[MITgcm-support] ice layer modeling -> cube corners?

[Elja Huibregtse]

Dear Dimitris & others,

Unfortunately, I still didn't find the solution to fix my unstable ocean+ice model. While checking the data, I found, however, that velocity-fields show deviant behavior at the corners of the cube (I use a cubed sphere configuration). I attached one horizontal velocity plot, where this behavior is clearly visible. The model becomes, as expected, unstable in one of these 'corner-regions' and blows up.

Could there be something wrong with the coupling between the tiles? Or do I need a larger overlap (in my case: OLx=Oly=5)?
Do you have any idea what is wrong and how to fix it?

Thank you very much in advance!

Elja 




-----Oorspronkelijk bericht-----
Van: mitgcm-support-bounces at mitgcm.org namens Dimitris Menemenlis
Verzonden: di 7/8/2008 3:12
Aan: mitgcm-support at mitgcm.org
Onderwerp: Re: [MITgcm-support] ice layer modeling
 
Elja, that is so cool!  I never would have imagined that pkg/seaice  
could be applied to a 10-km-thick layer of ice!

In your data file, I notice that you have:

useRealFreshWaterFlux=.TRUE.,

This means that you turn on Jean-Michel's sea-ice ocean coupling using  
a rescaled vertical coordinate z*:

http://mitgcm.org/~jmc/iceLoading_accept.pdf

In this configuration the sea ice pushes down on the surface of the  
ocean as in Fig. 1c of paper above.  I think this answers your second  
question.

Regarding your first question, the error that you are getting  
typically occurs when these z* levels are squeezed too thin.  For  
example, this will happen if the bottom of your ice + tidal loading  
gets pushed too close to your shallowest bathymetry.  Starting from a  
pickup near your blow-up, set "monitorFreq=1" then "grep _eta_min  
STDOUT.0000" to see if your minimum sea surface height gets close to  
the bottom of your ocean.

Dimitris Menemenlis
DMenemenlis at gmail.com

On Jul 8, 2008, at 5:12 AM, Elja Huibregtse wrote:

> Dear all,
>
> Currently, I am trying to model a thick (10 kilometers) ice layer on  
> top of an ocean of about 100 kilometers deep (to simulate Jupiter's  
> moon Europa). I implemented the tidal force induced by Jupiter both  
> in the ocean equations (external_forcing.f) and in the ice-layer  
> equations (seaice_lsr.f).
>
> Sooner or later, the model becomes unstable and 'blows up'. The  
> errors are like:
>
> WARNING: r*FacW < hFacInf at       3 pts : bi,bj,Thid,Iter=   1    
> 1   1      7266
>  e.g. at i,j=  17  29 ; rStarFac,H,eta =**********  1.050000E+05   
> 1.087561E+10 -2.871467E+10
> STOP in CALC_R_STAR : too SMALL rStarFacW !
> WARNING: r*FacS < hFacInf at       2 pts : bi,bj,Thid,Iter=   1    
> 1   1      7266
>  e.g. at i,j=  15  30 ; rStarFac,H,eta =**********  1.050000E+05  
> -1.720477E+10  2.505553E+09
> STOP in CALC_R_STAR : too SMALL rStarFacS !
> WARNING: r*FacC < hFacInf at       2 pts : bi,bj,Thid,Iter=   1    
> 1   1      7266
>  e.g. at i,j=  17  29 ; rStarFac,H,eta =**********  1.050000E+05  
> -2.871467E+10
> STOP in CALC_R_STAR : too SMALL rStarFacC !
>
> Initially, I assume a thick ice layer, which will of course cause  
> (some) artificial behavior.
> I tried to force Europa with only 10% of the total forcing. This  
> went well. My intention was to gradually increase the forcing (by  
> using restarts), to prevent too much artificial behavior. However,  
> after increasing the forcing (up to 30%) the model became unstable  
> again.
>
> Do you have some suggestions how to improve my model? Is there maybe  
> something really  trivial I did not include?
> Furthermore, is the ice layer modeled on top of the ocean or is the  
> top ocean layer replaced by the ice-layer?
>
> I attached the data file.
>
> I really appreciate your help!
>
> Thanks in advance,
>
>
> Elja
>
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