[MITgcm-devel] seaice

[Jinlun Zhang]

Martin, you are right, as a maximum, it is not that bad. Sorry for not 
being clear - by advection I meant delta(Uice*hice) or 
delta(Uocean*salinity) kind of things.
Jinlun

Martin Losch wrote:

> 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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>>
>>
>>
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-- 

Jinlun Zhang
Polar Science Center, Applied Physics Laboratory
University of Washington, 1013 NE 40th St, Seattle, WA 98105-6698

Phone: (206)-543-5569;  Fax: (206)-616-3142
zhang at apl.washington.edu
http://psc.apl.washington.edu/pscweb2002/Staff/zhang/zhang.html