Indonesian Throughflow (ITF) variability in Halmahera Sea and its coherency with New Guinea Coastal Current

Abstract

The Indonesian Throughflow passing through the Halmahera Sea (H-ITF) is supposed to be supplied by the western boundary current system, particularly from the New Guinea Coastal Current (NGCC). However, characteristics of H-ITF and NGCC is not well understood yet. This paper aims to investigate vertical structure, transport volume estimate, and transport variability of H-ITF and its coherency with NGCC in the upper 200 m depth. The dataset are obtained from daily INDESO model output (2008-2014). H-ITF across latitude of 0.3°S is indicated by a strong intensified southward flow in upper 150 m with 67.2 km width, and mean transport volume 2.35 (±1.94) Sv (southward). Furthermore, NGCC across 134°E is characterized with 291.2 km width, strong velocity core (>0.4 m/s) in the upper 200 m depth, and transport volume 13.47 (±6.6) Sv (westward). The model indicated that H-ITF is supplied by 17.45% of NGCC. Variability of H-ITF is dominated by intraseasonal period. High coherence (0.85) between H-ITF and NGCC transport is revealed on intraseasonal (45-day) period, with NGCC signal is 4.86 days leading to H-ITF. This sinyal may be associated with a passage of westward equatorial Pacific waves into Halmahera Sea.