1. 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
In collaboration with : R. Keeling, M. Mazloff, S. Gille, J. Sprintall (SIO) C. Nevison (CU Boulder) D. Menemenlis (JPL)

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

3. 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

4. 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

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

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

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

8. 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

9. 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)

10. 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

11. New metric to test on models
= 3-4 (Amplitude of observed ratios)
= (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

12. 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

13. 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

14. 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.

15. 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)

16. 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)

17. 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)

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