[MITgcm-support] separating sea ice and atmos FW fluxes

[Holland, Paul R.]

Hi Martin,

You're right, the DV/Dt thing was the result of a catastrophic misunderstanding of your earlier mail on my part.  I will calculate IO = SIdHbOCN+SIdSbOCN+SIdHbATO and AO=SIempmr-IO.

Thanks for your wisdom,

Paul

-----Original Message-----
From: Martin Losch [mailto:Martin.Losch at awi.de]
Sent: 17 February 2015 17:29
To: MITgcm Support
Subject: Re: [MITgcm-support] separating sea ice and atmos FW fluxes

Hi Paul,

I think what you need is option (2): IO = SIdHbOCN+SIdSbOCN+SIdHbATO SIdSbOCN is likely to be zero, but not always.

why would you want DV/DT? all of these diagnostics are from within seaice_growth and accumulate (if used as averages) the “thermodynamic” growth. Advection is independent (algorithmically) would only redistribute ice and snow.

I don’t thing that your (3) is possible. Please refer to seaice_growth:
C and the flux leaving/entering the ocean+ice
           SIatmFW(I,J,bi,bj) = maskC(I,J,kSurface,bi,bj)*(
     &          EVAP(I,J,bi,bj)*( ONE - AREApreTH(I,J) )
     &          - PRECIP(I,J,bi,bj)
     &          - RUNOFF(I,J,bi,bj)
     &           )*rhoConstFresh
     &     + a_FWbySublim(I,J) * SEAICE_rhoIce * recip_deltaTtherm
Because of “AREApreTH” you will probably not be able to back out AO without having extra diagnostics, so I would go with option (2).

Martin

> On 17 Feb 2015, at 11:30, Holland, Paul R. <pahol at bas.ac.uk> wrote:
>
> Thanks Martin,
>
> Very helpful but I think this time my confusion might be terminal.  So a few follow-up questions...
>
> 1) I think if I wanted to back out AI-IO (using the notation of my
> original email) I would need to combine those 5 with the ice advection
> terms to get DV/Dt (rather than dV/dt)?  That does not sound like the
> secret to a long and happy life :)
>
> 2) It sounds as if I could just calculate IO directly from the sum of SIdHbOCN, SIdSbOCN, SIdHbATO?  That sounds better.
>
> 3) Are you sure there isn't an even simpler way, e.g. to get AO by differencing some EXF diagnostic from SIatmFW to see what the sea ice has done to the flux out of the atmosphere?
>
> cheers
>
> Paul
>
> -----Original Message-----
> From: Martin Losch [mailto:Martin.Losch at awi.de]
> Sent: 17 February 2015 13:57
> To: MITgcm Support
> Subject: Re: [MITgcm-support] separating sea ice and atmos FW fluxes
>
> Hi Paul,
>
> I think these are the relevant diagnostics for DV/DT (without the advection which, presumably, you don’t want):
>      diagName  = 'SIdHbOCN'
>      diagTitle = 'HEFF rate of change by ocean ice flux'
>
>      diagName  = 'SIdSbATC'
>      diagTitle = 'HSNOW rate of change by atm flux over sea ice'
>
>      diagName  = 'SIdSbOCN'
>      diagTitle = 'HSNOW rate of change by ocean ice flux'
>
>      diagName  = 'SIdHbATC'
>      diagTitle = 'HEFF rate of change by atm flux over sea ice'
>
>      diagName  = 'SIdHbATO'
>      diagTitle = 'HEFF rate of change by open ocn atm flux’
> all in meters of sea ice per second. Could it be easier than that? (;
>
> Martin
>
>
>> On 17 Feb 2015, at 04:15, Holland, Paul R. <pahol at bas.ac.uk> wrote:
>>
>> Dear listees
>>
>> I'm sorry but I'm getting confused with sea ice freshwater diagnostics... again!  I want to work out how much of the freshwater going into the ocean comes from sea ice, P-E, runoff, and ice shelves.  It's the first two I have problems with.
>>
>> From previous threads I know that SIempmr is the total FW flux into the ocean, and SIatmFW is the total FW leaving the atmosphere.  However, I want the net FW flux into the ocean from ice melt, and the net P-E into the ocean through leads in the ice.  I can't work out how to derive that from these two diagnostics.
>>
>> The way I see it, there are three relevant fluxes:
>>
>> AI: atmophere->ice FW flux
>> AO: atmosphere->ocean FW flux
>> IO: ice->ocean FW flux
>>
>> SIempmr=IO+AO, while SIatmFW=AI+AO.  I want IO and AO, so I am trying to solve a system of 2 equations with 3 unknowns!  Can someone tell me where I am going wrong, or provide me with one or more diagnostics that will unlock the system?  If I had the change in total ice mass DV/Dt=AI-IO that would do it, but I don't fancy trying to calculate the material derivative.
>>
>> Hopefully I'm just confused.
>>
>> cheers,
>>
>> Paul
>>
>> Dr. Paul Holland
>> British Antarctic Survey
>> p.holland at bas.ac.uk
>> +44 (0) 1223 221444
>> http://www.antarctica.ac.uk/profile/paul
>>
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