1. Quantifying the Mechanisms Governing Interannual Variability in Air-sea CO 2 Flux S. Doney & Ivan Lima (WHOI), K. Lindsay & N. Mahowald (NCAR), K. Moore (UCI) & Matt Maltrud (LANL) Global Ocean Hindcast Simulations (1958-2004) -Upper ocean multi-functional group, multi-nutrient ecosystem model (Moore et al., 2004) -Coupled to full-depth ocean BGC model (CCSM-POP) -Surface forcing (1957-2004) from NCEP reanalysis and satellite products -Fixed pre-industrial atmospheric CO 2 (~280 ppm) & transient anthropogenic CO 2 simulations

2. Physical & Biological Controls pCO2 = f(Temp., Salinity, DIC, Alkalinity) + ( + ) + - Net Community Prod. Winter mixed layer Circulation Light Nutrient/ DIC Supply Export Winds, Heat & Freshwater Fluxes Dust/ironCO 2 O 2 Remineralization Regenerated Prod. Biology only one factor on surface pCO 2 & air-sea CO 2 flux;

4. Ocean Model Hindcast (1957-2004)

5. Factors driving interannual pCO 2 anomalies: Wind Speed

6. Alk Temp nDIC Fresh water W. Eq. Pacific 1:1

7. Regression of surface pCO 2 anomalies on forcing terms ~1 driving term 0 minor term <0 compensating term Masked in areas of low pCO 2 ’ and low correlation Dissolved Inorganic Carbon Temperature

8. Alkalinity Freshwater Regression of surface pCO 2 anomalies on forcing terms ~1 driving term 0 minor term <0 compensating term Masked in areas of low pCO 2 ’ and low correlation

9. Q’ II A’ V’ E’ 0 100 Annual inventory change & flux anomalies X’:  I/  t = Q’ srf. flux + A’ horz. advection + E’ eddies + V’ vert. adv. + P’ net comm. prod. + other P’

10. Dust Only Physics Only

11. Dust & Physics r=0.48 SeaWiFS Physics r=0.11 Dust r=0.82 Smoothed w/ annual filter

12. Monthly Annual

13. -Models as tools for identifying ocean biogeochemical mechanisms -Regional partitioning of factors driving air-sea CO2 flux Southern Ocean wind speed variability Subtropics thermal Tropics/high latitude biology and circulation on nDIC Tropical Indo-Pacific freshwater -Non-linear interactions of dust and climate variability

16. Is low dust deposition downwind of Australia in 1997/1998 realistic? Tentative answer: yes Chen et al. precip slightly above average for 1997 and 1998 All values are anomalies from climatological mean (1979-2004): black monthly: Yellow line: 0: blue line: annual mean Two met stations close to source area: 946720 and 944820 have fewer dust events than average in 1997 and 1998 Low dep due to low source Low dep due to high precip Model Obs

17. Dust & Physics r=0.60 SeaWiFS Physics r=0.56 Dust r=0.71 Monthly anomalies