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?