<![CDATA[An extreme upwelling event (EUE) off Alor Kecil (central Pantar Strait, Indonesia) can cause sea-surface temperature (SST) to drop by >10 °C within hours, indicating rising cold water from the deep basin. The EUE occurs along the Mulut Kumbang Strait, a narrow channel 300 m wide and 900 m long. Understanding the water-mass origin of the EUE may provide insights into the mechanism of EUE generation. Prior eDNA analyses suggested a deep-ocean source (Savu Sea Basin) based on the detection of bathypelagic fish genetic materials at the Mulut Kumbang Strait during the EUE, which indicates that the water-mass origin of the EUE may come from a depth of more than 1,000 m. To confirm the source of the cold-water mass, we present a multibeam echosounder (MBES) bathymetric survey to observe the detailed bottom morphology of the Pantar Strait. We also provide Conductivity Temperature Depth (CTD) data from five stations in the Pantar Strait, which measure the vertical profile of temperature. We identified five basins in the southern Pantar Strait that are likely the sources of the cold-water mass originating in the Mulut Kumbang Strait. The first basin is situated south of the Mulut Kumbang Strait and has a depth of approximately 150 m. The second, third, and fourth basins are aligned further south, with depths of ~350, ~400, and ~600 m, respectively. The deepest and largest basin is located at the southernmost point of the Pantar Strait, adjacent to the Savu Sea, and reaches a maximum depth of 1,060 m. The area of the basin that exceeds 1,000 m in depth covers 4.75 km2. CTD data confirm that temperatures below 10 °C are found at depths greater than 400 m. We infer that the largest and deepest basin at the southern end of the Pantar Strait is a plausible source reservoir for the cold-water mass during the EUE, which is potentially connected to the Mulut Kumbang Strait via a tapered channel.]]>
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