[MITgcm-devel] seaice_solve4temp.F cleaning update

[Ian Fenty]

J-M,
> I am more familiar with non-zero heat capacity seaice (this was my "Sea-Ice physics"
> section), and in this case, it's clear that the distinction has to be made.
> But even with zero heat capacity, the vertical profile of temp in snow+ice
> will be monotonous, the surface is @ tmelt=0.degC, the bottom is @ seawater-Tfreeze
> = -1.9 in this simple case, so anywhere in the snow layer t<  tmelt=0 except @ the
> surface where t=tmelt, so that no interior snow melting. And the surface snow melting
> should be just proportinal to the heat convergence at the surface, i.e. F_c - F_ia
> (convention: +=up) (and not just -F_ia as it is now),
> and the conductive heat flux F_c<  0 should be used to melt seaice at the bottom
> according to the heat flux convergence @ the bottom: F_ocean - F_c
> with F_ocean(+=up) = ocean turbulent heat flux @ the ice-ocean interface,

Yes, I think I see it now.  You are arguing that when there is net heat 
flux convergence at the surface and F_c < 0 - which occurs when 
T_ice(surface) < T_ice(base) - then F_c represents conducting heat away 
from the surface not, down the monotonic gradient, towards the base and 
not converging at the surface.  In such a situation we must reconsider 
heat flux convergence at the base.  Since T_ocean >= T_freeze and 
T_ice(base) = T_freeze < T_ice(base+delta) heat must be converging at 
the base and therefore it should be used to melt.  Is that right?

-Ian

>
>> I'm afraid I don't see the answer in the Nov 2010 discussion.
> The reference to the "Nov 2010 discussion" was meant to be understood
> in the context of "If we follow this route", i.e., if we make this
> distinction between F_ia and F_c, which I re-stated just after:
> "but it only makes a difference if we export Fc to seaice_growth".
> But, the big problem is that the link I sent was not the good one !
> Sorry for that. The response I wanted to point to was from the day after,
> Dec 01, 2010, same discussion, same subject:
> http://mitgcm.org/pipermail/mitgcm-devel/2010-December/004410.html
> Hope it's more clear now.
>
> Cheers,
> Jean-Michel
>
>>> If we follow this route, then it makes sense, after the tsurf iteration,
>> -Ian
>>
>>
>>> And use the surface heat flux convergence = Fc - F_ia to do surface melting.
>>>
>>> If we follow this route, then it makes sense, after the tsurf iteration,
>>> to update the atmospheric heat flux F_ia using the linearized approximation
>>> in order to conserve and to keep exactly Fc = F_ia when no surface melting.
>>> I tried to make this point a year ago, in this discussion:
>>> http://mitgcm.org/pipermail/mitgcm-devel/2010-November/004408.html
>>> but it only makes a difference if we export Fc to seaice_growth.
>>>
>>> I am going to add this option (to update F_ia using linearized approximation)
>>> in case one day we want to improve seaice_growth.
>>>
>>> Cheers,
>>> Jean-Michel
>>>
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