[MITgcm-support] seaice model

[Dimitris Menemenlis]

> Last night, instead of getting a good night's sleep, it tried (and 
> managed) to get the global_ocean.cs32x15 going with the seaice package.

Great.  There is a serious push going on to optimize this config
(Jean-Michel is using it for coupled-climate work and Patrick and I will
use it as a prototype global-ocean and sea-ice adjoint-model assimilation
set-up).  So this is the right config to be in.

> But the problems I have there are the same, plus, with the cubed sphere 
> grid I no longer know what I am doing (o: But essentially, the same 

There's a bunch of matlab and other diagnostics for looking at stuff.
I think it's worth the effort getting used to this grid ... eventually
you will get hooked and become an addict like the rest of us, except
for Alistair who leaves us to swallow his dust and is always moving to
newer and greener pastures.

> thing happens as with lat-lon grid. Ice thicknesses become very large, 
> huge freshwater flux out of the ocean, strong horizontal divergences in 
> the ocean, large vertical velocities and violation of the vertical 
> cfl-criterion. If I reduce the timestep even further, the model runs 
> longer but eventually it blows up, too (all after less than a year of 
> integration).

I was looking back at some preliminary comparisons that I did
of pkg/thsice and of pkg/seaice, with and without dynamics
in the 32x32x6x15 config.  All three integrations ran fine
for five years and there does not seem to be any anomalous
behavior.  But I am integrating all three with 1 hour time
steps.   So maybe it's just a time step issue?

> I have one suspicion: because of the coarse resolution, also in the 
> vertical, vertical fluxes are poorly represented and the dense 
> (cold,salty) water in the top 50m cannot be replaced by warmer, fresh 
> water from below quickly enough, so that there is no (warming) ocean 
> heat flux, that can balance atmospheric fluxes. The fact, that with 
> implicit diffusion as convective scheme with a huge ivdc_kappa=100, 
> makes the model last longest, supports this suspicion. Also the lack
> of convective flux may be compensated by unrealistically high vertical
> velocities, which then lead to the violation of the clf-criterion.

I don't understand why you don't mix vertically.  Both KPP and convective
adjustment will not allow dense water on top of light water to exist ...
unless, there is a problem with equation of state.  Did you mention you get
salinities of 500 PSU?  This would probably be outside the range of the
equation of state then and all bets are off as to what would happen.

> What I find puzzling is the feature before the 
> coast of Venezuela, particularily because it runs along the interface 
> between two tiles. What is that?

Martin, did you turn on biharmonic horizontal terms by any chance?
There is a known bug with the exchange routines for biharmonic that
Chris Hill is working on, but I did not expect the impact to be so big.

D.

-- 
Dimitris Menemenlis <menemenlis at jpl.nasa.gov>
Jet Propulsion Lab, California Insitute of Technology
MS 300-323, 4800 Oak Grove Dr, Pasadena CA 91109-8099
tel: 818-354-1656;  fax: 818-393-6720