[MITgcm-devel] seaice dynamics in a 2-D set-up

[Martin Losch]

Hi Jean-Michel,

do you think that Ny=1 is the problem? I don’t think so, because always the LSR solver converges only very slowly. I see the same problem when I start from a horizonally homogeneous ice distribution. It takes a while before the ice starts moving, ie. from uice=vice=0 => solver does not do anything => doesn’t cost anything, but when it starts, LSR picks up, does not converge and uses a lot of time.

If you want a converging (but still expensive) solver use JFNK (for a start the parameters in offline_exf_seaice.dyn_jfnk should be OK, also have a look at SEAICE_OPTIONS.h!)

Also, convergence is always improved for larger seaice_eps (default is 1e-11, but 2e-9 is used very often), and a smoother/better regularization (not implemented: deltaCreg = deltaC + seaice_eps).

Martin
> On 04 Mar 2015, at 17:55, Jean-Michel Campin <jmc at ocean.mit.edu> wrote:
> 
> Hi Martin and others,
> 
> I am trying to run a simple oceanic 2-D (Y-Z) set-up with seaice dynamics.
> It starts without seaice and before seaice forms the LSR solver
> converges (not just doing 1 iteration, but within 10-12 iters).
> 
> But as soon as there is seaice, it stops converging and
> more than half of the CPU time is spent in SEAICE_DYNSOLVER
> (despite the fact that I have 50 levels + SOM advection scheme).
> 
> I can reduce the max number of LSR iterations (SOLV_MAX_ITERS),
> faster but still not great.
> I tried separatly SEAICEuseMultiTileSolver=T and SEAICE_OLx,y=1
> but the improvement is very marginal.
> 
> I am tempting to reduce even more SOLV_MAX_ITERS but start to worry
> about what the ice velocity will be.
> Is there anything I could try ?
> and should we think of some code modification for the specific case
> where Nx=1 or Ny=1 ?
> 
> Cheers,
> Jean-Michel
> 
> _______________________________________________
> MITgcm-devel mailing list
> MITgcm-devel at mitgcm.org
> http://mitgcm.org/mailman/listinfo/mitgcm-devel