The isotope-enabled Community Earth System Model version 1.2 (iCESM1.2) iCESM1.2 is a version of NCAR's CESM1.2 with the ability to simulate water isotopes (HDO and H218O) through the entire modeled hydrologic cycle, along with the ability to simulate multiple different water tracers in the atmosphere (CAM5). Please note that this version MUST run with water isotopes. If you want a standard version of CESM1.2 then please find instructions for acquiring the non-isotopic CESM1.2 model online here: http://www.cesm.ucar.edu/models/cesm1.2/ If you are interested in water isotopes or water tracers, then instructions for running iCESM1.2 with those tracers can be found in the "instructions" directory included in this repository. Along with those instructions, a scientific description of iCESM1.2 itself can be found online here: https://agupubs.onlinelibrary.wiley.com/doi/full/10.1029/2019MS001663 or here: https://doi.org/10.1029/2019MS001663 Finally, if you have any questions or concerns regarding this model then please add a post to the CESM forums: https://xenforo.cgd.ucar.edu/cesm/ and an NCAR scientist or engineer will respond to your query promptly. Good luck!