[MITgcm-support] Passive tracer decoupling from convection

[Spencer Jones]

Dear Yuxin,
It seems to me that maybe you just didn't run for long enough to see any
change in the oxygen concentration. From your email it seems like you only
ran for 1 year. Is that right? I wouldn't expect the oxygen concentration
to change until several years (maybe even decades) after hosing has taken
place, and only to change if the reduction in the AMOC continues (i.e. you
might want to continue hosing, rather than switching it off).

I'm not sure why tutorial_global_oce_biogeo doesn't match with
observations, but usually the tutorial experiments are set up to
demonstrate the model functionality, not to provide a very realistic
simulation. You might need to put more work into improving the forcing
fields and/or resolution in order to get realistic output.
Good luck ,
Spencer

On Tue, Aug 31, 2021 at 9:28 PM Yuxin Zhou <yzhou at ldeo.columbia.edu> wrote:

> Hi all,
> I'm running the tutorial_global_oce_biogeo experiment and analyzing the
> oxygen results and I found some weird behaviors. Any help would be
> appreciated.
>
> Here is the AMOC stream function in equilibrium, which looks normal:
> [image: image.png]
>
> Here is the AMOC stream function after a hosing of 5 Sv for one year
> (by increasing precipitation in the 50-70N North Atlantic region), which
> looks normal too. It shows a weakened NADW:
> [image: image.png]
>
> Here is the oxygen concentration of the AMOC cross-section in equilibrium:
> [image: image.png]
>
> Here is the oxygen concentration after the hosing:
> [image: image.png]
>
> Firstly, the oxygen concentration of the AMOC in equilibrium does not
> reflect modern observations such as the World Ocean Atlas, which shows
> oxygenated water closely following the presence of the NADW. Secondly,
> oxygen basically doesn't change even though circulation changed
> dramatically. It seems convection processes barely impact oxygen at all.
>
> Has anyone else seen this behavior? Any suggestions for tests I can run to
> figure out what's wrong?
>
> Thanks,
> Yuxin
> --
> Yuxin Zhou
> https://www.ldeo.columbia.edu/~yzhou/
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