[MITgcm-support] SEAICE pkg, unstable HEFF

Wed Mar 30 08:42:44 EDT 2016

Hi Mari,

There’s extra code in your configuration? I haven’t seen this before (in data):
 &PARM06
 trestore=2592000., xr0=0.e+3,xr1=1000.e+3,yr0=0.0,yr1=200.e+3,
 WpmsqC=40.0,
 &
what does that do?

It is a little odd that you can run the ice model without any downwelling (longwave) radiative fluxes (data.exf). This means that the surface (of the ocean or the ice) is constantly loosing heat proportional to T^4 that is not balanced by any atmospheric radiation (no radiation corresponds to an atmosphere at 0Kelvin). I would expect that that would lead sooner or later to excessive ice thicknesses (but only slowly).

Otherwise, I cannot see anything very obviously wrong, except for the advection of snow and the flooding of ice in the case of too much snow:
These should be set to true (or commented out)
 SEAICEadvSnow = .FALSE.,
 SEAICEuseFlooding  = .FALSE.,

I can only speculate that your precipitation is snowing a lot on the ice (depending on your air temperature and ensuing heat flux), and since it cannot be moved away (SEAICEadvSnow = .FALSE., no conversion to ice by flooding, no melting because your atmosphere is at 0K), it causes problems, 

That’s all I can see now without running the configuration myself.

