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Global trends in air-sea CO 2 fluxes based on in situ and satellite products Rik Wanninkhof, NOAA/AOML ACE Ocean Productivity and Carbon Cycle (OPCC) Workshop.

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Presentation on theme: "Global trends in air-sea CO 2 fluxes based on in situ and satellite products Rik Wanninkhof, NOAA/AOML ACE Ocean Productivity and Carbon Cycle (OPCC) Workshop."— Presentation transcript:

1 Global trends in air-sea CO 2 fluxes based on in situ and satellite products Rik Wanninkhof, NOAA/AOML ACE Ocean Productivity and Carbon Cycle (OPCC) Workshop - June 6-8,UC Santa Barbara

2 Sea surface temperature (SST) Wind speed CCMP (Cross-Calibrated Multi-Platform wind product) [Atlas et al., 2011] Sea-air CO 2 Flux = K 0 × k × Δ pCO 2 [Takahashi et al., 2009] OPCC OPCC Global Ocean Sea-Air CO 2 Fluxes Methods: ΔpCO 2 climatology k 660 = 0.251

3 Wind k  pCO 2 Air-Sea CO 2 Flux SST Transport Biology Wind Waves Bubbles Surface Film Near Surface Turbulence Bock et al. (1999) OPCC OPCC Global Ocean Sea-Air CO 2 Fluxes Factors influencing CO 2 flux estimates

4 OPCC OPCC Global Ocean Sea-Air CO 2 Fluxes Data coverage T-09 climatology

5 A Multi-national Effort: England USA France Netherlands Germany Spain China Japan Tasmania Norway And more… Complete Data Set: 1968– M points Our contribution: 3M points OPCC OPCC Global Ocean Sea-Air CO 2 Fluxes Surface Ocean Carbon Atlas (SOCAT)

6 OPCC OPCC Global Ocean Sea-Air CO 2 Fluxes Remote sensing Wind: CCMP 6-hr ¼˚ k 660 = based on global 14 C constraint Gas transfer velocity

7 OPCC Global Ocean Sea-Air CO 2 Fluxes Global 14 C constraint Broecker and Peng (1994) Transfer velocity k av = 17.5 cm/hr u 2 = 69.3 (m/s) 2 u mean ≈ 7.4 m/s Semi-infinite Half space Bomb 14 C inventory constraint Globally: a = Constant

8 OPCC Global Ocean Sea-Air CO 2 Fluxes Relationship of k and U 10 Good agreement with global bomb 14 C constraint and local studies Ho et al. 2011

9 Uncertainty in different components of the flux estimate (adapted from section 6, T- 09) Takahashi et al. (2009)RECCAP (2011) Pg C yr -1 %Pg C yr- 1 %Pg C yr- 1 Net flux ∆pCO 2 ±0.18 ±13%±0.18 k ±0.42 ± 30%±0.2 Wind (U)±0.28 ± 20%±0.2 a ±0.5 ± 35%±0.5 Total±0.7 ± 53%. ±0.6 Under-sampling bias Pre-industrial sea-air flux 0.4 ± ± 0.2 Anthropogenic CO 2 flux-2.0 ± ± 0.8 OPPC OPPC Sea-Air CO 2 Fluxes Climatological Magnitude and Uncertainty

10 Temperature (C)-2 –30 (  ln pCO 2 /  T) = o C % VariableRangeRelationEffect TCO 2 (  mol kg -1 ) (  ln pCO 2 /  Tln TCO 2 ) = % Alkalinity(  mol kg -1 )* (  ln pCO 2 /  Tln TALK) = % Salinity(  mol kg -1 )* (  ln pCO 2 /  Tln S) = 0.94 ~10% *Alkalinity and salinity are proportional and can be accounted for OPCC Global Ocean Sea-Air CO 2 Fluxes Factors influencing surface water pCO 2

11 Annual uptake of anthropogenic CO 2 since 1960 from models. The absolute uptake (solid line, left axis) has increased over time while the fraction of uptake (=ocean uptake/fossil fuel CO 2 release *100) (dashed line, right axis) has decreased. Data are obtained from (Le Quéré et al., 2009). OPPC OPPC Sea-Air CO 2 Fluxes: Model and atm. based estimates of trends

12 OPCC OPCC Sea-Air CO 2 : Flux variability Trends F ym = k ym K 0 ym {[ΔpCO m + (δpCO 2SW / δSST) 2000m × ΔSST ym – 2000m ] }, (δpCO 2SW / δSST) 2000m : Optimal subannual relationships for each 4˚ by 5˚ grid box Park et al. Tellus B 2010:Variability of global net sea-air CO 2 fluxes over the last three decades using empirical relationships

13 The linear regressions (solid line) for the flux are 0.009± Pg C yr -1, respectively. The 20-years mean values for the flux is -1.12± 0.13 Pg C, respectively. Decrease in uptake due to winds and SST feedbacks OPCC OPCC Sea-Air CO 2 Fluxes Trends Sea-air CO 2 Flux = K 0 × k × Δ pCO 2

14 OPCC OPCC Global Ocean Sea-Air CO 2 Fluxes Remote sensing How can we quantify the impact of [remotely measured] biological processes on ∆pCO 2 ?  Regional approach  Multi-sensor  Melding in situ and remotely sensed information

15 Annual uptake of anthropogenic CO 2 since 1960 from models. The absolute uptake (solid line, left axis) has increased over time while the fraction of uptake (=ocean uptake/fossil fuel CO 2 release *100) (dashed line, right axis) has decreased. Data are obtained from (Le Quéré et al., 2009). OPCC OPCC Sea-Air CO 2 Fluxes: IPCC estimates

16 Figure 4. Zonal wind comparison of several global wind products for the year The differences of up to 2 m/s are observed but the biases are not always consistent between high and low latitudes. (Figure courtesy of C. Sweeney).CCMP = Cross Calibrated Multi- Platform winds (Atlas et al., 2011); ECWMF =European Center for Medium Weather Forecasting; NCEP = National Center for Environmental Prediction; QSCAT = QuikSCAT polar orbiting satellite with an 1800 km wide measurement swath on the earth's surface equipped with the microwave scatterometer SeaWinds OPCC OPCC Sea-Air CO 2 : Global Winds


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