIVEN DISPERSION IN COASTAL UPWELLING SYSTEMS California Canary.
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Presentation on theme: "COLLABORATORS: P. Estrade, S. Herbette, C. Lett, A. Peliz, C. Roy, B. Sow, C. Roy EDDY-DRIVEN DISPERSION IN COASTAL UPWELLING SYSTEMS California Canary."— Presentation transcript:
COLLABORATORS: P. Estrade, S. Herbette, C. Lett, A. Peliz, C. Roy, B. Sow, C. Roy EDDY-DRIVEN DISPERSION IN COASTAL UPWELLING SYSTEMS California Canary Benguela Humbolt Patrick Marchesiello ROMS Meeting, VENEZIA October 19 2004
APPLICATION TO THE CALIFORNIA CURRENT SYSTEM: CONFIGURATION AND STRATEGY 20km, 10km, 5km 20km, 10km, 5km, 2.5km Volume Averaged KE (cm 2 /s 2 ) Surface Averaged KE (cm 2 /s 2 ) Nesting of the inner domain: on-line or off-line. Model integration: 10 years. Surface and lateral boundary forcing: Monthly climatologies.
Mesoscale Variability in the CCS n Realistic simulation of the Coastal Transition Zone n More than 2/3 of the mesoscale variability is intrinsic, and produced through instabilities (baroclinic and barotropic) of the coastal currents generated in the upwelling process. SST - AVHRRSST - Model Marchesiello et al. (JPO, 2003)
Drifter Estimation  Model 110 Resolution [km] 520 10 100 Eddy Kinetic Energy [cm 2 /s 2 ] Model Convergence
The upwelling front results from upwelling of the thermocline (Mooers et al., 1976) Baroclinic instability: energy conversion from available potential energy to eddy kinetic energy varies with vertical shear of velocity (Pedlosky, 1986; Barth, 1989) U=(g’H 0 ) 1/2 where g’=g(ρ2-ρ1)/ ρ2 BAROCLINICITY: Two layer approach
California g’=0.019 Canary g’=0.008 Temperature relative to surface Salinity relative to surface Canary California Canary Salinity profiles & Reduced Gravity Potential density JOINT I cruise, after Huyer(1976)
T’u’ = -Kx dT/dx 100km T Offshore distance 500km Mixing X 100 m 2 /s Swenson and Niiler (1996) from drifting-buoy trajectories, 1985-1988: K = 1.1 - 4.6 10 3 m 2 /s with higher values for Kx compared to Ky Model: Kx = 2.3 10 3 m 2 /s and Ky = 1.3 10 3 m 2 /s MESOSCALE CROSS-SHORE DIFFUSION Erosion of coastal properties
Nitrate Chlorophyll A UpwellingNitrification New Prod. Excretion Breakdown Grazing Aggregation Mortality Light Sink Zooplankton PhytoplanktonLarge Detritus HYDRODYNAMICS Transport Small Detritus Ammonium Reg. Prod. THE ECOSYSTEM MODEL
LINEAR MODEL (advection terms turned off in the momentum equation) New Production NO3 transport NON-LINEAR MODEL Spring-time biology fluxes Units: mmol N cm -2 a -1
Retention Map From Lagrangian Study SSH Standard Deviation Seawifs Annual Chl
BIOLOGICALLY ACTIVE AREA IN UPWELLING SYSTEMS What drives the observed differences in cross- shore distribution of physical and biogeochemical properties? Latitude (solar flux) Fe depositions from Sahara (Lene et al., 2001) Shelf width & nutrients (Johnson et al., 1997) Mesoscale physics (Marchesiello et al., 2003) PERU-CHILI CALIFORNIA CANARY BENGUELA