The late Miocene to Pliocene constriction of the Indonesian Gateway and its impact on ocean circulation and climate

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Our studies focus on the Miocene to Pliocene closure of the Indonesian Gateway and its impact on changes in global ocean circulation and climate. The constriction of the Indonesian Gateway led to the formation of the modern W-Pacific warm water pool and changed ocean circulation from a predominantly latitudinal to a meridional flow. In particular, we will examine the progressive reduction of the Indonesian Throughflow within the time period from -8 to ~2.4 Ma and test the hypothesis of Cane and Molnar (2001) that the early Pliocene constriction of the Indonesian Gateway might have triggered the onset of the Northern Hemisphere Glaciation (NHG). According to general circulation models, the reduction in the Indonesian Throughflow should have led to (1) a surface cooling of the Indian Ocean, (2) a strengthened meridional heat transfer from the tropics to the Southern Ocean via an intensified East Australian Current, and (3) a weakening of the Leeuwin Current on the western side of Australia. Four DSDP/ODP Sites were selected to investigate these proposed changes: Site 756 (214) from the tropical east Indian Nürnberg/Tiedemann: Indonesian Gateway Ocean, Site 763 below the Leeuwin Current, and Sites 580 and 1172 within the influence of the East Australian Current. The combined measurement of planktic foraminiferal Mg/Ca and 51SO will allow to reconstruct sea-surface (subsurface) temperatures, thermocline depth and salinities at a temporal resolution for the Miocene/Pliocene time slice not yet available, and will allow to decipher hydrographic changes during the constriction of the Indonesian Throughflow.