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All Journal ILMU KELAUTAN: Indonesian Journal of Marine Sciences POSITRON Jurnal Kelautan Nasional
Adi Purwandana
Center for Research and Development of Oceanology, Indonesian Institute of Science (P2O-LIPI), Jakarta, Indonesia
Earth & Planetary Sciences Energy Environmental Science Physics

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Characteristics of Internal Solitary Waves near Its Generation Site in the Lombok Strait, Indonesia Purwandana, Adi; Edikusmanto, Edikusmanto; Utari, Putri Adia; Lestiana, Hilda; Saputra, Okta Fajar; Sari, Qurnia Wulan
POSITRON Vol 13, No 2 (2023): Vol. 13 No. 2 Edition
Publisher : Fakultas Matematika dan Ilmu Pengetahuan Alam, Univetsitas Tanjungpura

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.26418/positron.v13i2.61621

Abstract

Evidence of internal solitary waves (ISWs) formation through the Lee wave mechanism in the Lombok Strait was revealed from the echosounder measurements conducted in November 2017. This study is aimed to characterize the property of ISW packet formed around ~30 km away from the generation site, in the southern part of the strait above the Nusa Penida Sill (NPS), by employing Korteweg-de Vries (KdV) solution. The packet can be categorized as the early stage of ISW formation, consisting of two waves of depression, with typical amplitude of 30 m and 10 m, for the first and second wave, respectively. The waves propagated northward with a typical phase speed of ~1.2 m∙s -1. The waves drive a maximum horizontal velocity anomaly of ~0.8 m∙s - 1 and a vertical velocity anomaly of ~10 cm∙s -1. The amplitude of the ISW packet will be potentially amplified during their propagation away from the strait. This study provides an observational based understanding on the early stage of internal tides evolution in the Lombok Strait, particularly highlights the energy transfer of internal tides through the propagation of internal solitary waves.
Vertical and Horizontal Variability of Chlorophyll-a and Its Relationship with Environmental Parameters in the Waters of Sangihe and Talaud Islands, North Sulawesi, Indonesia Firdaus, Mochamad Ramdhan; Rachman, Arief; Fitriya, Nurul; Wijayanti, Lady Ayu Sri; Rozirwan, Rozirwan; Purwandana, Adi; Prayitno, Hanif Budi; Alfiansyah, Yustian Rovi; Sianturi, Oksto Ridho; Sugeha, Hagi Yulia
ILMU KELAUTAN: Indonesian Journal of Marine Sciences Vol 29, No 1 (2024): Ilmu Kelautan
Publisher : Marine Science Department Diponegoro University

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.14710/ik.ijms.29.1.119-132

Abstract

The chlorophyll-a is an important biological parameter that could act as a proxy to indicate the abundance of phytoplankton and the primary productivity of an aquatic ecosystem. This paper investigates the vertical and horizontal variability of chlorophyll-a in the waters of Sangihe and Talaud Islands, Indonesia, and its correlation with water environmental parameters. In this study, the distribution of chlorophyll-a, temperature, salinity, and nutrients (NO3 and PO4) from the surface to a depth of 200 m (photic zone) was measured at 29 research stations. The results showed that the distribution of chlorophyll-a in the waters of the Sangihe-Talaud Islands was varied vertically and horizontally. The waters around the Sangihe Islands generally exhibited a higher chlorophyll-a distribution and shallower Deep Chlorophyll Maxima compared to the water around the Talaud Islands. The concentration of chlorophyll-a varied between 0.0017 and 1.2155 mg.m-3, with most of the water column in Sangihe-Talaud considered oligotrophic, although some stations or depths were mesotrophic or slightly eutrophic. The maximum chlorophyll-a concentration was found in the sub-surface layer at depths between 46 and 101 m. The low N:P ratio (<16) and N:Si ratio (<1) indicate that the water columns of Sangihe-Talaud, up to a depth of 200m, were N-limited. Based on the GAM analysis, chlorophyll-a concentration in Sangihe-Talaud waters was primarily regulated by temperature, salinity, and the N:P ratio, with weak influence from phosphate and the N:Si ratio. The analysis also suggests that primary productivity in Sangihe-Talaud is sensitive to temperature changes, indicating its vulnerability to future warming events.
Distribution and Characteristics of Internal Waves Observed During the Expedition of Jalacitra 2-2022 Banda Putra, I Wayan Sumardana Eka; Atmadipoera, Agus Saleh; Manik, Henry Munandar; Harsono, Gentio; Purwandana, Adi; Hascaryo, Anom Puji
ILMU KELAUTAN: Indonesian Journal of Marine Sciences Vol 29, No 3 (2024): Ilmu Kelautan
Publisher : Marine Science Department Diponegoro University

