[MITgcm-support] Seaice water drag

[Kalyan Shrestha]

Hello everyone,

I am trying to explore baroclinic instability under sea ice. However, in
the MITgcm sea ice model, I noticed that changing the drag doesn't seem to
affect anything, which means that there is something weird happening with
the sea ice-water drag. Let me elaborate this with an example - please
refer the related figure in the dropbox link below.
*https://www.dropbox.com/s/ipcnf2p95w00itp/SeaiceWaterDrag.pdf?dl=0
<https://www.dropbox.com/s/ipcnf2p95w00itp/SeaiceWaterDrag.pdf?dl=0>*

For this, I have designed three numerical experiments, which are
as follows. The only difference in the following three cases is in sea ice
concentration and sea ice water drag, while all other parameters are
identical.
Case A-- sea ice concentration, c =0; and Sea ice-water drag, Cd = 5.35E-03
Case B-- c = 1; Cd = 0
Case C-- c = 1; Cd = 1.32E-03

Physically, Case A and Case B should give the same result because both have
zero sea ice-water stress. On the other hand, Case B and Case C should
behave differently as their drag coefficients have changed. However, the
results are surprising. Contrary to what is expected, Case A and Case B
give unidentical results, whereas Case B and Case C give exactly similar
results. Apart from total kinetic energy vs time plot and salinity contours
in the attached figure, I also checked the energetics and other
diagnostics, and the results do not make physical sense.

Could you please help me to understand this?

Thanks,
Kalyan Shrestha
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