Petter, the MITgcm domain is doubly periodic. So you need a wall on at least one side of your domain to define a channel. Dimitris -- Dimitris Menemenlis <menemenlis at jpl.nasa.gov> Jet Propulsion Lab, California Institute of Technology MS 300-323, 4800 Oak Grove Dr, Pasadena CA 91109-8099 tel: 818-354-1656; fax: 818-393-6720