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.14710/ik.ijms.29.3.359-371

Abstract

Indonesian seas have been known as the hotspot for internal waves (IWs) generation sites. The sinking tragedy of the Indonesian Naval Submarine, KRI Nanggala 402 on 21 April 2021 in the northern Bali Sea was highlights the need of detecting, mapping, and characterizing internal waves in Indonesian waters are compulsory mainly in the Indonesian Archipelago Sea Lanes (IASLs). IASLs is a gateway for sea crossings which can be used by civil navigations, intercontinental trade, and foreign military. This study focused on mapping the distribution and characteristics of internal waves qualitatively using EA 600 Single beam Echosounder (SBES) of the Indonesian Naval Vessel, KRI Rigel 933 during The Jala Citra Expedition 2-2022 Banda. The measurements were conducted around the IASLs route in the Bali Waters, Banda Waters and Buru Waters. The results show that the typical high-frequency non-linear internal waves (HFNWs) with an amplitude of less than 10 m were observed intermittently during the expedition, detected mostly in the narrow passages, rough topography and shallowing waters. Typical characteristics of internal solitary waves (ISWs) were also observed with typical amplitudes of ~20 – 65 m. An ISWs extreme events found in this study verified the "turbulent water" that was reported in in the IASLs around the Underwater Seamount (US) Nieuwerkerk waters, in 1925 during the Snellius Expedition. The detection of internal wave events using acoustic equipment, the single beam echosounder is considered effective which can later be used as the guidance for marine activities in the water column.
Karakteristik Proses Pendangkalan Gelombang Soliter Internal di Sisi Utara Perairan Laut Flores Putra, I Wayan Sumardana Eka; Atmadipoera, Agus Saleh; Manik, Henry Munandar; Harsono, Gentio; Purwandana, Adi
Jurnal Kelautan Nasional Vol 19, No 2 (2024): Agustus
Publisher : Pusat Riset Kelautan

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.15578/jkn.v19i2.14049

Abstract

Kemunculan Gelombang Soliter Internal (GSI) di Laut Flores sering kali tertangkap oleh citra satelit dengan pusat pembangkitan yang berasal dari Selat Ombai. Namun, belum ada penelitian yang mengungkap secara detail nasib fenomena tersebut sesaat setelah dibangkitan. Karakteristik GSI tersebut diselidiki berdasarkan kemunculannya pada Synthetic Aperture Radar (SAR) dan citra kolom air (Water Coloum Imaging-WCI) peralatan akustik hidrografi (multibeams echosounders-MBES) saat kegiatan Ekspedisi Jala Citra (EJC) 3-2023 di Perairan Flores pada tanggal 25 April 2023. Tujuan dari penelitian ini adalah menganalisa dan mengungkapkan nasib perambatan GSI dari Selat Ombai hingga mengalami pendangkalan dan pemecahan di perairan Teluk Bone, Sulawesi. Metode dalam penelitian ini adalah menggunakan data hasil perekaman citra satelit dan peralatan akustik hidrografi (MBES). Hasil penelitian mengungkapkan bahwa Perairan Teluk Bone dikarekteristikan sebagai lokasi propagasi, pendangkalan dan pemecahan yang berasal dari pembangkitan GSI di Selat Ombai. Nilai amplitudo GSI yang mengalamai pendangkalan di Teluk Bone dikarakterisasi berubah menjadi 4-10 kali lebih kecil dari pusat pembangkitan GSI (Selat Ombai) akibat perubahan kedalaman dan memecah akibat menabrak dinding tebing/lereng topografi dasar laut dan diduga berubah menjadi boluses. Karakteritik massa air saat kenampakan GSI di Laut Flores tanggal 25 April 2023 di dominasi oleh massa air Samudera Pasifik yang terbawa oleh Arlindo dari Selat Makassar. Kemunculan GSI juga merubah struktur kolom air yaitu suhu, salinitas dan densitas yang merupakan faktor penting dalam propagasi akustik serta berimplikasi terhadap proses kegiatan maritim di Perairan Indonesia.
Co-Authors Agus Atmadipoera Alfiansyah, Yustian Rovi Arief Rachman Edikusmanto, Edikusmanto Firdaus, Mochamad Ramdhan Gentio Harsono Hanif Budi Prayitno Hascaryo, Anom Puji Henry M. Manik Hilda Lestiana Nurul Fitriya Oksto Ridho Sianturi Putra, I Wayan Sumardana Eka Rozirwan . Saputra, Okta Fajar Sari, Qurnia Wulan Sugeha, Hagi Yulia Utari, Putri Adia Wijayanti, Lady Ayu Sri