[MITgcm-support] Passive tracer decoupling from convection

[Yuxin Zhou]

Dear Christoph,
Your suggestions make a lot of sense. Thanks for pointing them out!

Cheers,
Yuxin

On Fri, Sep 3, 2021 at 1:52 AM Christoph Voelker <christoph.voelker at awi.de>
wrote:

> Dear Yuxin,
>
> in both of your setups I would not expect much response in the deep
> oxygen. In the first, AMOC recovers probably quickly, so there is not much
> reason to change. In the second, ten years is still fairly short, for
> changing tracer distributions in the deeper parts of the ocean. The
> timescale of ventilation of intermediate waters is on the order of several
> decades, in the deep ocean it is centuries to millenia. So I expect yo will
> at least have to run 1000 years with continuously changed overtrning to see
> some larger effects in the deep North Atlantic. Maybe have a look at the
> distribution of CFCs or anthropogenic carbon in the North Atlantic from the
> GLODAP data base; then you see observations of how far a signal from the
> surface penetrates within the deep Atlantic within a few decades.
>
> Cheers, Christoph
> Am 03.09.21 um 02:45 schrieb Yuxin Zhou:
>
> Hi Spencer,
> Thanks for the reply. I tested out two of your ideas. After hosing for one
> year, I first let the AMOC recover for 100 years. Oxygen basically remained
> the same. Then I hosed with 5Sv of freshwater for ten years. AMOC is
> basically gone at this point:
> [image: image.png]
>
> However, oxygen still didn't change much:
> [image: image.png]
>
> Going forward, I might test out the different advection schemes and other
> ptracer parameters to see if that helps. Again, I appreciate your help.
>
> Best,
> Yuxin
>
> On Wed, Sep 1, 2021 at 10:29 PM Spencer Jones <spencerjones at tamu.edu>
> wrote:
>
>> 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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>>>
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>
>
> --
> Yuxin Zhou
> https://www.ldeo.columbia.edu/~yzhou/
>
> _______________________________________________
> MITgcm-support mailing listMITgcm-support at mitgcm.orghttp://mailman.mitgcm.org/mailman/listinfo/mitgcm-support
>
> --
> Christoph Voelker
> Alfred Wegener Institute
> Helmholtz Centre for Polar and Marine Research
> Am Handelshafen 12
> 27570 Bremerhaven, Germany
> e: Christoph.Voelker at awi.de
> t: +49 471 4831 1848
>
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-- 
Yuxin Zhou
https://www.ldeo.columbia.edu/~yzhou/
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