[MITgcm-support] Low salinity bias in PI experiment based on cpl_aim+ocn

[ht]

> Dear MITgcm Support Community,
>
> I am running coupled atmosphere–land–ocean experiments based on the cpl_aim+ocn configuration.
> My goal is to validate the model setup using a fully coupled PI-type experiment without SST/SSS relaxation or prescribed surface fluxes, before proceeding to paleoclimate simulations. The experiment is conducted with aim_fixed_pCO2 = 285e-6, following a PI control configuration.
>
> As the simulation progresses (after about 500 years), some parts of the ocean (e.g., the Southern Ocean and the Mediterranean Sea) become unrealistically fresh, as shown in the attached figure, and North Atlantic Deep Water (NADW) formation appears to cease.
>
> I would appreciate guidance on the following points:
>
> -
>
> Are there known issues or common pitfalls in cpl_aim+ocn that could lead to excessive ocean freshening?
>
> -
>
> In PI-control fully coupled experiments, is some form of SST/SSS relaxation generally required to maintain stable NADW formation?
>
> -
>
> When SST/SSS relaxation is turned off, are there specific parameters in data.land and/or data.aimphys that should be adjusted to avoid such behavior?
>
> Any suggestions on likely causes, useful diagnostics, or where to focus debugging efforts would be greatly appreciated.
>
> Thank you very much for your time and support.
>
> Best regards,
> Fisher
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://mailman.mitgcm.org/pipermail/mitgcm-support/attachments/20260115/a2368b4f/attachment-0001.html>
-------------- next part --------------
An embedded and charset-unspecified text was scrubbed...
Name: input_atm_data.land.txt
URL: <http://mailman.mitgcm.org/pipermail/mitgcm-support/attachments/20260115/a2368b4f/attachment-0007.txt>
-------------- next part --------------
An embedded and charset-unspecified text was scrubbed...
Name: input_atm_data.cpl.txt
URL: <http://mailman.mitgcm.org/pipermail/mitgcm-support/attachments/20260115/a2368b4f/attachment-0008.txt>
-------------- next part --------------
An embedded and charset-unspecified text was scrubbed...
Name: input_ocn_data.txt
URL: <http://mailman.mitgcm.org/pipermail/mitgcm-support/attachments/20260115/a2368b4f/attachment-0009.txt>
-------------- next part --------------
An embedded and charset-unspecified text was scrubbed...
Name: input_ocn_data.cpl.txt
URL: <http://mailman.mitgcm.org/pipermail/mitgcm-support/attachments/20260115/a2368b4f/attachment-0010.txt>
-------------- next part --------------
An embedded and charset-unspecified text was scrubbed...
Name: input_atm_data.aimphys.txt
URL: <http://mailman.mitgcm.org/pipermail/mitgcm-support/attachments/20260115/a2368b4f/attachment-0011.txt>
-------------- next part --------------
A non-text attachment was scrubbed...
Name: Mxld_500yr.png
Type: image/png
Size: 36391 bytes
Desc: not available
URL: <http://mailman.mitgcm.org/pipermail/mitgcm-support/attachments/20260115/a2368b4f/attachment-0002.png>
-------------- next part --------------
An embedded and charset-unspecified text was scrubbed...
Name: input_atm_data.txt
URL: <http://mailman.mitgcm.org/pipermail/mitgcm-support/attachments/20260115/a2368b4f/attachment-0012.txt>
-------------- next part --------------
An embedded and charset-unspecified text was scrubbed...
Name: input_cpl_data.cpl.txt
URL: <http://mailman.mitgcm.org/pipermail/mitgcm-support/attachments/20260115/a2368b4f/attachment-0013.txt>
-------------- next part --------------
A non-text attachment was scrubbed...
Name: SSS_500yr.png
Type: image/png
Size: 154372 bytes
Desc: not available
URL: <http://mailman.mitgcm.org/pipermail/mitgcm-support/attachments/20260115/a2368b4f/attachment-0003.png>