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The primary goal of this meeting was to update interested parties on the translation of the Sarmiento group's OM1 configurations from MOM3 to MOM4, further development of OM1p5, and status of the various biogeochemical modules.

OM1 availability:

Jennifer Simeon has put together a suite of configurations of the Sarmiento group's OM1 configurations from MOM3 to MOM4. These include the various:
Low-Low
High-High
High-Low
Low-High
Low-Low, high south
P1 (original OCMIP2 submission)
P2 (various modifications put together by Rick Slater)
P2a (various modifications put together by P. Swathi)
Described in Gnanadesikan et al. (2002, DSR-II). Dunne is currently re-synchronizing this code and xml with the newest version of the model, which will hopefully be ready by the end of the week.

OM1p5 Development progress:

Since the Dec 17, 2003 meeting, a number of experiments ave been performed:
Conversion to MOM4p0 with new field manager
Water flux/Virtual flux comparisons with new code trials - the distinction proved to be quite large, but to this point, a mechanism of bringing the two simulations together was never found (as far as Dunne knows)
Neutral physics tinkering - the model is currently using the neutral physics option "neutral_sine_taper" (turning GM off in near the surface) as well as the option "neutral_linear_gm_taper" (keeping some GM on in high slope regions, rather than turning it completely off). These increased stratification in the southern ocean considerably when no slinity restoring was applied.
Bryan-Lewis latitude transition - there is now an option for latitudinally varying Bryan-Lewis mixing (symmetric about the equator), similar to the "High South" cases in OM1.
Tidal mixing - we tried a case of including tidal mixing, but it didn't seem to affect the solution very much.

Current model forcing:

NCAR monthly climatology for incoming shortwave, longwave and freshwater fluxes, German OMIP daily wind stress and salinity restoring from the World Ocean Atlas, 2001 database (averaged Salinity in upper 40 m)

Continuing Problems:

How to preserve overturning in the long-term... getting better, but still shakey

How to retain AIW signal? again, not nearly as well a defined salinity minimum as we would like, especially considering its probable importance in nutrient supply to the tropics (Sarmiento et al., 2004).

Results with current OM1p5:

Zonal mean Salinity drift over 370 years was shown, demonstrating the erosion of AIW low slinity in favor of low salinities in the deep, southern ocean... still too much vertical exchange - the historical problem with these models.

CFC results reproduce observed features in general, and look to be an improvement over the OM1 Prince 2 model (Slater), but initial condition of World Ocean Atlas 2001 (rather than spun-up physics) is probably a factor, since OM1p5 is using initally realistic geostrophy. Biggest problems are still too much penetration in NADW and ABW.

Primary production in current prognostic model reflects problems in nutrient regeneration and iron cycling

Comparison of iron cycling in 1-D, steady state and model suggests that there is a problem either with the code itself, the initial condition, or that the timescale to reach steady state is exceedingly long

Status of Biogeochemical modules:

Age - module is ready

OCMIP2 CFC - module is ready (bug found in code in January)

OCMIP2 Biotic (Alk, DIC, PO_4, DOP, O_2) - module is ready

OCMIP2 Abiotic (DIC, DI^1^4C) - module is ready

OCMIP2 Anthropogenic CO_2 - on the list, but no timeline yet

Multi-element restoring (with ^1^8O_2) - is being resynchronized into code

Prognostic Model - is ready, but parameter values are being set

Prognostic Model with isotopes - hopefully done in the spring in collaboration between John Dunne and Galen McKinley

Argon - module is being developed by Galen McKinley

Results of long OM1p5 OCMIP2 Biotic Runs:

Gnanadesikan presented results of 310 year runs of the OM1p5 OCMIP2 Biotic configuration showing large temperature drifts at depth due to a cooling (and freshening) of Antarctic Bottom Water.

Oxygen distributions are much improved over OM1 simulations, however.

Next Steps:

1) We are still waiting for an NCAR climatology. As OM3-omip has the same problem as OM1p5, and CM2 has the opposite problem of too strong NADW, we believe that the forcing is the problem.

2) Gnanadesikan has promised to look at the heat and freashwater fluxes.

3) Dunne will check CsCO_3 fluxes (subsequently found to be 10x too big - new simulations with lower coefficient look better).

4) Dunne will try lowering inital phytoplankton iron levels (subsequently also found to be 10x too big - new simulations with lower coefficient look better).

Dunne's full powerpoint presentation can be downloaded HERE.

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