Velocity structure and transport of the Indonesian Throughflow in the major straits restricting flow into the Indian Ocean

An array of shallow pressure gauge pairs is used to determine shallow geost rophic flow relative to an unknown mean velocity in the five principal stra its that separate the eastern Indian Ocean from the interior Indonesian sea s (Lombok Strait, Sumba Strait, Ombai Strait, Savu/Dao Straits, and Timor P assage). Repeat transects across the straits over several tidal cycles with a 150-kHz acoustic Doppler current profiler were made during three separat e years, and provide a first look at the lateral and vertical structure of the upper throughflow in these straits as well as a means of "leveling" the pressure gauge data to determine the mean shallow velocity and provide tra nsport estimates. We estimate a total 2-year average transport for 1996-199 7 through Lombok, Ombai, and Timor Straits as 8.4 +/- 3.4 Sv toward the Ind ian Ocean. The flow structure in the upper 200 m is seen to be similar in L ombok, Sumba, and Ombai Straits, with a division into two layers, governed by different dynamics, where the upper layer episodically flows away from t he Indian Ocean. Laterally, flow tends to be strongest in the deepest parts of the channel, with the exception of Lombok Strait which shows a consiste nt intensification of flow toward the western side. Eastward flowing northe rn boundary currents in Sumba and Ombai Straits suggest that the South Java Current may penetrate to the Banda Sea, farther eastward than previously d ocumented. Although additional observations are required for a conclusive c omparison, the estimated transport time series suggest differences in timin g of outflow into the Indian Ocean relative to inflow from the Pacific of a size that could significantly impact the Banda Sea thermocline structure.