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Published byKevin Watts Modified over 9 years ago
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On the role of eddies for coastal productivity and carbon cycling Hartmut Frenzel 1, Nicolas Gruber 2,1, Gian-Kasper Plattner 2, Takeyoshi Nagai 3,1, James C. McWilliams 1, Zouhair Lachkar 2 1 IGPP & DAOS, UCLA 2 Institute of Biogeochemistry and Pollutant Dynamics, ETH Zürich, Switzerland 3 Tokyo Institute of Fisheries, Japan
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(gC m -2 yr -1 )
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Horizontal resolution: 5 km Vertical resolution: 20 levels climatological forcing WOA01 for T,S; COADS for winds NPZD model Nitrogen based (no iron limitation) Upwelling system focused Fixed stoichiometric ratios of C:N US WEST COAST CONFIGURATION OF ROMS [Gruber et al., DSR I, 2006]
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USWC-5km ROMS
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IMPACT OF MESO-SCALE PROCESSES Standard (eddy) run: #define UV_ADV Linear run: #undef UV_ADV (VISC2 = 100 m 2 /s) Both for USWC 5 km configuration
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(all fluxes: mol C m -2 yr -1 )
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Eddy induced anomalous circulation
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California upwelling: highest TKE and lowest PP
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NPP: California vs. Canary Current System [Gruber et al., in prep. 2007 ]
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UWI: California vs. Canary Current System [Gruber et al., in prep. 2007]
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EKE: California vs. Canary Current System [Gruber et al., in prep. 2007]
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[Gruber et al., in prep. 2007]
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NPP/UWI and NPP/EKE: California and Canary CS [Gruber et al., in prep. 2007]
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SUMMARY Meso- and submesoscale processes tend to suppress primary production and air-sea fluxes of CO 2 in coastal upwelling systems. This is due to an eddy-induced "overturning" circulation that counteracts the upwelling and leads to a “leakage” of nutrients out of the upwelling region. First results indicate that the differing levels of eddy kinetic energy in the various upwelling systems are a primary reason for their large differences in primary production.
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Eddy-partNon-eddy part EDDY CONTRIBUTION TO OFFSHORE TRANSPORT Nagai et al. (in prep. 2007) Offshore distance Total offshore transport of NO 3 & NH 4 Eddy-tracking Fraction by Eddies >60% of offshore transport by eddies
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MECHANISMS OF OFFSHORE TRANSPORT Filament transport Subduction Westward propagating eddies Upwelling Nearshore ~200km Beyond 200 km
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Acknowledgments Funding: NASA and NSF Computer time: NCSA
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