Neogene history of the Indonesian Throughflow

The Indonesian Throughflow acts as a major switchboard in the global thermohaline circulation, and its variability is strongly related to tropical climate dynamics on shorter and longer timescales. During the Holocene and Pleistocene, fluctuating sea surface temperature and salinity patterns in the Western Pacific Warm Water Pool and Indonesian Seas and variations in East Asian monsoon strength mainly controlled the intensity and hydrological characteristics of the throughflow. Additionally, glacial/deglacial sea-level change strongly influenced throughflow volume in shallow sections of many passages (i.e. the southern part of the Timor passage on the NW Australian shallow shelf) thus altering the related heat transfer between oceans. The tectonic history of the Indonesian Gateway ultimately controlled the long-term evolution of the throughflow. During the Pliocene, changes in the position and geometry of the inflow passages (Mindanao Passage to the North and Halmahera Passage to the south) in relation to the tropical Pacific front significantly modified the climatic role of the tropical Indian and Pacific Oceans, resulting in reduced atmospheric heat transport from the tropics to high latitudes. However, the precise timing of major restriction in the surface and thermocline water flow is difficult to ascertain. The early evolution of the Indonesian Gateway was characterized by tectonic restriction of the deep water pathway between the Pacific and Indian Oceans at approximately 25 Ma. By the early Miocene, the Indonesian Gateway was already closed as a deep water pathway between the Pacific and Indian Oceans.