The difference drives upper thermocline water "downhill" through the deep, straight, westerly, north–south Makassar Strait then to meet the in reality combined Java Sea-Banda Sea.
Weaker flows of saltier and denser South Pacific slightly augment the Banda Sea via the Lifamatola Passage, both inflows mixing there due to its bounds and tides, Ekman pumping, and heat and freshwater flux.
From 2004 to 2006, 11 moorings were deployed across the entrance and exit regions of the ITF and were positioned to accurately measure each passage's contribution as part of the International Nusantara Stratification and Transport (INSTANT) program.
During monsoon transitions, strong westerly winds in the eastern Indian Ocean force equatorial downwelling Kelvin waves (eastward moving, eastward flow) that propagate through the Indonesian passages as coastally trapped Kelvin waves and serve to reduce the ITF flow with a minimum in April of 9 Sv.
[5] Western-central Pacific westerly winds from El Nino force westward moving-equatorial Rossby waves and eastward currents that hit eastern New Guinea and propagate around the west coast as coastal Kelvin waves and down through the ITF along the west Australia Shelf coast serving to reduce the ITF.
Interannual variability of Indian Ocean westerlies acts in the same manner as the seasonal equatorial Kelvin waves to reduce the normal westward ITF flow as well.