Sea-ice activation inconsistency in SBC

[smueller]

Context

Analysis in the context of ticket #2403 revealed an inconsistency in the activation of sea-ice inclusion in the surface boundary condition (SBC) between model setups with and without AGRIF: when key_si3 is defined, sea-ice inclusion is activated irrespective of the value of namsbc namelist parameter nn_ice in AGRIF parent domains, whereas non-AGRIF configurations require the explicit setting of nn_ice to an appropriate value in order to include sea-ice in the SBC.

Analysis

When either key_si3 or key_cice is defined, the value of the nn_ice namelist parameter is overridden in parent AGRIF domains, but remains unmodified in non-AGRIF model configurations as well as in child AGRIF domains (lines 123-132 in source:/NEMO/trunk/src/OCE/SBC/sbcmod.F90@12489​). A discussion in the context of ticket #2403 confirmed that this override mechanism has been deliberately deactivated in child AGRIF domains and in non-AGRIF configurations (cf. [1242] and [12063], respectively) and suggested that it should be removed for parent AGRIF domains also.

Recommendation

The complete removal of lines 123-132 of source:/NEMO/trunk/src/OCE/SBC/sbcmod.F90@12489​ is recommended in order to remove the sea-ice activation inconsistency in SBC. In addition, the explicit setting of nn_ice = 2 in the namelists for the parent AGRIF domains in AGRIF-enabled configurations with sea ice in source:/NEMO/trunk/cfgs and source:/NEMO/trunk/tests should be verified. Further, comments that refer to the nn_ice override mechanism in some of the namelist files for the configurations in source:/NEMO/trunk/cfgs and source:/NEMO/trunk/tests should be adjusted to bring them in line with the actual implementation of the sea-ice activation mechanism in SBC.

[smueller]

In 12994:

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No macro or processor named 'CommitTicketReference' found

[smueller]

The recommendation has been implemented with [12994]. NEMO/trunk@12994 passes SETTE on two systems; SETTE results are unchanged with respect to NEMO/trunk@12925 and NEMO/trunk@12984, respectively.