[MITgcm-devel] seaice

[Martin Losch]

Hi Jinlun,

sorry about my excitement. You are right, altough the not letting  
seaice modify the freshwater flux leads to a more satifactory  
solution, it does so for the wrong reasons.

The units of the rates:
0.008/(S*rhoFresh) = 0.008/(35*1000) =2.3e-7 m/s = 7 m/year
This is not so dramatic, expecially since this is only the maximum  
growth rate. So I have to keep searching for the "right" reason for  
my problem.

When you say advection, do you mean advection of heff and area? ice  
velocities? I checked: they are approximately one percent of the wind  
speed (which I was told is about right).

Martin

On Feb 14, 2006, at 1:30 AM, Jinlun Zhang wrote:

>
>
> Martin Losch wrote:
>
>> The story continues:
>>
>> I ran my configuration with (always with exf and exf_bulkformulae)
>> 1. full seaice model
>> 2. without seaice model
>> 3. with seaice model but unmodified stresses
>> 4. with seaice model but with unmodified buoyancy fluxes (store  
>> the  fluxes at the beginning of seaice_model and restore them at  
>> the end  of seaice_model)
>>    a. all unmodified
>>    b. only EmPmR unmodified
>>    c. only qnet and qsw unmodified (blows up!!!)
>>
>> Whenever EmPmR is unmodified the circulation is "bad". That is,  
>> the  ACC breaks into the Weddell Sea. In particular runs 2, 4a  
>> and  4b  look reasonable (of course the ice is terrible in a few  
>> cases but I  don't care about that now), but run 1 and 3 are bad.  
>> Unfortunately  the run 4c explodes very quickly and I don't know why.
>>
>> I compared the sfluxtave between run 1 and run 4b (empmr  
>> unmodified  by ice model). The icemodel adds a freshwater flux to  
>> the model that  can be 10 to 20 larger than the atmospheric  
>> freshwater flux (in the  yearly average!!), especially along the  
>> boundary of the Weddell Sea.  This makes the surface waters along  
>> the boundaries much saltier in  run1 (with full seaice) than in  
>> run 4b (everything but EmPmR  modified). As a consquence run4b  
>> shows a strong salinity gradient  from the coast (fresh) to the  
>> center of the Weddell Sea, and a  Weddell Gyre develops, whereas  
>> in run1 (with full seaice) this  gradient is very weak. Comparison  
>> with levitus surface salinity does  not help, because in the mean  
>> there the structure is a different (and  I don't know to what  
>> extend I can believe that).
>>
>> Is it reasonable to have yearly average salt fluxes (sflux) on  
>> the  order of -0.002 to 0.008 (mainly due to the ice model,  
>> instead of  atmospheric fluxes of -0.002 to 0.0006), divide by  
>> s*rhoFresh =  (35*1000) to get freshwater fluxes? May there be a  
>> problem in the  seaice?
>
> Martin, what is the units of these numbers. If the ocean  
> stratification is ok with ice in, as you mentioned earlier, then  
> the problem is perhaps not freshwater flux, but advection.
> Cheers, Jinlun
>
>>
>> Martin
>>
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