Observed Transport Variations in the Maluku Channel of the Indonesian Seas Associated with Western Boundary Current Changes

Abstract

The Maluku Channel is a major opening of the eastern Indonesian Seas to the western Pacific Ocean, the upper-ocean currents of which have rarely been observed historically. During December 2012–November 2016, long time series of the upper Maluku Channel transport are measured successfully for the first time using subsurface oceanic moorings. The measurements show significant intraseasonal-to-interannual variability of over 14 Sv (1 Sv ≡ 106 m3 s−1) in the upper 300 m or so, with a mean transport of 1.04–1.31 Sv northward and a significant southward interannual change of over 3.5 Sv in the spring of 2014. Coincident with the interannual transport change is the Mindanao Current, choked at the entrance of the Indonesian Seas, which is significantly different from its climatological retroflection in fall–winter. A high-resolution numerical simulation suggests that the variations of the Maluku Channel currents are associated with the shifting of the Mindanao Current retroflection. It is suggested that the shifting of the Mindanao Current outside the Sulawesi Sea in the spring of 2014 elevates the sea level at the entrance of the Indonesian Seas, which drives the anomalous transport through the Maluku Channel. The results suggest the importance of the western boundary current nonlinearity in driving the transport variability of the Indonesian Throughflow.

Interannual Variability of the Sulawesi Sea Circulation Forced by Indo‐Pacific Planetary Waves

“…Ship‐board ADCP observations by Kashino et al () were obtained in the northern Maluku Sea, but the single transect of velocity data was inevitably aliased by tides and internal waves that are strong in the area. Here we take advantage of the recent moored ADCP observations in the Maluku Channel (Yuan, Li, et al, ) to assess the model's skills in reproducing the zonal and meridional currents from the mooring observations at 2°N, 126.48°E (Figure ). The model currents are averaged in a 1/6° × 1/6° box surrounding the mooring location.…”

“…The correlation between the SLA at the Philippine coast and at the Maluku Channel (e.g., Figure ) suggests that the SLA variability could also be impacted by direct advection via the Mindanao Current. In addition, nonlinear dynamics associated with movement of the Mindanao Current retroflection may also drive SLA variability in the Maluku Channel (Yuan, Li, et al, ).…”

“…Recent studies find that the western boundary reflections are nonlinear (Yuan, ; Yuan et al, ). The nonlinear reflection is associated with the shifting of the Mindanao Current path (Yuan, Li, et al, ). In the off‐equatorial Pacific Ocean, Rossby waves propagate westward and impinge on the coast of Mindanao, and some of that Rossby wave energy can reflect as eastward propagating equatorial coupled waves (White et al, ).…”

Dinamika Massa Air di Sekitar Pulau-Pulau Kecil Terluar (PPKT) Perairan Utara Papua

“…Pola arus yang sedikit berbeda terlihat pada kedalaman 100 -150 m. Di perairan utara Papua, arus laut dominan bergerak ke arah barat laut hingga barat daya memasuki perairan Indonesia dengan kecepatan 40 hingga 80 m/s. Arus ini diduga merupakan sumber masuknya massa air Samudera Pasifik ke perairan Indonesia melalui sistem ITF (Gordon & Fine, 1996;Gordon et al, 2010;Sprintall et al, 2014;Yuan et al, 2018). Di Laut Halmahera, arus memasuki perairan Indonesia melalui sisi barat dan keluar melalui sisi timur.…”

“…Kondisi yang berbeda terlihat pula di Laut Maluku yang menunjukkan dominasi arus yang bergerak ke arah utara. Kondisi ini sesuai dengan hasil pengukuran arus laut menggunakan sistem mooring yang menunjukkan bahwa pada bulan Oktober hingga Februari, arus laut di Laut Maluku cenderung bergerak ke utara hingga timur laut (Yuan et al, 2018).…”