Abstract. An array of shallow pressure gauge pairs is used to determine shallow geostrophic flow relative to an unknown mean velocity in the five principal straits that separate the eastern Indian Ocean from the interior Indonesian seas (Lombok Strait, Sumba Strait, Ombai Strait, Savu/Dao Straits, and Timor Passage). Repeat transects across the straits over several tidal cycles with a 150-kHz acoustic Doppler current profiler were made during three separate 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 transport estimates. We estimate a total 2-year average transport for 1996-1997 through Lombok,

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Recent measurements from six bottom-mounted gauges are used with numerical model results to study the exchange of water between the Indonesian seas and the Indian Ocean via the Lesser Sunda Islands known collectively as Nusa Tengarra. The observations are approximately three years in length, from late 1995 to early 1999, and include measurements of bottom pressure, temperature, and salinity. The locations of the gauges are at the boundaries of three straits connecting the southern Indonesian seas with the eastern Indian Ocean: the Lombok Strait, the Ombai Strait, and the Timor Passage. The magnitude of intraseasonal variations in the pressure data dominates over that of the seasonal cycle. Intraseasonal variability appears most frequently and largest in magnitude at the westernmost strait (Lombok) and decreases along the coastline to the Timor Passage. Comparison to wind data shows these intraseasonal variations to be due to Kelvin wave activity in the Indian Ocean, forced by two distinct wind variations: semiannual monsoon reversals and Madden-Julian oscillation (MJO) activity. Sea level variations from both forcing mechanisms are then adjusted by local, alongshore winds. Longer-duration model results show the observation period (1996 through early 1999) to be a time of increased ENSO-related interannual variability and of suppressed annual cycle. MJO activity is also increased during this time. These factors explain the dominance of the higher frequency signals in the pressure data and the relative lack of a distinct annual cycle. An optimal fit of model sea level variations to model through-strait transport variations is used to estimate transport variability from the observed pressure records. At each strait the optimal fit is consistent with a cross-strait geostrophic balance for transport variations in the upper 250 m.

Abstract. Since December 1995, the Indonesian throughflow has been monitored in five major passages as it flows from the Indonesian interior seas to the Indian Ocean. Pressure differences across the straits enable us to infer the geostrophic surface flow, and so provide the first simultaneous time-series measurements of surface geostrophic flow through these passages. Intraseasonal signals (30-90 day) are a ubiquitous feature in the surface flow, and are consistent with wind-forced Kelvin waves from both the eastern equatorial Indian Ocean and the south coast of Java. Using a relationship with surface velocity from three contemporaneous ADCP surveys, we approximate surface (0-100 m) volume transport fluctuations through four of the main exit passages. The amplitude of the total surface transport variation through these passages is fairly uniform, ranging from 10-15 S v.