Presentation on theme: "Oceanic sources and sinks for atmospheric CO 2 Nicolas Gruber (1), S.E Mikaloff-Fletcher (1), A.Jacobson (2), M. Gloor (2), J. L. Sarmiento (2), T. Takahashi."— Presentation transcript:
Oceanic sources and sinks for atmospheric CO 2 Nicolas Gruber (1), S.E Mikaloff-Fletcher (1), A.Jacobson (2), M. Gloor (2), J. L. Sarmiento (2), T. Takahashi (3), and OIP members (1)Department of Atmospheric and Oceanic Sciences & IGPP, UCLA (2)AOS Program, Princeton University (3)Lamont-Doherty Earth Observatory of Columbia (4) Ocean Inversion Project
Takahashi et al. (2002) u 2 a la Wanninkhof et al. (2001) TWO VIEWS OF CO 2 FLUXES IN THE SOUTHERN OCEAN TRANSCOM Gurney et al. (2002) 0.86 Pg C yr -1 0.47±0.40 Pg C yr -1
Basis functions are model simulated footprints of unit emissions from a number of fixed regions Estimate linear combination of basis functions that fits observations in a least squares sense. Inversion is analogous to linear regression footprintsfluxes obs Premultiply both sides by inverse of A INVERSION OF OCEAN INTERIOR OBSERVATIONS estimated fluxes
OCEAN INVERSION METHOD The ocean is divided into n regions (n = 23)
ESTIMATING C gasex AND C ant Since the observed DIC includes the impact of biology, we need to remove this component to obtain a tracer that just reflects the exchange of CO 2 across the air-sea interface of natural and anthropogenic CO 2 : C gasex + C ant = DIC obs - C bio + const C bio : biological component, estimated from nutrients and Alkalinity C ant : anthropogenic component, estimated using the C* method of Gruber et al.  C gasex : gasexchange component, estimated by difference
StudyAir-sea flux South of ~44°S (Pg C yr -1 ) Mean Inversion (10 models)-0.40±0.35 Takahashi et al. (2002) u 2 -0.86 Takahashi et al. (2002) u 3 -0.94 TRANSCOM-0.47±0.40 McNeil et al. (2005)-0.19±0.26 SOUTHERN OCEAN FLUXES
SUMMARY The Southern Ocean is currently a weak sink, a result of the strong uptake flux anthropogenic CO 2 in this region outweighting the outgassing of natural CO 2. This small Southern Ocean sink of about 0.40±0.35 Pg C yr -1 is consistent with most recent analyses, but is much smaller than the flux estimates based on the Takahashi et al. (2002) climatology. The reconstructed oceanic distribution of anthropogenic CO 2 suggests an uptake rate of 2.20±0.25 Pg C yr -1.