| The Indonesian Throughflow (ITF), which transports approximately 15 Sv (1 Sv = 106 m3s-1) from the tropical Pacific Ocean into the Indian Ocean, is an important element in the heat and freshwater budgets of these oceans. The water transferred by the ITF is relatively cool and low in salinity compared to the Indian Ocean, and is an important link in global ocean circulation as the route by which warm water returns from the Pacific Ocean to the Atlantic Ocean, closing the loop of thermohaline overturning circulation. This dissertation examines the setting and forcings of the ITF on global, regional, and local scales. The ITF assimilates signals from El Nino-Southern Oscillation (ENSO), the Indian Ocean Dipole, and the Southeast Asian Monsoon, and responds with changes in total transport, transport profile, or temperature. A 50-year timeseries of the ITF transport variability is calculated using regional reanalysis data from the Simple Ocean Data Assimilation model. That timeseries is shown to accurately model the available in-situ data for the Makassar Strait at periods longer than nine months. ENSO is shown to affect both the surface and thermocline layers during major ENSO events, while in neutral periods the surface layer responds to local winds while the thermocline layer responds to more distant forcings from the Pacific and Indian Oceans. The island rule calculation, while useful in determining the magnitude of the ITF, does not correlate with this timeseries of ITF variability because it does not show a strong response to ENSO. Based on this timeseries, the internal energy transport (IET) of the ITF is 0.53 PW, with a transport-weighted temperature (TWT) of 14.6°C. The transport profile of the ITF varies with the total volume of the ITF, with increases in transport concentrated in the deeper, cooler layers. The IET and the TWT therefore do not co-vary, as the IET increases directly with increased transport while the TWT is lowered by the increased flow of cooler water. The IET is highly correlated with the NINO3.4 index and the depth of the western Pacific 18°C isotherm, but TWT is not. This suggests that the ENSO signal is transferred from the Pacific to the Indian Ocean primarily by changes in transport, not temperature. Based on this research, ideas for future research in physical oceanography and paleoceanography are proposed. |
