Variability of fCO2 in the tropical

and North Atlantic Ocean

Nathalie Lefèvre, Denis Diverrès, Francis Gallois

VOS lines in CARBOOCEAN

14 voyages MN Colibri February 2006 to March 200911 voyages Monte Olivia July 2008 to March 2009

NATR

NAST(E)

WTRA

ETRA

NAST(E): North Atlantic Subtropical Gyre (East) Westerlies domain

NATR: North Atlantic Tropical Gyre trade winds domain

WTRA: Western Tropical Atlantictrade winds domain

ETRA: Eastern Tropical Atlantic

SATL: South Atlantic

Biogeochemical provinces sampled by the two VOS lines

CNRY: Canary Current Coastal

NAST(W)

SATLBrazil Current

February cruises

N. Atl. subtropical and tropical gyres

NATR

NAST(E)

Atmosphere

WTRA

• Sink in NAST(E)

• Influence of

upwelling in NATR

July and August cruises

N. Atl. subtropical and tropical gyres

Atmosphere

NATR

NAST(E)

NATR

NAST(E)

WTRA

• Source in NAST(E)

• Source in NATR

Western tropical Atlantic (Monte Olivia track)

NATR North-South gradient

>2oN undersaturation (NECC)

< 2oN sursaturation (SEC)

NECCSEC

WTRASATL

NAST(E)

Cither February 1993, 7o30’N

PLUMAND October 2007, 7o30’N

Transit NECC August 2008, 7oN

February 2006, legs 1 & 2April 2007June 2007July 2008August 2007

WTRA: the NECC region

TA = 58.066 S + 264.914 r2 = 0.997

DIC = 50.59 S + 189.42 r2 = 0.988

Western tropical Atlantic (60oW-30oW, 0o-12oN)

fCO2 = 15.66 ( 0.097) S – 161.175 ( 3.039) for S < 35r2 = 0.92

Strong salinity control in the WTRA

Ternon et al., 2000: 11.72 (0.06) atm/ psu Körtzinger, 2003: 13.18 ( 0.06) atm/ psu

r.TAr + s.TAs = TAobs

r + s = 1

Assumption of conservative mixing of TA

Amazon endmember (S=0): TAr = 265 mol/ kg

Ocean endmember (S=34.7): TAs = 2277 mol/ kg

Eastward propagation of Amazon waters in the NECC

Aug 2008

Oct. 2007

Conclusions and perspectives

WTRA:Strong salinity control in the western tropical Atlantic but

variability of fCO2 in the NECC still to be determined (CO2

sinks)

Inflluence of the Amazon outflow, eastward propagation in NECC Assess the impact of the strength of the NECC, the Amazon outflow with a Regional Ocean Model (ROMS-PISCES)

NATR and NAST(E):

Sink of CO2 in winter to source in summer

Influence of the Mauritanian upwelling in NATR: extent? Impact?