[MITgcm-support] Inconsistent freshwater fluxes in/out of ocean+seaice

[Martin Losch]

Katy,

I am not sure, if I understand what you want to diagnose, but as far as I know, oceFWflx is the freshwater flux into the ocean (positive downward), while SIatmFW tries to diagnose the freshwater flux out of the atmosphere. Since there can be sea ice between atmosphere and ocean, this fresh water does not necessarily enter the ocean directly. Don’t nail me down on the sign conventions, but I think that their
SIatmFW - oceFWflx should give you the net freshwater flux into (out of?) the ice. That should be the same as the variations in ice volume (HEFF), but due to subteties in the timestepping and diagnostics output that may not always be the case. 

I think there is an example of what to diagnose to do it properly in verification/global_ocean.cs32x15/input.seaice/data.diagnostics, but I am also attaching a data.diagnostics and a matlab script that I once used to check the conservation properties (of seaice).

Martin


On Feb 4, 2014, at 9:57 PM, Katherine Quinn <kquinn at aer.com> wrote:

> Hi all,
> 
> I've noticed an inconsistency in the combined ocean and seaice freshwater mass variations when calculated two different ways (ignoring constant offsets).  The first method is sIceLoad (mass load of seaice) plus the cumulative in time sum of oceFWflx (flux in/out of ocean).  The second method is the cumulative in time sum of SIatmFW (flux in/out of ocean+seaice).
> 
> I've done these calculations using the diagnostic outputs of the latest MIT ECCO run (version 4, rev 4, iteration 10).  The seasonal cycle amplitudes and phases are off.  FYI, these are spatial averages (i.e. total mass) so lateral advection is not an issue.
> 
> Any insights appreciated.
> 
> cheers, Katy
> 
> -- 
> Katherine J. Quinn
> Atmospheric and Environmental Research         voice: 781-761-2234
> 131 Hartwell Avenue                              fax: 781-761-2299
> Lexington, MA  02421-3126                     e-mail: kquinn at aer.com
> 
> 
> 
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