[MITgcm-devel] seaice_solve4temp.F cleaning update

[Jean-Michel Campin]

Hi Ian,

On Thu, Feb 02, 2012 at 09:18:38PM -0800, Ian Fenty wrote:
> 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
I can follow until this point.

> T_ice(surface) < T_ice(base) - 
And then I am lost. If you take my 1rst message, (which has not been copied 
here below), I put a simple example with number and conventions.

> then F_c represents conducting heat
> away from the surface not, down the monotonic gradient, towards the
Hard to follow (not down the monotonic gradient ?)

> 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?
Yes, it's what I wanted to illustrate.

Cheers,
Jean-Michel
> 
> -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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> 
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