Improve isotope tracer flexibility and output variables #1093
Description
Summary
To support development of the next-generation water isotope–enabled CESM (iCESM), parts of
the isotope code in CICE should be updated to (1) allow flexible tracer configuration and (2)
standardize output variables.
Motivation
The current implementation relies on a fixed ordering and a limited set of isotope tracers. This
hard-coding makes it difficult to add new tracers, maintain consistency across model
components, and meet standardized diagnostic requirements.
Updates needed
- Flexible isotope tracer handling
Allow the model to run any set of isotope tracers (e.g., H₂¹⁸O, HDO, H₂¹⁷O) without index-
based assumptions. Key updates include: (1) Remove assumptions about tracer number and
ordering, (2) Replace index-based logic with a tracer/metadata configuration, and (3) Enable
tracers through the namelist or xml change.
- Rename isotope variables
Rename water-isotope output variables in CICE to align them with iCESM output conventions.