Hope that helps a little,
Martin

> On 30 Mar 2016, at 11:51, Mari Fjalstad Jensen <Mari.F.Jensen at uib.no> wrote:
> 
> Hi Martin,
> thanks for your reply and comments!
> 
> Attached are data* and *_OPTIONS files, let me know if you need more.
> 
> Regarding the freshwater, I add ~1.5e-06 of precipitation (the area was
> 53000km^2, sorry), still a lot though, but not supposed to be realistic.. With 1e-06 precipitation I don't
> get the instability.
> 
> Mari
> 
> On 29.03.2016 18:00, mitgcm-support-request at mitgcm.org wrote:
> 
>> Message: 1
>> Date: Tue, 29 Mar 2016 14:10:41 +0200
>> From: Mari Fjalstad Jensen <Mari.F.Jensen at uib.no>
>> To: mitgcm-support at mitgcm.org
>> Subject: [MITgcm-support] SEAICE pkg, unstable HEFF
>> Message-ID: <56FA70C1.6060302 at uib.no>
>> Content-Type: text/plain; charset=utf-8; format=flowed
>> 
>> Hi,
>> I am having some problems with the seaice pkg.
>> I am doing some simulations with a run for a 1000*2250 km domain, 5km
>> horz resolution and 30 depth levels, SEAICE pkg on.
>> 
>> Freshwater is added through EmP in a roughly 25000 km^2 area.
>> The run crashes after about 10 years when adding 0.08 Sv of
>> precipitation. The problem seems to be in two grid cells where the
>> sea-ice thickness (HEFF) increases with 50 m in one time step (400s).
>> The grid cells are located just at the edge of where I add freshwater. I
>> do not have this problem when adding less or no freshwater.
>> 
>> Any help with which SEAICE parameters to change would be highly appreciated.
>> 
>> # SEAICE parameters
>>   &SEAICE_PARM01
>>        SEAICEwriteState   = .TRUE.,
>>        SEAICEadvScheme    = 33,
>>        SEAICE_initialHEFF = 0.0,
>>        SEAICE_deltaTtherm = 400.,
>>        SEAICE_deltaTdyn   = 400.,
>>        SEAICE_deltaTevp   = 20.,
>>        SEAICE_multDim     = 1,
>>        ICE2WATR           = 0.92D0,
>>   SEAICEadvSnow = .FALSE.,
>>   SEAICEuseFlooding  = .FALSE.,
>> 
>> ----------
>> I have tried varying diffusion/viscosity parameters and domain where I
>> add freshwater without success..
>> 
>> Best Regards,
>> Mari
>> 
>> 
>> 
>> 
>> ------------------------------
>> 
>> Message: 2
>> Date: Tue, 29 Mar 2016 14:52:53 +0200
>> From: Martin Losch <Martin.Losch at awi.de>
>> To: MITgcm Support <mitgcm-support at mitgcm.org>
>> Subject: Re: [MITgcm-support] SEAICE pkg, unstable HEFF
>> Message-ID: <4FFA44FC-51F3-4D10-B2CA-2FF4C053B8F5 at awi.de>
>> Content-Type: text/plain; charset="utf-8"
>> 
>> Hi Mari,
>> 
>> there are many things that can go wrong with such a configuration, so that the information that you provide is not quite sufficient. If you want more help, I?d ask you to send all namelist files (data*) and all *_OPTIONS.h files that you have modified (ie., the *_OPTIONS.h files in the ?code? directory), in particular the SEAICE_OPTIONS.h and CPP_OPTIONS.h file.
>> 
>> based on what you sent I can say this:
>>> On 29 Mar 2016, at 14:10, Mari Fjalstad Jensen <Mari.F.Jensen at uib.no> wrote:
>>> 
>>> Hi,
>>> I am having some problems with the seaice pkg.
>>> I am doing some simulations with a run for a 1000*2250 km domain, 5km horz resolution and 30 depth levels, SEAICE pkg on.
>>> 
>>> Freshwater is added through EmP in a roughly 25000 km^2 area.
>>> The run crashes after about 10 years when adding 0.08 Sv of precipitation. The problem seems to be in two grid cells where the sea-ice thickness (HEFF) increases with 50 m in one time step (400s). The grid cells are located just at the edge of where I add freshwater. I do not have this problem when adding less or no freshwater.
>> How do you add this? Isn?t 0.08 Sv *1e06 (m^3/Sv) / (25000e6m^2) = 3.2e-06 m/s of water a pretty high precipitation rate? How much less do you need to add to avoid the instability?
>>> 
>>> Any help with which SEAICE parameters to change would be highly appreciated.
>>> 
>>> # SEAICE parameters
>>> &SEAICE_PARM01
>>>      SEAICEwriteState   = .TRUE.,
>>>      SEAICEadvScheme    = 33,
>>>      SEAICE_initialHEFF = 0.0,
>>>      SEAICE_deltaTtherm = 400.,
>>>      SEAICE_deltaTdyn   = 400.,
>>>      SEAICE_deltaTevp   = 20.,
>> If you want to use EVP, I recommend using the new schemes of Madlen Kimmritz, which is implemented in the most recent MITgcm, see Kimmritz etal 2015. On the convergence of the modified elastic-viscous-plastic method of solving for sea-ice dynamics. Journal of Computational Physics, 296, 90-100, doi:10.1016/j.jcp.2015.04.051, 2015, and "The adaptive EVP method for solving the sea ice momentum equation?, just accepted in Ocean Modelling: <http://mitgcm.org/~mlosch/adaptiveEVP_accepted.pdf>
>> Some if this is already in the online-documentation. I recommend using parameters SEAICE_evpAlpha=SEAICE_evpBeta=500 and SEAICEnEVPstarSteps = 200 or so. That may not lead to fully converged solutions but they will be more or less smooth.
>> But I think your solution will be just as sane with the default VP parameters (i.e. just comment out deltaTevp), and much better (if smoothness and stability count) with order 10 non-linear iteration steps (NSPEUDOTIMESTEPS = 10 or if you have recent code SEAICEnonLinIterMax=10).
>>>      SEAICE_multDim     = 1,
>>>      ICE2WATR           = 0.92D0,
>>> SEAICEadvSnow = .FALSE.,
>>> SEAICEuseFlooding  = .FALSE.,
>> These two parameters only make sense if there is no snow in the simulations.
>> 
>>> 
>>> ----------
>>> I have tried varying diffusion/viscosity parameters and domain where I add freshwater without success..
>> 
>> Martin
>> 
>>> 
>>> Best Regards,
>>> Mari
>>> 
>>> 
>>> _______________________________________________
>>> MITgcm-support mailing list
>>> MITgcm-support at mitgcm.org
>>> http://mitgcm.org/mailman/listinfo/mitgcm-support
>> 
>> 
>> 
>> 
>> ------------------------------
>> 
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>> 
>> End of MITgcm-support Digest, Vol 153, Issue 30
>> ***********************************************
>> 
> 
> 
> 
> 
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