Variability of the parameters of the CO2 system in the continental shelf of Ceará Andréa Carvalho, Nathalie Lefèvre, Rozane Marins, Roseline Torres The global carbon budget Sources and Sinks Climatology of Takahashi et al., 2009 Processes affecting CO2 in the ocean www.pmel.noaa.gov Processes Impact on fCO2 Warming Increase of 4%/oC (thermodynamical relationship) Increase of salinity Increase of fCO2 Chlorophyll production Decrease of fCO2 (photosynthesis) Upwelling Increase of surface fCO2 The coastal ocean: a source or a sink for atmospheric CO2? • Impact of rivers (Amazon): large blooms of diatoms create CO2 drawdowns SOURCE OF CO2 ATM SINK OF CO2 Lefèvre et al., 2010 Jaguaribe River Objectives • Generate the first field measurements of the CO2 parameters for the region; • Describe the surface distribution of the carbon properties; • Understand the processes (physical/biological) that influcence the CO2 distribution in the sea surface and; • Determine the air-sea flux of CO2 during the dry season. The Cruise BRAZIL Measurements: •Physical Parameters (CTD, Thermosal) •CO2 parameters (TCO2,TA,pCO2) •Chlorophyll a •Dissolved Oxygen Spatial Distribution of pCO2 SST= 26.73 ±0.14 SSS= 36.46± 0.21 TCO2 and TA TA= 2397.7 ±5.3 µmol.Kg-1 TCO2= 2059.2 ±4.6 µmol.Kg-1 2075,0 TA=f(S) 2450 2070,0 Core… 2440 2065,0 2420 2055,0 TA TCO2 2430 2060,0 2410 2050,0 2400 y = 0,6341x + 538,9 R² = 0,5685 2045,0 2040,0 2380,0 2390,0 2400,0 TA 2410,0 2390 2380 36 36,2 36,4 36,6 Salinity 36,8 37 Chlorophyll a Method of Jeffrey and Humphrey (1975) Mean Chlorophyll= 0.09 ± 0.09µg.L-1 Dissolved Oxygen • Winkler 1888 Mean DO = 6.5 ± 0.15 mg.L-1 Air – sea flux of CO2 F = k(wind).Ko.(T, S).(fCO2 sea – fCO2 air) F > 0 SOURCE k= 0.27 wsp2 (Sc/660)-0.5 F < 0 SINK Ko = Solubility of CO2 (Weiss, 1974) Measurements: Mean fCO2 sea= 401.6±8.6 µatm Mean fCO2 air= 375.8 µatm Mean Flux of CO2 to the atmosphere= 3.53 ±1.15 mmol.m-2.day-1 Conclusions • Predominance of physical processes over biological processes; • A source of CO2 to the atmosphere in October 2012; • Mean Flux CO2= 3.53 ±1.15 mmol.m-2.day-1 and; • No riverine influence observed during this season. And Perspectives Determine the seasonal variability (measurements during the wet season). Special thanks • ECMWF ERA-Interim wind data from the ECMWF data server • The service national SNAPO-CO2 (LOCEAN, Paris) for the analyses of dissolved inorganic carbon and total alkalinity. Acknowledgements ANEXOS Parameters of the CO2 system 4 parameters: fCO2, DIC, TA and pH pCO2 and fCO2 : non ideal gas DIC = [CO2]* + [CO32-] + [HCO3-] µmol kg-1 TA: bicarbonate (HCO3-) and carbonate (CO3--) µmol. Kg-1 pH: monitoring acidification Knowing 2 parameters we can calculate the other two: pH TA DIC fCO2 pH, TA - - ± 3.8 ± 2.1 pH, DIC - ± 2.7 - ± 1.8 TA, DIC ± 0.0062 - - ± 5.8 TA, fCO2 ± 0.0021 - ± 3.4 - DIC, fCO2 ± 0.0023 ± 3.0 - - fCO2, pH - ± 18 ± 15 - Errors made on the calculation of the carbon parameters from the measurements of two of them (Millero, 1995; Zeebe and Wolf-Gladrow,2007) • Seawater samples were taken for surface analysis chlorophyll a according to Jefrey and Humphey 1970 • inorganic carbon (TCO2) and total alkalinity (TA) using potenctiometric titration derived from the method developed by Edmond (Edmond, 1970) with a closed cell. 2075,0 2070,0 2065,0 DIC DICx TA 2060,0 2055,0 2050,0 2045,0 2040,0 2380,0 2385,0 2390,0 2395,0 TA 2400,0 2405,0 TA=f(S) 2450 Corenav 3 2440 2430 SSS x TA TA 2420 2410 2400 2390 2380 36 36,2 36,4 36,6 Salinity 36,8 37 2410,0 The CO2 System Successive measurements: • CO2 standards • Seawater • Atm air • Repeat cycle: standards… CO2 standards (air with known CO2 concentration: 280 ppm, 360 ppm, 500 ppm) • The partial pressures of CO2 (pCO2 ) for the ocean and atmosphere were measured underway during the cruise by an infrared CO2/H2O detector Li-Cor model 7000 as described by Dickson et al. 2007 . French system on board the Corenav 3, Oct. 2012 Building of a CO2 system in Brazil ongoing at INPE Air sea flux • The net sea-air CO2 fluxes (F, mmol m-2 d-1) is calculated using : F= k K0 (fCO2sw- fCO2air) • K0 is the solubility of CO2 as a function of SST and SSS (Weiss, 1974). The gas transfer velocity for CO2(k) was calculated according to Sweeney et al. (2007): k=0.27 wsp2(Sc/660)-0.5 . • Sc is the Schmidt number and 660 is the Schmidt number of CO2 in seawater at 20°C (Wanninkhof, 1992) and wsp is the Wind speed at 10m. • DIC • TA DIC TA