[MITgcm-support] Closing DIC budget

[Wenrui Jiang]

Dear MITgcm support group,

Thanks for reading this. My name is Wenrui Jiang, and I am a PhD student from Johns Hopkins. I want to apologize in advance for my inexperience.

I am trying to close the DIC budget on the biogeochemical tutorial example (https://mitgcm.readthedocs.io/en/latest/examples/global_oce_biogeo/global_oce_biogeo.html). The diagnostics that I include are:

TRAC01  |SMR     MR|mol/m^3         |Dissolved Inorganic Carbon (DIC) [mol C/m^3] concentration
ForcTr01|SMR     MR|mol/m^3/s       |DIC forcing tendency
AB_gTr01|SMR     MR|mol/m^3/s       |DIC tendency from Adams-Bashforth
Tp_gTr01|SMR     MR|mol/m^3/s       |DIC total transport tendency (before gchem_forcing_sep)
ADVrTr01|WM      LR|mol/m^3.m^3/s   |Vertical   Advective Flux of DIC
ADVxTr01|UU      MR|mol/m^3.m^3/s   |Zonal      Advective Flux of DIC
ADVyTr01|VV      MR|mol/m^3.m^3/s   |Meridional Advective Flux of DIC
DFrETr01|WM      LR|mol/m^3.m^3/s   |Vertical Diffusive Flux of DIC (Explicit part)
DFxETr01|UU      MR|mol/m^3.m^3/s   |Zonal      Diffusive Flux of DIC
DFyETr01|VV      MR|mol/m^3.m^3/s   |Meridional Diffusive Flux of DIC
DFrITr01|WM      LR|mol/m^3.m^3/s   |Vertical Diffusive Flux of DIC (Implicit part)

DICBIOA | 15 |SM P    MR      |mol/m3/sec      |Biological Productivity (mol/m3/s)
DICCARB | 15 |SM P    MR      |mol eq/m3/sec   |Carbonate chg-biol prod and remin (mol eq/m3/s)
DICTFLX |  1 |SM P    L1      |mol/m3/sec      |Tendency of DIC due to air-sea exch (mol/m3/s

So far, I managed to close the Tp_gTr01 term with the advective and diffusive flux in the interior to machine precision. However, at the surface there is a large residual, which I am not able to close with ForcTR01. I am wondering if this is a dilution effect from PTRACER_ref.

I am also having a hard time matching Tp_gTr01 and the tendency diagnosed from DIC and Eta snapshots using the GCHEM diagnostics. The GCHEM diagnostics seems to have very small value (10^-10 mol/m^3/s) which is much smalller than the difference.

I would really appreciate it if you could tell me whether:

  1. I am using the correct diagnostics in the correct way;
  2.there are any model setups that prevent a tracer closure.

Thank you very much!

Sincerely,
Wenrui

Wenrui Jiang

Ph.D. Student,
Department of Earth & Planetary Sciences,
Johns Hopkins University.

Email: wjiang33 at jh.edu

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