aprcolacmar
TRANSCRIPT
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Variability of the parameters of the CO2 system in the continental shelf of Ceará
Andréa Carvalho, Nathalie Lefèvre, Rozane Marins, Roseline Torres
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The global carbon budget
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Climatology of Takahashi et al., 2009
Sources and Sinks
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Processes affecting CO2 in the ocean
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
www.pmel.noaa.gov
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• Impact of rivers (Amazon): large blooms of
diatoms create CO2 drawdownsATM
SOURCE OF CO2
SINK OF CO2
Lefèvre et al., 2010
The coastal ocean: a source or a sink for atmospheric CO2?
Jaguaribe River
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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.
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The Cruise
Measurements:•Physical Parameters (CTD, Thermosal)•CO2 parameters (TCO2,TA,pCO2)•Chlorophyll a•Dissolved Oxygen
BRAZIL
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Spatial Distribution of pCO2
SST= 26.73 ±0.14 SSS= 36.46± 0.21
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TCO2 and TA
TCO2= 2059.2 ±4.6 µmol.Kg-1 TA= 2397.7 ±5.3 µmol.Kg-1
2380.0 2385.0 2390.0 2395.0 2400.0 2405.0 2410.0 2415.02030.0
2035.0
2040.0
2045.0
2050.0
2055.0
2060.0
2065.0
2070.0
2075.0
TA
TCO2
36 36.2 36.4 36.6 36.8 372380
2390
2400
2410
2420
2430
2440
2450TA=f(S)
C...
Salinity
TA
y = 0,6341x + 538,9R² = 0,5685
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Chlorophyll a
Method of Jeffrey and Humphrey (1975)Mean Chlorophyll= 0.09 ± 0.09µg.L-
1
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Dissolved Oxygen
•Winkler 1888
Mean DO = 6.5 ± 0.15 mg.L-1
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Air – sea flux of CO2
Measurements:
Mean fCO2 sea= 401.6±8.6 µatm
Mean fCO2 air= 375.8 µatm
F = k(wind).Ko.(T, S).(fCO2 sea – fCO2 air)
F > 0 SOURCE
F < 0 SINK
k= 0.27 wsp2 (Sc/660)-0.5
Ko = Solubility of CO2 (Weiss, 1974)
Mean Flux of CO2 to the atmosphere= 3.53 ±1.15 mmol.m-
2.day-1
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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).
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Acknowledgements
• 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.
Special thanks
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ANEXOS
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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 acidificationKnowing 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)
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• 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.
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DICx TA
36 36.2 36.4 36.6 36.8 372380
2390
2400
2410
2420
2430
2440
2450TA=f(S)
Core...
Salinity
TA
2380.0 2385.0 2390.0 2395.0 2400.0 2405.0 2410.0 2415.02030.0
2035.0
2040.0
2045.0
2050.0
2055.0
2060.0
2065.0
2070.0
2075.0
TA
DIC
SSS x TA
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The CO2 System
CO2 standards (air with known CO2 concentration:280 ppm, 360 ppm, 500 ppm)
Successive measurements:
• CO2 standards
• Seawater• Atm air• Repeat cycle: standards…
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•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 .
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Building of a CO2 system in Brazil ongoing at INPE
French system on board the Corenav 3, Oct. 2012
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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.
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•DIC
•TA
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DIC
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TA