The Molucca Sea is an important passageway for deep water flowing from the Pacific Ocean through the Australasian Mediterranean and on into the Indian Ocean. One branch of flow through the Molucca is composed of deep flow from the Pacific through the Sangir Trough and on into the Sulawesi Sea, while another branch has flow entering via the Morotai Basin and exiting via the Gorontalo Basin south of Sulawesia as well as through the Lifamatola Strait into the Banda and Ceram Seas. Surface salinities depart at most 0.3 from an annual average of 34.0, although higher salinities have been recorded late in the year in the north and southern extremities. The surface salinities range from 28.3 C in June to 27.0 C in January.
The monsoon winds drive the surface circulation, changing slowly in direction from northeast to north-northwest during the southern summer and generally reversing direction during the winter months. As such a slow current flows southwestward along the eastern margin of the sea along with an opposite (northward) flowing current of similar strength in the western half in the winter months. The northward flow is maintained throughout the year except in the northern reaches where an east-southeast directed current occurs in the summer months. See Fairbridge (1966).
where g is gravitational acceleration, z the vertical coordinate, T temperature and the specific heat at constant pressure.