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Seasonal variability of CO 2 air-sea fluxes and DIC in the Southern Pacific Ocean

Seasonal variability of CO 2 air-sea fluxes and DIC in the Southern Pacific Ocean. Leticia Barbero , Jacqueline Boutin, Liliane Merlivat. 4th CarboOcean meeting, Dourdan, France 8-12 December 2008. Buoy and ship trajectories in the Southern Pacific Ocean. SAZ. STF. SAF.

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Seasonal variability of CO 2 air-sea fluxes and DIC in the Southern Pacific Ocean

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  1. Seasonal variability of CO2 air-sea fluxes and DIC in the Southern Pacific Ocean Leticia Barbero, Jacqueline Boutin, Liliane Merlivat 4th CarboOcean meeting, Dourdan, France 8-12 December 2008

  2. Buoy and ship trajectories in the Southern Pacific Ocean SAZ STF SAF CARIOCA 01110  April/2004-April/2005 CARIOCA 03740  April/2004-June/2005 Palmer US Ships  April-May/2004 March/2005 September/2005 September/2006 • STF: Climatoligical (Orsi) • SAF: Altimetry data (J.B. Sallée)

  3. Buoy trajectories colour-coded for month STF SAZ SAF Palmer Ships: April-May/2004 March/2005 September/2005 September/2006

  4. fCO2 (µatm) measured by CARIOCA and ships AT computed from SST,SSS (Lee et al., 2006) DIC computed from fCO2 and AT (Mehrbach et al. (1973) after Dickson and Millero (1987) )

  5. DIC (µmol/kg) computed along trajectories • ARGO floats co-located in time and space used to compute mixed layer depth (MLD)

  6. 220 data points (0.5% of total) No data for November Late winter: deep MLD, rich DIC values In order to increase data: Dong et al. (2008) MLD climatology for Southern Ocean

  7. Buoy and ship DIC data vs. Dong et al.’s (2008) climatological MLD (m) Jan. Aug. 100%  46000 data points Oct. Deep MLD-rich DIC Sep.

  8. DIC  hyperbolic f(MLD) σ = 19 µmol/kg DIC = a + b*MLD + c*SST  σ = 9.7 µmol/kg Similar algorithm for fCO2: fCO2 = a’ + b’*MLD + c’*SST  σ = 16 µatm For |MLD| > 100m: fCO2 = a’’ + b’’*MLD + c’’*SST  σ = 8 µatm

  9. MLD (m) SST (ºC) August 2005 Dong et al. (2008), Density difference criteria, Δρ = 0.03 kg m-3 SST, WOA 2005 : Objective analyzed mean

  10. Estimation results for August 2005 Exchange coefficient, Kw (Sweeney et al., 2007) ΔpCO2 µatm 0.04 0.08 0.12 Mol m-2 yr-1µatm Weekly Quickscat winds from Ifremer Sea-air flux (mmol m-2 d-1)

  11. Exchange coefficient, Kw (Sweeney et al., 2007) ΔpCO2 µatm 0.04 0.08 0.12 Mol m-2 yr-1µatm Air-sea CO2 flux for August 2005 Our study Takahashi et al. (2009) • Flux estimates (Pg C/year), Kw Sweeney et al., 2007: • McNeil et al. (2007), 40-50ºS: 0.92 • Takahashi et al. (2009), Pacific Oc., 14-50ºS: 0.4 • Boutin et al. (2008), SAZ: 0.67 • This study, SAZ Pacific Oc (72% of total): 0.81 (mmol m-2 d-1)

  12. Jan. Aug. Estimation of biological production DIC and AT vs. time DIC and SST vs. time Sunrise Sunset

  13. Chl-a from MODISA-SEAWIFS weekly average Net Community Production: F = air-sea flux h = MLD No direct relationship between satellite Chl-a and NCP Method described in detail by Merlivat et al. (2008)

  14. In summary: • Estimates of air-sea CO2 flux in SAZ in the Pacific Ocean: 0.81 Pg C yr-1. • Lack of buoy and ship data in big area on the North-eastern Pacific SAZ. • Large variability in DIC during the summer months  estimates of NCP (0.5-1.22 µmol kg-1 day-1). Questions remain concerning how representative these values are. Is this an intermittent event or can we extract a mean value? • No direct correlation between NCP and satellite products for low chlorophyll-a concentrations. • Still a work in progress!

  15. THANK YOU FOR YOUR ATTENTION

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