North Pacific Water Mass Contribution in the Northern Sea of Lembata Island, East Nusa Tenggara

Abstract

As the Indonesian Throughflow (ITF) passes through the Flores Sea, we expect it will affect the water mass character in the northern sea of Lembata Island. Therefore, we examined the contribution of North Pacific (NP) water mass, i.e., the North Pacific Subtropical Water (NPSW) and the North Pacific Intermediate Water (NPIW) in the study area. We used 30 CTD casts from OTEC Geological Survey Center Expedition 2017 and ARGO float data, analyzed through the TS diagram and Optimum Multiparameter (OMP). The remnant of the NPSW (NPIW) core layer was found at 140-190 (220-330) m depth, deeper than it occurs in the NP source regime, and of previous pathway seas i.e. Makassar Strait. The OMP results show NPSW (NPIW) contribution is about 20-75 (50-70)%. Contrary to the ITF direction from the western pathway, the value of NP water mass contribution is larger in the eastern than in the western part of the northern sea of Lembata Island. We speculated the ITF flows away from the northern sea of Lembata Island, blocked by the headland in the eastern part of Flores Island. Then a small part of ITF is deflected back to the west, but unfortunately, no detailed current is available in the study area.