Manfredi Manizza SIO/UCSD mmanizza@ucsd.edu Testing ocean biogeochemical models with atmospheric observations of Oxygen and Argon in the Southern Hemisphere Manfredi Manizza SIO/UCSD mmanizza@ucsd.edu In collaboration with : R. Keeling, M. Mazloff, S. Gille, J. Sprintall (SIO) C. Nevison (CU Boulder) D. Menemenlis (JPL)

Outline 1) Introduction : oceanic O2 seasonal cycle 2) Ocean Processes, Atm. Observations, and Theory 3) Methods : Theory, New Metrics & Models 4) Results and Conclusions

Seasonal O2 cycle in the upper ocean Strong coupling between physics and biogeochemical processes at seasonal time-scale. Seasonal gain and loss of buoyancy of the the water column drives O2 vertical distribution Seasonal changes in O2 vertical distribution impacts seasonal cycle of air-sea fluxes

Air-sea O2 gas flux : seasonal cycle O2 Flux = 1-Thermal + 2-NCP + 3-Ventilation (Nevison et al., 2012; Manizza et al., In Press) Thermal Net Comm. Prod. Ventilation Thermal Spring - Summer Autumn - Winter

Classic O2 Flux metric : Seasonal Net Outgassing MITgcm 2.8 by 2.8 + eco. model; Manizza et al., Tellus B, 2012, In Press SNO(t) = Flux_month(t) - Flux_annual_average SNO according to Garcia & Keeling (2001)

O2 seasonal cycle in models OCMIP models GK 2001 climatology depends on wind and HF products and empirical relations with heat flux. In GK 2001 wind and heat fluxes use ECMWF products. Naegler et al., Tellus B, 2007

Atmospheric Potential Oxygen APO = O2 + 1.1 * CO2 (Severinghaus, 1995) Use of Atmos. Obs. & APO Atmospheric Potential Oxygen APO = O2 + 1.1 * CO2 (Severinghaus, 1995) - O : C = 1.1 ratio in Land Plant photosysnthesis APO tells us about atmopsheric O2 changes driven by oceanic processes ONLY.

Evaluating ocean bgc models Use of Atmospheric Transport Model (ATM) to translate air-sea fluxes into atmos. [gas] ATM can introduce an error that can Impact the evaluation of the results Different ATMs can generate different Results when forced by same fluxes. MAIN QUESTION : Can we try to bypass the use of ATM to test our model and performance on the seasonal cycle of air-sea fluxes ? Naegler et al., Tellus B, 2007

Seas. Cycle of APO, Ar & N2 from stations Scripps Network of Atmospheric Stations Cold Bay La Jolla δAr/N2 APO Same phasing (driven by Heat Fluxes) O2 and Ar : same solubilty in seawater Cape Grim Difference in seasonal amplitude Palmer Station Difference in amplitde is due to : 1) NCP in warm seasons (outgassing) 2) Ventilation in cold seasons (ingassing)

Seas. Cycle of APO, Ar & N2 from stations Scripps Network of Atmospheric Stations Cold Bay La Jolla δAr/N2 APO A_(APO) / A_(Ar/N2) = 3-4 How to relate the ratio to oceanic processes and test models ? Cape Grim Palmer Station Focus on the Southern Hemisphere

New metric to test on models = 3-4 (Amplitude of observed ratios) = 50-60 (Expected value of the new metric) RHS of main equation is equivalent to the slope of the time-integrated fluxes of O2 and Argon in the ocean : ==> NEW METRIC TO DIRECTLY TEST OCEAN MODELS WITHOUT USE OF ATM

Ocean bgc models to test PlankTOM10 : Global configured, 0.5 – 2.0 Horizontal resolution Embedded into NEMO3 + LIM sea-ice model Ecosystem dynamics with 10 PFTs, nuts+Fe+light limitation. O2 and CO2 cycles Ar and N2 fluxes computed according to Jin et al., 2007 (Heat Flx) 3 Runs : NCEP, ECMWF, JPL Winds. (Le Quere et al., 2010) MITgcm : Southern Ocean region (northern limit of 30 S), 1/6 deg Sea-Ice Model DIC package, PO4, Fe, light limitation O2 and CO2 cycle Ar, N2, and O2-Thermal explicit tracers (plus N2O cycle) NCEP forcing , open boundary conditions

Results I – Time- Integrated Fluxes PlanktOM10 – JPL 65.7 50.3 25.2 50.9 PlanktOM10 – NCEP 61.7 47 34 49.3 PlanktOM10 - ECMWF 61.9 48.9 35 50.4 MITgcm – NoFe 23.6 47.4 106 52.1 MITgcm – Fe

Results II – Cross check with ATM A_(APO) / A_(Ar/N2) = 3-4 Atmospheric Stations ATM runs (PlankTOM10) A_(APO) / A_(Ar/N2) = 2.2 – 2.4 Mismatch still remains due to the use of the ATM with its uncertainty associated with the misrepresentation of atmospheric circulation/physics.

Results III – Metric Latitudinal Variations Modeled metric (Total O2) varies latitudinally F_O2 / F_Ar ~ 50 Modeled metric (Thermal O2 ONLY) does not vary latitudinally F_O2(Th) /F_Ar ~ 20-25 1) Latitudinal variations of metric O2/Ar could be due to different biogeochemical regimes in the Southern Ocean 2) Second metric O2(Th)/Ar can also be used for testing physical models (NSF-funded project using ECCO solutions)

Conclusions Comparison with model results shows the potential of the new metric to evaluate the O2/Ar seasonal cycle of bgc models although the latitudinal factor plays a role. ATM runs confirm that even if the metric/model agreement is good the amplitude ratios do not agree : back to original problem of the use of ATM.... Can this new metric also be used as indirect test for ECCO solutions for the thermal-only part (project funded by NSF – Chem. Oc.) ?? Use of O2-Th/Ar ratio, for physics only. Possible other applications of this metric : evaluating next generation of IPCC models in their ocean bgc components (project funded by NASA)

More to do with ECCO & ECCO-3 1 – Interannual variations of O2/Ar in the global ocean (NSF Funded, collaboration with P. Heimbach) 2 – Using subdomain of SOSE-like set-up to explain the chlorophyll transition from west to east of the Drake Passage (Pending NASA funding) 3 – The impact of future climate warming on the Arctic Ecosystem by using 18 Km regional Arctic Ocean set-up with Darwin model (Pending NFS approval, collaboration with U. Laval, Canada) 4 – The impact of melt ponds on the productivity of Western Arctic Ocean with Subregional region Arctic set-up with Darwin code (Pending NFS approval, collaboration with G. Mitchell (SIO), M. Kahru (SIO), N. Bates (BIOS)) 5 – Assessing the Net Community Production of the Arctic Ocean with a future network of atmospheric observations (Pending NSF funding, in collaboration with R. Keeling and Cindy Nevison) 6 – The impact of aeolian Fe supply to the biogeochemistry of the Southern Ocean using SOSE-like se-tup & Bling (led by Amato Evan at SIO, to be submitted to NSF)

Air-sea inert gas flux : seasonal cycle Ar and N2 Flux = F_Therm. + F_Vent. Thermal Thermal Spring - Summer Autumn - Winter