The Indo-Pacific Throughflow is a part of the world conveyer belt circulation (downwelling in the North Atlantic, upwelling in the North Pacific and Indian Ocean). The connecting channel between the Pacific and the Indian Ocean is the Banda Sea and Makassar Strait. The conveyer belt and thus the Indo-Pacific Throughflow works only if there is downwelling in the North Atlantic. This occurs because of the net fresh water loss in the Atlantic compared with net fresh water gain in the Pacific. Only when the North Atlantic is added the conveyer belt circulation and thus upper and deeper ocean currents can build up meaningful flow patterns. With Indo-Pacific ocean model missing physical mechanism to attract mass in the Indic ocean leads to lower estimate of Indonasian Throughflow and the distorted flow in the Indonasian seas. Adding the North Atlantic would provided such mechanism of deep water formation in the Atlantic.
Gordon [1986] hypothesized that transport between the Pacific and Indian Oceans is an important component of global thermohaline circulation associated with the formation of North Atlantic Deep Water (NADW). Piola and Gordon [1984, 1986] examined the fresh water balance in the upper layer of the Pacific and Indian Oceans by means of mass and salinity conservation arguments in simple advective box model, suggesting that a flow of 14 Sv at 33.6 permille salinity into the Indian Ocean through the Southeast Asian Seas is required. By computing dynamic height Wyrtki [1987] showed that the flow of water from the western Pacific to the eastern Indian Ocean through the Indonesian seas is governed by a strong pressure gradient contained in the upper 200 m, and estimated the volume transport to be 1.7 Sv. He also showed that the annual signal has a maximum during the southeast monsoon in July and August and a minimum in January and February. Based on Sverdrup interior flow and geostrophy of longshore flow along western boundary currents, Godfry [1989] proposed a simple rule to calculate the depth-integrated steric height and stream fucntion at the inshore edge of western boundary currents. The observed differnce in annual mean steric height from western Australia to Indonesia suggested a Pacific-Indian Ocean throughflow of about 12 Sv. Fine [1985] showed direct evidence that there is a net transport, in the upper 300m, of 5 Sv from the Pacific to the Indian Ocean, using a meridional maximum in bomb-produced tritium observed in the South Equatorial Current (SEC) of the Indian Ocean.
In recent years, the waters in the western bounday of the tropical Pacific Ocean have received considerable attention in modeling potential significance of the Indonesian Throughflow not only to the Indian Ocean circulation [Godfrey and Golding, 1981], but also to the heat and salt balance of the Indian ocean [Godfrey and Ridgway, 1985] and in the world ocean [Gordon, 1986; Tool 1987].
Cox [1975] presnted the first systematic study of the role of baroclinicity in the circulation of the world ocean, in which the complete quasi-static dynamical equations are used to predict the velocity and density distributions. He used 2
