The ocean component of the CESM2 is the Parallel Ocean Program version 2 (POP2).
This model is based on the POP version 2.1 of the Los Alamos National Laboratory; however, it includes many physical and software developments incorporated by the members of the Ocean Model Working Group detailed in the CESM2 Release Series Information page.
New Ocean Component
A new ocean component model based on the Modular Ocean Model version 6 (MOM6) has been incorporated into CESM and is anticipated to replace POP2 as the default ocean component in CESM3. An early functional release of the MOM6 ocean component is being made available to users beginning with CESM2.2. Instructions for using MOM6 in CESM are available on the MOM_interface Github Wiki page.