ANALISIS MASA AIR DAN ESTIMASI TRANSPORT ARUS BAWAH EKUATOR PADA BUJUR 90°E SELAMA INDONESIA PRIMA 2017

Edi Kusmanto, Siswanto Siswanto

Abstract


Arus bawah permukaan khatulistiwa (Equatorial Undercurrent, EUC) memainkan peran penting dalam dinamika Samudra Hindia bagian timur. EUC menyuplai massa air dengan salinitas tinggi yang masuk ke perairan Indonesia. Artikel ini mengkaji EUC dan analisis massa airnya di Samudera Hindia bagian timur pada bujur 90°E dari lintasan 2°S – 2°N pada tanggal 1 – 3 Maret 2017 yang merupakan bagian dari ekspedisi “Indonesia Initiative on maritime Observation and Analysis” (Indonesia Prima 2017). Hasil analisis data suhu, salinitas, dan sigma – t yang diperoleh dari instrumen conductivity, temperature and depth (CTD) pada lima stasiun (CTD11–CTD14) dan profil arus dari Shipboard Acoustic Doppler Current Profiles (SADCP) menunjukkan adanya asupan massa air bersalinitas tinggi dari Laut Arab (Arabian Sea High Salinity Water, ASHSW) yang dicirikan oleh salinitas maksimum (35.15 - 35.2 PSU) pada rentang suhu 18°C - 23°C dan densitas 23 – 25 kg/m3. ASHSW dibawa oleh EUC dari Samudera Hindia bagian barat pada lapisan termoklin atas. Ditemukan bahwa EUC selama penelitian ini memiliki kecenderungan karakteristik berupa asimetris lebih kuat ke arah utara khatulistiwa. EUC mengalir ke timur dengan kecepatan maksimum 94 cm/sec. Estimasi transport massa air pada poros EUC berdasarkan kontur salinitas 35.15 dan 35.2 PSU masing masing sebesar  ̴ 3.4 Sv dan  ̴ 1.4 Sv, sedangkan pada salinitas 35.00 – 35.10 PSU sebesar  ̴ 8.7 Sv. Estimasi total transport massa air EUC pada penelitian ini sebesar  ̴ 13.5 Sv.

 

Equatorial Undercurrent (EUC) plays an important role in the dynamic of the eastern Indian Ocean. EUC supplies water masses with high salinity into Indonesian waters. This article examines the EUC and its water mass characteristics at 90°E across 2°S - 2°N on 1st - 3rd March 2017 which is part of the Initiative on Maritime Observation and Analysis Expedition (Indonesian Prima 2017). The analysis of temperature, salinity, and sigma-t data obtained from conductivity, temperature and depth (CTD) instruments at five stations (CTD11-CTD14) and current profiles of Shipboard Acoustic Doppler Current Profiles (SADCP) indicate the presence of high speed water column flowing the Arabian Sea High Salinity Water (ASHSW) as characterized by maximum salinity (35.15 - 35.2 PSU) in the temperature range of 18 ° C - 23 ° C and density of 23 - 25 kg / m3. ASHSW is carried by EUC from the western Indian Ocean at the upper thermocline layer. It was found that EUC during this study had a tendency to be asymmetrically stronger to the north of the equator. The analysis shows a maximum speed of 94 cm/sec and a transport estimated of EUC water masses based on salinity contour 35.15 and 35.2 PSU respectively of ̴ 3.4 Sv and ̴ 1.4 Sv, while at salinity 35.00 - 35.10 PSU of ̴ 8.7 Sv. The total estimated EUC mass transport calculated in this study is ̴ 13.5 Sv.

Keywords


Indonesia PRIMA; Arus bawah permukaan khatulistiwa; Samudera Hindia; massa air laut; aliran; Equatorial Undercurrent; Indian Ocean; water mass; transport

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DOI: http://dx.doi.org/10.31172/jmg.v19i2.522

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