[MITgcm-support] SEAICE, very thick ice

Martin Losch Martin.Losch at awi.de
Mon May 18 12:23:33 EDT 2020

Hi Stanislav,

the open boundary conditions for sea ice were probably not made for this type of situation (have them in the middle of an active ice region where ice is confined by topography). 

One thing that will always reduce excessive ridging is turning off the default pressure replacement method (set SEAICE_pressReplFac = 0.). With pressure replacement, stagnant ice tends to be pushed and piled up in corners and bays, because the replacement pressure (so the ice strength) reduces dramaticall for small strain rates (when nothing is moving anymore).

other than that, I would probably try the option “OBCS_SEAICE_COMPUTE_UVICE”. This is only implemented for OBCS_UVICE_OLD, but you can easily transfer that implementation of a Neumann boundary conditions (du/dn = 0 across the boundary) from seaice_adjust_uvice.F to seaice_apply_uvice.F In this way, the ice velocities will be determined only by forcing in the interior. 

But you should maybe first check, if you have excessive flux of ice over your boundaries. At least the northwest corner doesn’t look like that in your plots.


> On 18. May 2020, at 17:38, Stanislav Martyanov <martyanov.sd at gmail.com> wrote:
> Hello everyone!
> I get very thick sea ice at several locations in the high-res Kara Sea model domain (horizontal resolution is 500-1200 m). Interestingly, the general pattern of sea ice concentration and thickness is OK compared to MERCATOR ocean reanalysis, but in some regions the modeled HEFF is reported by the monitor to be about 15 m after 5 months of integration (starting from realistic initial conditions). I have attached the figure to clarify what I mean and where it happens.
> I suspect the ridging process near the open boundaries to be involved in this situation, but I do not know what can be done with it.
> Such HEFF also produce problems in vertical layers when useRealFreshWaterFlux is TRUE, but I checked that such too thick ice is also produced when useRealFreshWaterFlux is OFF, so it is not a cause (at least, not the main cause).
> Unfortunately, there exist too many options to just iterate through all of them.
> May be you can advise what can be done to mitigate such overestimated HEFF? My preliminary suggestions are as follows, but I am not sure about them:
> - to switch off the uice and vice at the OBCS?
> - to set SEAICE_no_slip=TRUE to reduce the sea ice velocities near the coasts to prevent enhanced ridging?
> - to use sponge at the open boundaries?
> - there was a CPP key OBCS_SEAICE_AVOID_CONVERGENCE, but it is only for OBCS_UVICE_OLD which, in turn, is undefined by default and even may be not implemented, as stated.
> Any advice is very welcome!
> Stanislav
> PS: I use a SEAICE package configuration which is very close to the default one. What I have changed is:
> SEAICEadvScheme = 33,
> SEAICE_multDim = 1,
> <SEAICE_OPTIONS.h><data><CPP_OPTIONS.h><OBCS_OPTIONS.h><data.obcs><FIGURE HEFF.png>_______________________________________________
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