thank you for making this PR @owang01 ! i left a couple of comments in ecco_phys.F. I think it'd be great to leave a reference for how you computed the freeboard, e.g., derived from the equation for "lidar" from this Kwok & Markus, 2018 manuscript https://www.sciencedirect.com/science/article/abs/pii/S0273117717306403?via%3Dihub .

other than this and the potential division by zero--i think there should be a check somewhere in case user set the SEAICE_area_reg = 0. _d 0 ? perhaps there is already such a check in pkg/seaice that i miss?

also, i didn't check.. but are there different treatments if you're using the various levels of nonlinFreesurf [0-4] ? and/or with/without RFWF?

also, i didn't check.. but are there different treatments if you're using the various levels of nonlinFreesurf [0-4] ? and/or with/without RFWF?

Just to clarify: the Sea-ice freeboard expression here is intended to be compared with obs and is independent of internal model assumptions (including free-surface).

also, i didn't check.. but are there different treatments if you're using the various levels of nonlinFreesurf [0-4] ? and/or with/without RFWF?

Just to clarify: the Sea-ice freeboard expression here is intended to be compared with obs and is independent of internal model assumptions (including free-surface).

thanks Jean-Michel. Yes, i think you verbally mentioned this at the last (last) devel meeting already, but good to confirm here for the record.

@antnguyen13 Thank you for your review. I have added comments on freeboard calculation and included Kwok and Markus (2018) as an example reference. I did not add a check for SEAICE_area_reg = 0._d 0, as it was deemed unnecessary based on discussions in one of the devel meetings.