eddy-driven dispersion in coastal upwelling systems
DESCRIPTION
EDDY-DRIVEN DISPERSION IN COASTAL UPWELLING SYSTEMS. Patrick Marchesiello. COLLABORATORS: P. Estrade, S. Herbette, C. Lett, A. Peliz, C. Roy, B. Sow, C. Roy. ROMS Meeting, VENEZIA October 19 2004. California. Canary. Benguela. Humbolt. Coastal Upwelling?. - PowerPoint PPT PresentationTRANSCRIPT
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COLLABORATORS: P. Estrade, S. Herbette, C. Lett, A. Peliz, C. Roy, B. Sow, C. Roy
EDDY-DRIVEN DISPERSION IN COASTAL UPWELLING SYSTEMS
EDDY-DRIVEN DISPERSION IN COASTAL UPWELLING SYSTEMS
CaliforniaCanary
BenguelaHumbolt
Patrick Marchesiello
ROMS Meeting, VENEZIA
October 19 2004
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Coastal Upwelling?
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California Senegal
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Divergencezone
Retentionzone
Eddy mixing zone
Coastal upwelling
Mitchum & Clark, 1978Lentz & Austin, 2002
Marchesiello et al., 2003
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ROMS_AGRIF
• ROMS: HYDRODYNAMIC MODEL optimized for regional
and coastal high resolution, multi-scale, multidisciplinary
applications
• AGRIF: Online, synchronous nesting method (L. Debreu)
• ROMS_TOOL: Pre- and post-processing package (P.
Penven)
• DIAGNOSTIC TOOLS: Lagrangian tracers, budgets …
• APPLICATION MODELS: Ecosystem dynamics, Water
quality, Sediment transport
http://www.ird.brest.fr/Roms_tools
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POG - 0.25 deg ROMS – 0.25 deg
Note on Regional Models
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CALIFORNIA
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APPLICATION TO THE CALIFORNIA CURRENT SYSTEM: CONFIGURATION AND STRATEGY
APPLICATION TO THE CALIFORNIA CURRENT SYSTEM: CONFIGURATION AND STRATEGY
20km, 10km, 5km
20km, 10km, 5km, 2.5km
Volume Averaged KE (cm2/s2)
Surface Averaged KE (cm2/s2)
Nesting of the inner domain: on-line or off-line. Model integration: 10 years. Surface and lateral boundary forcing: Monthly climatologies.
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Mesoscale Variability in the CCS
Mesoscale Variability in the CCS
Realistic simulation of the Coastal Transition Zone 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)
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Drifter Estimation [180]
Model
1 10
Resolution [km]
5 20
10
100
Ed
dy K
inet i
c E
nerg
y [
cm
2/s
2]
Model Convergence
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CANARY - COMPARISON
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Canary Current System Configuration
ROMS – Canary 25 km
C. Vert
C. BlancC. Blanc
ROMS – Sahara 5 km
Mercator
Levitus
Clipper
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SaharaCalifornia
8 20 17 26
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Mesoscale ActivityIn California and Canary Systems
Model
SSH Standard Deviation
[cm]
For non-seasonal
variability
California
Sahara
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Mesoscale ActivityIn California and Canary Systems
Model
SSH Standard Deviation
[cm]
For non-seasonal
variability
California
Sahara
AltimetryTopex/ERS from AVISO
California
Sahara
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Wind Forcing
California Morocco
Units: Pascal
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• 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’H0)1/2
where g’=g(ρ2-ρ1)/ ρ2
BAROCLINICITY: Two layer approach
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•California g’=0.019
•Canary g’=0.008
Temperature relative to surface
Salinity relative to surface
Canary
California
California
Canary
Salinity profiles & Reduced Gravity
Potential density
JOINT I cruise, after Huyer(1976)
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IMPACT
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T’u’ = -Kx dT/dx
100km
T
Offshore distance500km
Mixing
X 100 m2/s
Swenson and Niiler (1996) from drifting-buoy trajectories, 1985-1988: K = 1.1 - 4.6 103 m2/s with higher values for Kx compared to Ky
Model: Kx = 2.3 103 m2/s and Ky = 1.3 103 m2/s
MESOSCALE CROSS-SHORE DIFFUSION
Erosion of coastal properties
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Nitrate
Chlorophyll A
Upwelling Nitrification
New
Pro
d.
Excre
tion
Bre
akd
ow
n
Grazing
Aggregation
Mortality
Light
Sink
Zooplankton Phytoplankton
Large Detritus
HYDRODYNAMICS
Transport
Small Detritus
Ammonium
Reg. Prod.
THE ECOSYSTEM MODEL
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LINEAR MODEL
(advection terms turned offin the momentum equation)
New Production NO3 transport
NON-LINEAR MODEL
Spring-time biology fluxesUnits: mmol N cm-2 a-1
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Retention MapFrom Lagrangian Study
SSHStandard Deviation
Seawifs Annual Chl
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BIOLOGICALLY ACTIVE AREA IN UPWELLING SYSTEMS BIOLOGICALLY ACTIVE AREA IN UPWELLING SYSTEMS
0
100
200
300
400
500
Californie Humbold Canaries Benguela
Biologically Active Area (1000 km2)
SeaWIFS estimations by M. Carr (2002) 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-CHILICALIFORNIA CANARY BENGUELA
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