[MITgcm-support] NLFS=4 with z coordinates.. and sea ice

[Stanislav Martyanov]

Hello Daniel,

In the past, I successfully configured a regional high-resolution Kara Sea
model where I used a pure z coordinate and a non-linear free surface +
SEAICE package. The model is still being used and working, giving good
results.

You are right about possible issues with sea ice if it is rather thick
while you have fine vertical resolution of the upper layer. Because of that
(+ sea-level oscillations due to tides, storm surges, etc) I used the
thickness of the upper level equal to 5 m while using z coordinate, due to
possible sea-ice thickness of 2-3 m in some locations in the Kara Sea +
sea-level oscillations.

Kind Regards,
Stanislav Martyanov

вт, 22 сент. 2026 г. в 15:23, Daniel Goldberg <Dan.Goldberg at ed.ac.uk>:

> thanks J-M! i didn't know about the sIceLoadFac parameter either, so that
> will be an option.
>
> best
> dan
> ------------------------------
> *From:* MITgcm-support <mitgcm-support-bounces at mitgcm.org> on behalf of
> Jean-Michel Campin <jmc at mit.edu>
> *Sent:* Tuesday, September 22, 2026 13:18
> *To:* mitgcm-support at mitgcm.org <mitgcm-support at mitgcm.org>
> *Subject:* Re: [MITgcm-support] NLFS=4 with z coordinates.. and sea ice
>
> Hi Dan,
>
> It should work, not used much without z*, precisely for the reason you
> mentioned,
> see also the Ocean modelling paper, doi:10.1016/j.ocemod.2008.05.005 :
> "Sea ice-ocean coupling using a rescaled vertical coordinate z*"
>
> Note that you could always bring back an inconsistent "levitating" sea ice
> with
> a recently added param (in "data", first namelist): sIceLoadFac=0.,
>
> Cheers,
> Jean-Michel
>
> On Tue, Sep 22, 2026 at 11:18:26AM +0000, Daniel Goldberg wrote:
> > Hello!
> >
> > I am curious if anyone has used nonlinear free surface (NLFS=4) with
> z-coordinates and with the sea ice model?
> >
> > I suspect that it will be limited by the thickness of the top cell
> relative to the sea ice thickness, and am prepared to deal with
> surf_adjustment errors if they occur.
> >
> > But aside from this, Im wondering if there are any numerics/packages
> that simply won't work, of if i will get a RT error simply for trying this
> combination of parameters?
> >
> > Thanks!
> > dan
> >
> > --
> > Daniel Goldberg, PhD (he/him)
> > Reader in Glaciology
> > School of Geosciences, University of Edinburgh
> > Geography Building, Drummond Street, Edinburgh EH8 9XP
> >
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