1. 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 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.  Pacific: 0.1-0.3 Surface chlorophyll from SeaWiFS  Atlantic: 0.1-0.5

4. Is carbon biomass lower in tropical Pacific than Atlantic? A big question: 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 OGCM DMEC PDM (u, v, t, s) (AT, WS, SR, P) (PAR) (t) (WS) (N) (C:Chl)

7. Dynamic Ecosystem-Carbon Model Chlorophyll

8. C:Chl vs. depth ( data from Le Bouteiller et al., 2003 ),,, Linear decrease in EZ Similar value at ED C:Chl (<3μm): 0°: ~140 3°S: ~220 (<3μm) 0°0°3°S η0η0 η MIN

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

10. Surface C:Chl vs. growth rate (μ 0 *) (Le Bouteiller et al., 2003),,, Non-light limitation: η 0 linearly decrease with μ 0 * C:Chl ratio: higher in small cell than large cell Community 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 DatasetLongLatTime FLUPACChl166E-150W0Oct 94 ZonalFluxChl166E-150W0May 96 EBENEC:Chl1808N-8SOct 96 Box Project Chl140W, 125W8N-8SSep 05 Aug 06 May 07 SeaWiFSChl150E-90W15N-15S97-07

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

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

17. SeaWiFS, model, in situ Chl

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. Band (10N-10S) Pacific (160E-90W) Atlantic (40W-0) Chl (mg/m3)0.15/0.150.17/0.2 C:Chl12075 Carbon (mg C/m3) 1815 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: ???