[MITgcm-support] Surface forcing of ptracers...

[Gus Correa]

Hi Jody

In bling_airseaflux.F there is code for oxygen gas exchange based on the
Wanninkhof 1992 formula that is quadratic in windspeed (JGR, V.97, NO.
C5,pp. 7373-7382,
updated in Wanninkhof 2014 Limnology and Oceanography:Methods, 12, pp
351-362).

The gas exchange velocity (kwexch) dependency on the windspeed and on the
Schmidt number (Sc),
and the gas flux go like this:
kwexch = a * (Sc/660)^(-1/2) * windspeed^2, where Flux = kexch * [Ca - Cw]
where Ca and Cw are the oxygen concentration in the atmosphere and ocean.
The leading constant "a" depends on the wind product (see, e.g. Sweeney et
al. 2007, Global Geochemical Cycles,
v. 21, GB2015).

The bling code doesn't use the same Schmidt number coefficients given in
Wanninkhof 2014 (in bling_init_fixed.F)
and instead of using the Bunsen solubility of Wanninkhof 2014, it uses the
C*_o
solubility from Garcia and Gordon 1992 (Limnololgy and Oceanography, 37(6),
pp. 1307-1312).

The dependency on T and S is buried in the Schmidt Number, and in the
solubility.
Wanninkhof 1992 gives the Schmidt number as third order polynomial in T.
Garcia and Gordon provide another polynomial/logarithmic mixed formula for
the solubility as a function of T and S.

I hope this helps,
Gus Correa

On Sun, May 22, 2022 at 4:55 AM Jody Klymak <jklymak at uvic.ca> wrote:

> Dear Matt and Manfredi,
>
> Thanks to you both.  I think that is more than enough to point me in the
> right direction.
>
> Cheers Jody
>
> Sent from my iPhone
>
> On May 22, 2022, at 00:01, Manfredi Manizza <mmanizza at ucsd.edu> wrote:
>
> 
> Hi Jody,
>
> I think you could  look at code of the DIC package that comes with
> MITgcm.  You can either strip down the code to 1 tracer and
> also remove the routine of gas exchange for CO2 or  you can then just copy
> from that code  the routine for gas exchange of O2 with the  solubility and
> gas exchange parameters along that you need to make it work and re-adapt to
> your code.
>
> In the second case you might need gchem pkg too (is needed for dic pkg too
> I think) compiled to make it work. Then you add the gas exchange code
> and pass the flux term to your O2- like  tracer tendency only if  k = 1
> (surface ocean only).
>
> Here below  something similar to your case done a while ago where I added
> the "thermal oxygen"
> but still in the context of a  full bgc model.
>
> In that case I just copied the code of the oxygen cycle and removed the
> "sources minus sink" term so that it becomes "abiotic" only, like  that
> tracer you want to obtain for
> your study in the fjord if I understood correcly.
>
> https://www.tandfonline.com/doi/full/10.3402/tellusb.v64i0.18429
>
> I hope this helps.
>
> Manfredi
>
> On Sat, May 21, 2022 at 2:51 AM Jody Klymak <jklymak at uvic.ca> wrote:
>
>> Hi all,
>>
>> I am trying to add a crude oxygen signal to a wind and thermally forced
>> fjord simulation.  I don’t particularly need the oxygen to interact
>> bio-chemically with anything, but I assume it would be more realistic for
>> the gas exchange to depend on the wind speed and the surface oxygen
>> saturation (as a function of T and S).
>>
>> I am finding it a little difficult to parse how I might do that.  I don’t
>> see a surface forcing for ptracer.  It seems that maybe biochem has all
>> this, but its still not clear if I should use all this machinery and how to
>> initialize in an idealized sense.
>>
>> Any pointers gratefully received.
>>
>> Thanks a lot.   Jody
>>
>> --
>> Jody Klymak
>>
>> https://urldefense.proofpoint.com/v2/url?u=http-3A__ocean-2Dphysics.seos.uvic.ca_-7Ejklymak_&d=DwIGaQ&c=-35OiAkTchMrZOngvJPOeA&r=igpxhFyItwkD6Vnn8g54Ybzj3kX5f-S1LY9JKm2YT1c&m=nkgsUY2t8ODuPG_Q1j0WukX0YFM4WaWyWHEtpl4Irx0TBNMmMbHsGZcbi8hudusN&s=bZOGEPvGiJv1KgPp3U-2Hzz7Ze3F1qZ-g-DMbG019-8&e=
>>
>>
>>
>>
>>
>>
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>>
>
>
> --
>
> Dr. Manfredi Manizza
> Geosciences Research Division
> Scripps Institution of Oceanography
> University of California San Diego
> 9500 Gilman Drive La Jolla, CA 92093-0244
> email : mmanizza at ucsd.edu
> tel   : +1-858-534-7094
> web   : http://bluemoon.ucsd.edu/mmanizza/
>
> web   : https://mmanizza.scrippsprofiles.ucsd.edu/
>
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