An empirical search procedure based only on hydrographic data and the use of the dynamical method provides a good estimate of the level of no motion. The criterion is to select the level that yields the minimum mean square transport imbalances for the set of carefully chosen independent layers....
Fiadeiro, Manuel E., and George Veronis. 1982. "On the determination of absolute velocities in the ocean." Journal of Marine Research 40, (S). https://elischolar.library.yale.edu/journal_of_marine_research/1638