Manfredi ManizzaSIO/UCSD

mmanizza@ucsd.edu

Testing ocean biogeochemical models with atmospheric observations of Oxygen and

Argon in the Southern Hemisphere

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 andbiogeochemical processes at seasonal time-scale.

Seasonal gain and loss of buoyancy of thethe 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

Thermal Net Comm. Prod. Thermal Ventilation

O2 Flux = 1-Thermal + 2-NCP + 3-Ventilation

Spring - Summer Autumn - Winter

(Nevison et al., 2012; Manizza et al., In Press)

Classic O2 Flux metric : Seasonal Net Outgassing

SNO according to Garcia & Keeling (2001)

SNO(t) = Flux_month(t) - Flux_annual_average

MITgcm 2.8 by 2.8 + eco. model; Manizza et al., Tellus B, 2012, In Press

O2 seasonal cycle in models

Naegler et al., Tellus B, 2007

OCMIP modelsGK 2001 climatology depends on wind and HF products and empirical relations with heat flux.

In GK 2001 wind and heat fluxesuse ECMWF products.

Use of Atmos. Obs. & APO

APO = O2 + 1.1 * CO2 (Severinghaus, 1995)

Atmospheric Potential Oxygen

- 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

Naegler et al., Tellus B, 2007

Use of Atmospheric Transport Model (ATM)to translate air-sea fluxes into atmos. [gas]

ATM can introduce an error that canImpact the evaluation of the results

MAIN QUESTION :

Can we try to bypass the use of ATMto test our model and performance onthe seasonal cycle of air-sea fluxes ?

Different ATMs can generate different Results when forced by same fluxes.

Seas. Cycle of APO, Ar & N2 from stations

Cold Bay La Jolla

Cape Grim

Palmer Station

Same phasing (driven by Heat Fluxes)

Difference in seasonal amplitude

Difference in amplitde is due to :1) NCP in warm seasons (outgassing)2) Ventilation in cold seasons (ingassing)

δAr/N2

APO

Scripps Network of Atmospheric Stations

O2 and Ar : same solubilty in seawater

Seas. Cycle of APO, Ar & N2 from stations

Scripps Network of Atmospheric Stations Cold Bay La Jolla

Cape Grim

Palmer Station

δAr/N2

APO

A_(APO) / A_(Ar/N2) = 3-4

How to relate the ratio to oceanicprocesses and test models ?

Focus on the Southern Hemisphere

New metric to test on models

RHS of main equation is equivalent to the slope of the time-integrated fluxesof O2 and Argon in the ocean :

==> NEW METRIC TO DIRECTLY TEST OCEAN MODELS WITHOUT USE OF ATM

= 3-4 (Amplitude of observed ratios)

= 50-60 (Expected value of the new metric)

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 cyclesAr 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 degSea-Ice Model DIC package, PO4, Fe, light limitation O2 and CO2 cycleAr, N2, and O2-Thermal explicit tracers (plus N2O cycle)NCEP forcing , open boundary conditions

Results I – Time- Integrated Fluxes

30-45 S 45 – 55 S 55-80 S 40- 60 S

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

A_(APO) / A_(Ar/N2) = 2.2 – 2.4

Atmospheric Stations

ATM runs (PlankTOM10)

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

F_O2 / F_Ar ~ 50

F_O2(Th) /F_Ar ~ 20-25

Modeled metric (Total O2) varies latitudinally

Modeled metric (Thermal O2 ONLY)does not vary latitudinally

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 testingphysical models (NSF-funded project using ECCO solutions)

Conclusions

Possible other applications of this metric : evaluating next generation of IPCC models in their ocean bgc components (project funded by NASA)

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 ECCOsolutions for the thermal-only part (project funded by NSF – Chem. Oc.) ?? Use of O2-Th/Ar ratio, for physics only.

More to do with ECCO & ECCO-3

2 – Using subdomain of SOSE-like set-up to explain the chlorophyll transition from west to east of the Drake Passage (Pending NASA funding)

1 – Interannual variations of O2/Ar in the global ocean (NSF Funded, collaborationwith P. Heimbach)

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))

6 – The impact of aeolian Fe supply to the biogeochemistry of the Southern Oceanusing SOSE-like se-tup & Bling (led by Amato Evan at SIO, to be submitted to NSF)

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)

Air-sea inert gas flux : seasonal cycle

ThermalThermal

Ar and N2 Flux = F_Therm. + F_Vent.

Spring - Summer Autumn - Winter