POP namelist variables that are controlled by XML

[mnlevy1981]

Description of the issue:

There are several variables in POP that the user should not be able to change via user_nl_pop, and many of them are ecosystem-related.

Low-hanging fruit:

 abio_dic_dic14_on
 cfc_on
 ciso_on
 ecosys_on
 iage_on
 irf_on
 sf6_on

are all set according to what's in OCN_TRACER_MODULES

@klindsay28 expanded the list with

Here are some (probably more to come later): chl_option depends upon OCN_CHL_TYPE lactive_ice depends upon OCN_ICE_FORCING atm_co2_opt depends upon OCN_CO2_TYPE lvariable_PtoC will depend upon OCN_TRACER_MODULES_OPT

This is not just a MARBL driver issue, so I'm not applying any labels

Version:

• CESM: 2.2
• POP2: cesm_pop_2_1_20190410
• Migrating from marbl-ecosys/MARBL#130, originally noted in January 2017 and assigned to @mvertens because at the time she was working on a python-based build-namelist script. I'm not assigning her this ticket because I don't believe that work has continued.

Machine/Environment Description:

Machine independent

Any xml/namelist changes or SourceMods:

Problem exists out of the box