[MITgcm-devel] recently added SHELFICEMassStepping in pkg/shelfice

[Jean-Michel Campin]

Hi Dan,

On Mon, Jan 12, 2015 at 10:52:13AM +0000, Daniel Goldberg wrote:
> Hi J-M
> 
> Sorry for taking so long to respond. I think my fault, actually, that I did
> not explain shelfIceMassDynTendency in SHELFICE.h. Also my hardcoded ice
> density was a bit of a hack, as I acknowledged in the comment. Agreed that,
> to be consistent with all else, the MassDynTendency should be in mass per
> unit area rather than elevation units. Also fine with the _RS to _RL
> conversion, of course.

No problem there, it's not urgent; but now that you & Martin agree, will 
proceed with these changes relatively soon.

> pkg/streamice has its own ice density parameter. how extensively is
> rhoShelfice used? Is it at all worth attempting to force consistency
> between the packages (e.g. by using a single parameter in PARAMS.h)?

This is a common issue with several components exchange fluxes; the way
we can be sure that we conserve key quantities is to exchange, e.g. mass per
unit area (per unit of time) instead of volume, heat flux in W/m^2
instead of temperature tendency ... each component should be able to make
its own budget (using its own assumptions for density and Cp) and
the system is conserving even with different assumptions across components.

Cheers,
Jean-Michel

> 
> Thanks
> Dan
> 
> On Fri, Jan 9, 2015 at 5:48 PM, Jean-Michel Campin <jmc at ocean.mit.edu>
> wrote:
> 
> > Hi Dan and Martin,
> >
> > regarding the newly added option "SHELFICEMassStepping"
> > and new S/R SHELFICE_STEP_ICEMASS:
> >
> > I realized that the units of forcing field array
> >  "shelfIceMassDynTendency" are not documented (in SHELFICE.h, partly my
> > fault),
> > and would like to change it from a thickness tendency contribution
> > to a mass tendency per unit area [kg/m^2/s], and taking
> > this opportunity to remove the hard coded "910." number
> > (which represents ice-shelf density, but is inconsitent with
> > pkg/shelfice parameter "rhoShelfIce").
> > Dan, are you OK with this modification ?
> >
> > An other minor thing: I am thinking of changing few field arrays
> > in pkg/shelfice (including shelficeMass, which can now be stepped forward)
> > from _RS to _RL ; this should have very little consequences since
> > almost nobody uses RS=real*4. I think that by upgrading few arrays
> > there from _RS to _RL I can get 1 cg2d matching digits (currently: zero
> > digits)
> > when I run testreport with -r4 option, see e.g.:
> > http://mitgcm.org/testing/results/2015_01/tr_danton_20150103_2/summary.txt
> >
> > Cheers,
> > Jean-Michel
> >
> >
> > _______________________________________________
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> > MITgcm-devel at mitgcm.org
> > http://mitgcm.org/mailman/listinfo/mitgcm-devel
> >
> 
> 
> 
> -- 
> 
> Daniel Goldberg, PhD
> Lecturer in Glaciology
> School of Geosciences, University of Edinburgh
> Geography Building, Drummond Street, Edinburgh EH8 9XP
> 
> 
> em: D <dgoldber at mit.edu>an.Goldberg at ed.ac.uk
> web: http://ocean.mit.edu/~dgoldberg

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