[MITgcm-support] funky ice dynamics in doubly periodic domain

[Dimitris Menemenlis]

Hi Jean, how big is your domain, and which ECMWF wind product are you using?
And what does your effective sea ice thickness look like spatially as a function of time,
especially at boundaries of your domain where you are bound to have some surface
stress divergence or convergence?  Do you get any cracks?

The reason I ask is because maybe what you are seeing is exactly what you should expect
to see.  If there is not sufficient divergent or convergent wind stress on the ice, it could move
as a monolithic slab as it thickens.  That is the sea ice cover is mostly driven by internal
rather than surface stress, there is sufficient mass to smooth out wind speed fluctuations,
and it integrates surface stress over space time.

One way to test this hypothesis is to reduce ice strength, say:
      SEAICE_strength    = 1  _d +04
to see if the onset of the “steady ice speed” period happens a little later.

Another would be to close boundaries at edges of your domain then your ice
should be immobilized (maybe?).

Dimitris Menemenlis

> On Feb 22, 2016, at 10:22 PM, Jean Mensa <jean.mensa at yale.edu> wrote:
> 
> Hi all,
> I have a doubly periodic high resolution simulation forced with ECMWF atmospheric forcing (forcings.png) running the seaice pkg with VP rheology. Thermodynamics variables look good (ice.png) but ice velocity does something funky and I am not sure why. During summer season ice thickness is minimum (H_I) and concentration low (A_I) and ice dynamics seems to be driven by wind stress. This is all good and fine except that during winter ice velocity (S_I) seems to converge to some constant value decoupling from wind stress. This does not seem right to me. Is that an artifact of the doubly periodic configuration? Notice that the simulation runs fine and gives no failed convergence warnings.
> Thanks,
> Jean