[MITgcm-support] Query regarding BLING

[Matthew Mazloff]

Hi Kunal

I just looked more carefully and see you have undef SOLVESAPHE
However I don’t understand your plots. Top left and right panels are the exact same. Are those both DIC for the two runs.
These are also different times by 9 months which makes it hard to compare - Salt is super different.


Anyway, here is what I think is happening.
I added code:

cmm - rare, but ice melt can cause prescribed silicate alkalinity to be
cmm   larger than total alkalinity. Crop here to account for this
        IF (siooh3g.GT.0.2 _d 0*ta) siooh3g = 0.2 _d 0*ta
cmick - now estimate carbonate alkalinity
        cag = ta - bohg - (kwlocal/hguess) + hguess
     &           - hpo4g - 2.0 _d 0*po4g + h3po4g
     &           - siooh3g
CMM(
        IF ( cag .LT. (0.1 _d 0*ta) )  THEN
       print *,'CMMcag1', cag,i,j,k,xC(i,j,1,1),yC(i,j,1,1)
C myXGlobalLo-1+(bi-1)*sNx+i,        myYGlobalLo-1+(bj-1)*sNy+j
       print *,'CMMcag2',ta,bohg,(kwlocal/hguess),hguess,hpo4g,
     &           2.0 _d 0*po4g,h3po4g, siooh3g
       cag = 0.1 _d 0*ta
        ENDIF
CMM)

When one inputs fresh water it dilutes alk and should dilute silica but we are prescribing silica and it doesn’t drop.  This can make carbonate alkalinity go negative and blow up the carbon system. I put caps here to assume silicate alk is always less than 20% of total and to assume carbonate alkalinity can’t go lower than 10% of total alkalinity. 
This keeps the carbon system stable, but perhaps for your case causes spurious results. Maybe these caps are too strong. 

I notice you give different silica files for DIC and BLING. Maybe you are giving a low enough silica to DIC to keep it stable but high enough to BLING to set off these caps. 

You could try commenting out 
        IF (siooh3g.GT.0.2 _d 0*ta) siooh3g = 0.2 _d 0*ta
…
CMM(
        IF ( cag .LT. (0.1 _d 0*ta) )  THEN
       print *,'CMMcag1', cag,i,j,k,xC(i,j,1,1),yC(i,j,1,1)
C myXGlobalLo-1+(bi-1)*sNx+i,        myYGlobalLo-1+(bj-1)*sNy+j
       print *,'CMMcag2',ta,bohg,(kwlocal/hguess),hguess,hpo4g,
     &           2.0 _d 0*po4g,h3po4g, siooh3g
       cag = 0.1 _d 0*ta
        ENDIF
CMM)

in bling_carbon_chem.F
and see if it is then the same as DIC

(I also put caps on the range of pH so this may end up kicking in and keeping the model stable if needed)

I can try to help further but to do so it would be good to see ALK, Salt, Silica, and pH all for the same timestep, and ideally early in the run when DIC and BLING first diverge.

Matt




> On Sep 25, 2023, at 6:58 AM, kunal madkaiker <kunal.madkaiker02 at gmail.com> wrote:
> 
> Hi all,
> 
> I have some issues resolving the carbon chemistry using the BLING package. My domain has river runoff included as a point source. When using the 'DIC' package, DIC and ALK conc. get diluted causing pH to increase at those points (which is correct).
> 
> However, when I use the same setup with the BLING package, the DIC and ALK conc. are getting diluted but the pH decreases rapidly (5-6 pH).
> 
> Secondly, has the SOLVESAPHE algorithm been fully implemented in BLING or not yet? I tried defining 'CARBONCHEM_SOLVESAPHE' in BLING_OPTIONS.h and 'selectpHsolver=1' in data.bling but then I got the segmentation error. Otherwise, it works fine.
> 
> Let me know what you think. I am attaching the required files and plots for your reference.
> 
> Thanks,
> Kunal
> <BLING_OPTIONS.h><DIC_OPTIONS.h><data.dic><data.bling><sterr_file><using_bling.gif><using_dic.gif>_______________________________________________
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