Current Structure and Spatial Variation of Indonesian Throughflow in Makassar Strait Under Ewin 2013 (Struktur Arus dan Variasi Spasial Arlindo di Selat Makassar dari Ewin 2013)

Abstract

Selat Makassar (SM) merupakan pintu masuk utama Arus Lintas Indonesia (Arlindo) membawa transport Arlindo sekitar 75% dari total 15 Sv. Pengukuran mooring arus di Kanal Labani telah dilakukan sejak tahun 1996, namun pengukuran hidrografi yang mencakup seluruh kawasan SM jarang dilakukan. Kontur selat yang berupa kanal dengan keragaman batimetri sangat mempengaruhi karakteristik massa air yang bergerak di dalamnya sehingga diperlukan penelitian mencakup seluruh kawasan SM. Tujuan penelitian ini adalah mengkaji variasi spasial dan struktur arus dan massa air Arlindo di kawasan SM dari hasil ekspedisi EWIN Juni 2013. Data hidrografi yang digunakan terdiri dari 29 casts CTD yang tersebar di kawasan SM dan data arus di kedalaman 0-125 m dari shipboard ADCP sepanjang lintasan survei. Hasil penelitian menunjukkan Arlindo Makassar dicirikan arus jet kuat intensif di kedalaman termoklin (75-125 m), dimana pola alirannya mengarah ke selatan sampai barat daya di pintu masuk utara SM. Arus ini berlanjut sampai mendekati lintang 2°LS, yang selanjutnya arah alirannya berubah ke tenggara menyusuri lereng dangkalan Kalimantan yang mengarah ke Kanal Labani. Arus jet berubah ke arah selatan sampai tenggara di kanal ini dan menjadi lebih kuat. Sirkulasi di sisi tepi barat laut SM terbentuk pusaran arus searah jarum jam. Stratifikasi massa air Arlindo Makassar didominasi massa air Pasifik Utara, yaitu North Pacific Subtropical Water (NPSW) di kedalaman termoklin dan North Pacific Intermediate Water (NPIW) di bawah termoklin. Terdapat variasi spasial massa air NPSW dan NPIW, dimana semakin kearah selatan nilai salinitas maksimum (minimum) NPSW (NPIW) semakin berkurang sekitar 0.03 psu. Ketebalan lapisan termoklin sisi timur selat lebih besar sehingga distribusi vertikal massa air Pasifik Utara tersebut cenderung lebih kuat di sisi timur sehingga ditemukan intensifikasi Arlindo ke arah barat Selat Makassar.

Seasonal variation of mixed layer depth and thermocline thickness from the ctd argo float data in the Southern Makassar Strait

“…The mixed layer in the west season has the thickest layer compared to other seasons, where in this season the depth of the mixed layer is at 0-93 m. The southeast monsoon has the thinnest mixed layer thickness compared to other season which is at a depth of 0-46 m. The thickness of the mixed layer in the first transitional season and second transitional seasons is normal compared to the west and southeast monsoon, which are at a depth of 0-84 m. The condition of the thermocline layer in the west season has a thinner thickness, which is at a depth of 82-216 m. The southeast monsoon has the thickest thermocline layer compared to other seasons, at a depth of 42-234 m. The first and second transitional seasons have a normal thermocline layer thickness at a depth of 58-210-m. This is in accordance with research conducted by [15] which states that in the southeast monsoon the Makassar Strait has the thickest thermocline layer and the mixed layer in the southeast monsoon has a thin layer thickness and in the northwest monsoon occurs in contrast to the southeast monsoon. The factor causing the thickening of the thermocline layer is thought to be related to the strengthening of ITF and modulated by the southeast monsoon with Ekman transport towards to the south [16].…”

“…Currents in both seasons branch towards the Java Sea and the Flores Sea and the direction of the current strength is greater pushing the water mass towards the Java Sea than towards the Flores Sea. This is in accordance with research conducted by Horhoruw [15] where the current branching occurs before passing through the Dewakang Sill and the direction of the greater current strength pushes the water mass towards the west side compare to the east side.…”

Simulated circulation and trajectory analysis in the Makassar Strait

“…The temperature in Makassar Strait shows vertical variations, the water temperature decreases with depth with a range from 30°C -5°C at depthS of 0-700 m. Temporal variations of SST in Makassar Strait also fluctuated with higher temperatures during the NWM. This fluctuation is due to the variability inputs of water masses from the South China Sea and the Java Sea [23,24]. During the SEM, the SST in Makassar Strait tends to be lower, raising the colder water layer and thinning of the mixed layer.…”

Keragaman Genetik Penyu Lekang (Lepidochelys olivacea) Dan Kaitannya Dengan Pola Arus Di Perairan Samudera Hindia Dan Perairan Tengah Indonesia

“…Data yang digunakan pa a penelitian ini meliputi data time s eries rata -rata harian untuk komponen arus zonal, arus meridional, suhu, dan salinitas dekat permukaan (permukaan hingga 6 m) pada tahun 2015. Pola arus dianalisis menggunakan software Ferret yang dioperasikan melalui Sistem operasi LINUX dalam pemrosesannya (Horhoruw, 2016). Pola sirkulasi ini diharapkan dapat memberikan informasi tambahan tentang kemungkinan penyebaran penyu remaja atau penyu dewasa yang bermigrasi di ketiga wilayah tersebut, dan dapat membantu menjelaskan hubungan kekerabatan biogeografinya (Permadi et al, 2015).…”