NOCES meeting Plymouth, 2005 June Top-down v.s. bottom-up estimates of air-sea CO 2 fluxes : No winner so far … P. Bousquet, A. Idelkadi, C. Carouge, P. Peylin, Z. Lachkar, Laboratoire des Sciences du Climat et de l’Environnement (France) and NOCES WP1 modelers With the contributions of P. J. Rayner (LSCE), C. Rodenbeck (MPI), G. McKinley (MIT)

Forward modeling : Impact of spatio-temporal air-sea fluxes of CO2 and O2 (WP1) on atmospheric concentrations Penetration of marin air within Eurasian continent Inverse modeling : Interannual air-sea flux estimates with uncertainties at a regional scale on a monthly basis Comparison of inversion estimates with fluxes from WP1 Time schedule : Year 1 : - LMDZt transport model with interannual meteorologyDONE Yr1 Year 2 : - forward modeling using air-sea fluxes from WP1 DONE - Comparison with atmospheric observations (AEROCARB)DONE - Set up of inversion procedure DONE Yr2 Year 3 : - Inversions using air-sea fluxes from WP1NOT DONE - Comparison with WP1 estimates and other estimatesDONE WP2 : Atmospheric modeling of interannual variability

CO 2 Atmospheric network

Spatial discretisation of atmospheric inversion

LMDZt, a GCM with offline, retro-transport and zooming capabilities 96x72 cells : 3.75°x2.5°---> 0.5°x0.5° (Europe) 19/38 hybrids vertival layers Direct transport nudged on ECMWF analysis Back-transport capability Jour 2Jour 4

Forward and inverse simulations Forward modeling : Impact of IAV of ocean CO 2 flux at atm. stations around Europe for different ocean models Impact of IAV of transport of ocean CO 2 fluxes at atm. Stations around Europe Inverse modeling : Impact of different spatio-temporal ocean flux priors on inversion results Comparison between inverse results to ocean models outputs at basin scale on a monthly basis

Atmospheric Inversions Atmospheric concentrations Surface fluxes Yearly observations MBL & coastal sites Monthly observations MBL & coastal sites Synoptic observations All sites (continental) Transport model - Coarse global models - Global high resolution models, zoomable, nested or regional models Monthly flux estimates Large regions Monthly flux estimates Model resolution or Small regions Yearly flux estimates Large regions

Spatial structure of modelled air-sea CO 2 fluxes COCO-NEMURO ORCA2 (MPI) ORCA2 (IPSL) Takahashi ClimatologyMPI model MIT model gC/m 2 /yr

Temporal variations of air-sea CO 2 fluxes (1)

Temporal variations of air-sea CO 2 fluxes (2)

Temporal variations of air-sea CO 2 fluxes (3)

Temporal variations of air-sea CO 2 fluxes (4)

Temporal variations of air-sea CO 2 fluxes (5)

Temporal variations of air-sea CO 2 fluxes (6)

Top-down inversions v.s. bottom-up ocean models (1)

Top-down inversions v.s. bottom-up ocean models (2)

Top-down inversions v.s. bottom-up ocean models (1)

Top-down inversions v.s. bottom-up ocean models (1’) Mc Kinley et al., 2004

Top-down inversions v.s. bottom-up ocean models (3)

Top-down inversions v.s. bottom-up ocean models (4) Peylin et al., 2005

Top-down inversions v.s. bottom-up ocean models (5)

Top-down inversions v.s. bottom-up ocean models (6)

Top-down inversions - TRANSCOM 3 experiment (1)

Top-down inversions - TRANSCOM 3 experiment (2)

Top-down inversions - TRANSCOM 3 experiment (3)

Top-down inversions - TRANSCOM 3 experiment (4)

NOCES June 2005, Plymouth, UK 2 In this study we analyze the variations of DIC, TA, Temperature and salinity observed along the same track, between Iceland and the Newfoundland over the period Ocean measurements Cruise track : The analysis is focus on the open ocean region, 53°N-62°N/45°W-20°W Iceland Corbiere, pers. com

And observations ? (1) Mace-Head Océan Globalview North Atlantic pCO 2 measurements Metzl et al., pers. Comm.

NOCES June 2005, Plymouth, UK 11 SURATLANT CO2 flux Inversion CO2 monthly flux The sink is lower than observed and the model doesn’t capture the seasonal variation and the extreme event in 2003 And observations ? (2) Corbiere, pers. com

Ocean model is close to the observations for the period and he does capture the seasonal variability ORCA-PISCES Flux SURATLANT Flux NOCES June 2005, Plymouth, UK 14 And observations ? (3) Corbiere, pers. com

And observations ? (2) Peylin et al., 2005

And observations ? (3) Gruber et al., 2002

And observations ? (4) Metzl et al., Liège 2-6 May 2005

Atmospheric forward modelling MHD SCH HUN ORL Contribution of air-sea fluxes to CO 2 IAV at atmospheric stations (LMDZ model)

Conclusions (temporary..) IAV of air-sea CO2 fluxes in ocean models mostly stays within ± 0.1 GtC/yr at basin scale except in the equatorial pacific (± 0.3 GtC/yr) ---> counteracting effects occur at least in the North Atlantic: DIC/SST, convection/export, DIC/Alkalinity, other ?? IAV of air-sea CO2 fluxes in inversions is larger, up to ± 0.5GtC/yr at basin scale. IAV of Pacific ocean and austral ocean only slightly dominate other ocean regions. ---> Effects of the inversion algorithm & set-up (prior error structure, aggregation error,..) and of the choice and the number of atmospheric stations used (critical when including continental sites). Agreement in equatorial pacific and in the fact that pacific dominates IAV.

Climate and weather fields Atmospheric Transport model Atmospheric measurements Towards a carbon cycle data assimilation system optimized Fluxes Emissions inventories Ecological measurements Forest/soil inventories Eddy Flux towers Remote sensing of Atm. conc Data assimilation link optimized model parameters Model of land surface fluxes Remote sensing of Vegetation properties