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Phytoplankton C:Chl difference between tropical Pacific & Atlantic: Implications for C estimates Wendy Wang Univers

Phytoplankton C:Chl difference between tropical Pacific & Atlantic: Implications for C estimates Wendy Wang University of Maryland/ESSIC. Collaborators: Ragu Murtugudde: ESSIC/UMD Robert Le Borgne: IRD, New Caledonia Mike Behrenfeld: Oregon State University

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Phytoplankton C:Chl difference between tropical Pacific & Atlantic: Implications for C estimates Wendy Wang Univers

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  1. Phytoplankton C:Chl difference between tropical Pacific & Atlantic: Implications for C estimates Wendy WangUniversity of Maryland/ESSIC Collaborators: Ragu Murtugudde: ESSIC/UMDRobert Le Borgne: IRD, New Caledonia Mike Behrenfeld: Oregon State University Emmanuel Boss: University of Maine Susan Brown: SOEST/Hawaii Uni. Emilio Maranon: University of Vigo, Spain

  2. Outline • Motivation/Scientific Question • Modeling Approach • Results & Conclusion • Future Work

  3. Surface chlorophyll from SeaWiFS • Pacific: 0.1-0.3 • Atlantic: 0.1-0.5

  4. A big question: Is carbon biomass lower in tropical Pacific than Atlantic? Basin-scale C:Chl ratio!!

  5. Basin-scale Modeling • Model derivation & cal/val in Pacific • Model application & cal/val in Atlantic • Comparison of C:Chl & carbon biomass between Pacific and Atlantic

  6. A fully coupled basin-scale model OGCM: Gent & Cane (1989) Murtugudde et al.(1996) Ecosystem model: Christian et al.(2001) Wang et al. (2006a) Wang et al. (2008) C chemistry model: Wang et al. (2006b) Phyto. dynamic model: Wang et al.(2009) Atm. Forcing/ SAM (PAR) (AT, WS, SR, P) (WS) PDM (C:Chl) (t) DMEC OGCM (N) (u, v, t, s)

  7. Dynamic Ecosystem-Carbon Model Chlorophyll

  8. C:Chl vs. depth (data from Le Bouteiller et al., 2003) 0° η0 3°S • Linear decrease in EZ • Similar value at ED • C:Chl (<3μm): • 0°: ~140 • 3°S: ~220 , , , ηMIN (<3μm)

  9. Parameterization of vertical C:Chl (η)(Wang et al., 2009) (ZE: euphotic depth) , , ,

  10. Surface C:Chl vs. growth rate (μ0*)(Le Bouteiller et al., 2003) Community • Non-light limitation: • η0 linearly decrease with μ0* • C:Chl ratio: • higher in small cell than large cell , , , Small cells (<3μm)

  11. Parameterization of surface C:Chl (Wang et al., 2009) , , , , ,

  12. Model (Wang et al., 2009) Data (180°, Oct-Nov, 96)(Brown et al. 2003)

  13. Model & data agree: • C: highest at 0° • DCM: depth & Chl conc. • C:Chl: 80-140 (surface) • ~40 at 100 m

  14. Dataset for model cal/val in Pacific

  15. Data distribution in eq. Pacific 1996 2005 2006 2007 1994/96

  16. Model Data DCM depth: ~100m in WP ~50m in CEP Chl. in WP ML: <0.1 Chl. at DCM: 0.2-0.3

  17. SeaWiFS, model, in situChl

  18. Surface Chl: model vs. SeaWiFS

  19. Interannual variation (5°N-5°S)

  20. Model skills , , , • R: 03-0.7 • NSD: 1-1.5 • Z. R > M. R • Spat/Temp: • R>0.7 • NSD=1

  21. Summary (eq. Pacific) • PDM reproduces zonal DCM: ~100 m in WP ~50 m in C/EEP • Spatial & temporal variations: Interannual: model & data agree well HNLC frontal features

  22. AMT 1-12 (1995-2000): • Bio-optical • Phytoplankton • Zooplankton • AMT-3: • (Sep-Oct, 96) • Chlorophyll • Carbon • Nitrate • PP

  23. Model vs. data • Surface chl: • The same (0.1-0.2) • DCM chl: • Model > data • DCM depth: • The same (50-150m)

  24. Model vs. data • Surface C: • Similar (8-16) • DBM C: • ? • DBM depth: • Similar?

  25. Model vs. data (1997-2007) surface Chl in Atlantic Open ocean:similar magnitude & spatial pattern

  26. Summary (eq. Atlantic) • PDM reproduces meridional DCM: South: >120 m North: ~50 m • Surface C & Chl: Model & data agree well

  27. Pacific vs. Atlantic , , ,

  28. Surface averages (model/data)

  29. Conclusion • Chl: Pacific < Atlantic • C:Chl ratio: Pacific > Atlantic • Carbon: Pacific ≥ Atlantic

  30. Future work • What about primary production? • C:Chl ratio: Pacific > Atlantic • Growth rate: Pacific < Atlantic • PP: ??? • Temporal variability? • Pacific: interannual > seasonal • Atlantic: ???

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