CO 2 MEASUREMENTS ON THE PIRATA NETWORK Nathalie Lefèvre, IRD LOCEAN Antoine Guillot, DT INSU Brest Laurence Beaumont, Théo Danguy, DT INSU [email protected].

CO2 MEASUREMENTS ON THE PIRATA

NETWORK

Nathalie Lefèvre, IRD LOCEAN

Antoine Guillot, DT INSU Brest

Laurence Beaumont, Théo Danguy, DT INSU

[email protected]

CARBOOCEAN, annual meeting, Gran Canaria, 4-8 December 2006

Scientific objectives

European project CARBOOCEAN (theme 1, WP4)

Estimate the flux of CO2 at the air-sea interface by

developing an observational network for CO2

Network for the tropical Atlantic:

2 merchant ships (France-Brazil, red line, France-

French Guiana, green line) equipped with an

automated CO2 system to measure atmospheric

and oceanic CO2 underway by infrared detection.

2 CO2 sensors for PIRATA moorings at 6oS,

10oW and 8oN, 38oW (black dots) using a

colorimetric method (CARIOCA buoy technology).EGEE 3 cruise (in blue)

See poster

Choice of the PIRATA moorings for installing CO2 sensors

SeaWiFs, Septembre 2003Impact of the Amazon outflow on the

CO2 distribution during the retroflection

of the North Brazil Current (NBC)

Advection far East in the North

Equatorial Counter-Current (NECC)

CO2 sensors on PIRATA moorings:

6oS, 10oW: CO2 time-series in the SEC

8oN, 38oW: CO2 time-series in the NECC

10W40W

10S

Installation of the first CO2 sensor on the PIRATA

mooring at 6oS, 10oW during the EGEE 3 cruise (June 2006)

Box with electronics

Argos antenna

CO2 sensor and oxygen optode

CO2 sensors built at DT INSU (Antoine Guillot, Théo Danguy, Laurence Beaumont)

Comparison IR-CARIOCA

27

27.05

27.1

27.15

27.2

27.25

27.3

27.35

27.4

27.45

27.5

158.2 158.3 158.4 158.5 158.6

Day

SS

T

376

377

378

379

380

381

382

383

384

385

386

fCO

2 (m

atm

)

SSTSST IRfCO2fCO2 IR

Data of the CO2 sensor since the 7th of June 2006

SST decrease due to the upwelling (June-September) CO2 increase

Hourly

measurements

of CO2, SST

and O2 sent by

ARGOS

fCO2 = -19.54 * SST + 895.84 r2 = -0.88

Correlation between fCO2 and SST and SSS

Detrended and normalized hourly fCO2, sea surface temperature and sea surface

salinity (interpolated from PIRATA daily records) as a function of time (in days).

Data from 8 June to 7 October 2006.

Colder and fresher seawater associated with higher CO2 concentrations

Oxygen measurements using the Aanderaa optode

Optode3835

Pipe connection(20 cm)

Too large amplitude for O2 diurnal cycle (~20 mmol/ kg) after 3 months

Diurnal cycle consistent with biological activity

Dissolved inorganic carbon (DIC)

calculated using TA=f(S) and fCO2

Decrease of DIC during the day

(photosynthesis)

Increase of DIC during the night

(convection & respiration)

14-21 Sep. 2006

DIC and fCO2 variability after the upwelling

season

Example for 17-23 November 2006

2063

2063.5

2064

2064.5

2065

2065.5

2066

2066.5

2067

2067.5

2068

321 322 323 324 325 326 327 328

Time (days)

DIC

24.5

24.6

24.7

24.8

24.9

25

25.1

SS

T

DICSST

424

426

428

430

432

434

436

438

440

442

321 322 323 324 325 326 327 328

Time (days)fC

O2

24.5

24.6

24.7

24.8

24.9

25

25.1

fCO2SST

Diurnal cycle detected on both DIC and fCO2

Conclusions

Very encouraging results: CO2 data since June

Source of CO2 from 1.19 (June) to 6.82 m.mol.m-2.d-1 (September)

fCO2

SST

Plan for 2007

CO2 sensor to be installed at 8oN, 38oW during the PIRATA

Brazil cruise in 2007

Replace the sensor (lifetime of 1 year) during EGEE 5 (June

2007) to continue the time-series (the existing one is sent for

calibration, and for renewal of the dye at the DT INSU while a

spare one is installed).