Ocean Interior constraints on air-sea fluxes of oxygen and APO: An update

Sara Mikaloff Fletcher & Nicolas Gruber

Department of Atmospheric and Oceanic Sciences & IGPP, UCLA

Thanks to Andy Jacobson, Princeton

Results fromGruber et al. (2001)

Note relatively small sensitivity of APO to large model-model differences in ocean transport in the extra-tropics

OCEAN REGIONS AND O2* DATA

Model Configuration

General Description

Mixing Comments

LL~4°x5° MOM

Seasonally forcedLow Kv/Low Ai

Overly strong stratification in

S.O.

HH~4°x5° MOM

Seasonally forcedHigh Kv/High Ai

Excessive deep convection in S.O.

LHS~4°x5° MOM

Seasonally forced

Low globally Enhanced Kv

South of 55S

Too slow deep ocean overturning

RDS

(standard)

~4°x5° MOM

Seasonally forced

Moderate globally, Enhanced Kv South of 55S

Best fit to observations

ECCO~4° MIT

Adjoint modelLow

Assimilated data from NCEP period

OCEAN TRANSPORT MODELS

Without seasonal rectifier

SUMMARY

• New 27 region inversions appear to give robust estimates of the

air-sea exchange of oxygen with little sensitivity to model

transport.

• Comparison of the modeled APO distribution with observations

gives better agreement than before, particularly in the tropics.

However, most of the improvement is a result of using a

different atmospheric transport model (TM3 instead of GCTM.)

• Discrepancies continue to exist in the high-latitude Southern

hemisphere. We suspect that this is due to ocean model errors.

DISCUSSION POINTS

• The power of APO to constrain annual mean air-sea fluxes of

oxygen is limited, as uncertainties in atmospheric transport and

in the other components of APO are likely overwhelming the

problem.

• It appears to be more fruitful to use APO as a consistency

check for ocean-based estimates of air-sea fluxes of oxygen.

• There appears to be interesting potential to use APO to

evaluate atmospheric transport models, e.g. in their

representation of oceanic boundary layers, or in the transport of

oceanic air over the continents, as proposed earlier.

The End.