Turbulent mixing limits mussel feeding: direct estimates of feeding rate and vertical diffusivity

Abstract The Indonesian Throughflow (ITF) via its western path conveys mainly North Pacific water origin with Smax thermocline water and Smin intermediate water from its entry portal in Sangihe-Talaud arcs to the main outflow straits in Lombok, Ombai and Timor passage. Along its route, the throughflow water characteristics transforms significantly due to strong diapycnal mixing forced by internal tidal waves interaction along complex topography such as passages, sill, straits, and shallow islands chains. This paper reports a brief estimate of turbulent mixing profiles in Sangihe chains, and Makassar Strait. The CTD dataset are obtained from the year of maritime continent (YMC) Cruise in August 2019 on board the R.V. Baruna Jaya I. The Thorpe method is used to analysis dissipation energy ( ε ) and vertical diffusivity (Kz ) from CTD dataset. It is shown that the highest ε epsilon 5.87 × 10−7 Wkg −1 and Kz 4.42 × 10−3 m2s 1 are found in the Sangihe area. In Labani Channel and Dewakang Sill the averaged vertical diffusivity is much weaker at the order of 10−4 m 2s1. Thus, Sangihe Chains station have the highest values compared to other stations at depth 950-1000 meters.

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Percampuran Turbulen Di Laut Sulawesi Menggunakan Estimasi Thorpe Analisis

Jurnal Kelautan Tropis ◽

10.14710/jkt.v24i2.7352 ◽

2021 ◽

Vol 24 (2) ◽

pp. 211-222

Author(s):

Hadi Hermansyah ◽

Agus Saleh Atmadipoera ◽

Tri Prartono ◽

Indra Jaya ◽

Fadli Syamsudin

Keyword(s):

Turbulent Mixing ◽

Large Scale ◽

Near Field ◽

Tidal Energy ◽

Eddy Diffusivity ◽

Internal Tides ◽

Strong Mixing ◽

Ocean Energy ◽

Average Value ◽

Vertical Diffusivity

Dissipation of internal tides will cause mixing, The mixing process at sea plays a key role in controlling large-scale circulation and ocean energy distribution. The purpose of this research was to estimate the turbulent mixing values (vertical eddy diffusivity) of water mass using Thorpe analysis. The results showed that the location where strong mixing occurred in the “near-field” area around Sangihe Island with vertical diffusivity value . Even in areas far-field(far from the generating site) are found vertical diffusivity , the result of internal propagation tides dissipation. Based on the result of the observation, it shows that the level of kinetic energy of eddy turbulen dissipation (ε) in the Sulawesi Sea on all layers has an average value of . The value of ε in the thermocline layer is greatest compared to the mixed surface layer and the almost homogeneous deep layer, the increase in mixing in the area near the ridge due to the closer water column to the base topography. The average turbulent rate of , the strongest fluctuation of value occurs in the thermocline layer, ranging from to with an average of about . The value of this turbulent mixing is higher than the previous measurements in some Indonesian ocean. This is allegedly due to the existence of a strong internal tidal energy and its interaction with topography in the Sulawesi Sea.Disipasi dari pasang surut internal akan menyebabkan terjadinya percampuran, proses percampuran di laut memainkan peran kunci dalam mengendalikan sirkulasi skala besar dan distribusi energi lautan. Tujuan dari penelitian ini adalah untuk mengestimasi nilai percampuran turbulen (difusivitas eddy vertikal) massa air dengan analisis Thorpe. Hasil penelitian ini menunjukkan bahwa percampuran yang kuat terjadi di area sekitar Pulau Sangihe-Talaud dengan nilai difusivitas vertikal . Bahkan pada area yang jauh dari pusat pembangkitan ditemukan difusivitas vertikal , hasil disipasi propagasi pasang surut internal. Berdasarkan hasil pengamatan menunjukan bahwa rata-rata tingkat energi kinetik disipasi turbulen eddy Laut Sulawesi pada semua lapisan adalah . Nilai di lapisan termoklin paling besar dibandingkan dengan lapisan permukaan tercampur dan lapisan dalam yang hampir homogen, peningkatan percampuran di daerah dekat ridge disebabkan makin mendekatnya kolom air dengan topografi dasar. Rata-rata nilai percampuran turbulen sebesar , fluktuasi nilai yang paling kuat terjadi di lapisan termoklin, yang berkisar yaitu antara sampai dengan rerata sekitar . Nilai percampuran turbulen ini lebih tinggi dibandingkan dengan pengukuran sebelumnya di beberapa perairan Indonesia. Hal ini diduga karena adanya energi pasang surut internal yang kuat serta interaksinya dengan topografi yang ada di Laut Sulawesi.

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Turbulent Mixing in Raja Ampat Sea

Applied Mechanics and Materials ◽

10.4028/www.scientific.net/amm.862.9 ◽

2017 ◽

Vol 862 ◽

pp. 9-15 ◽

Cited By ~ 1

Author(s):

Aditya Pamungkas ◽

Ivonne M. Radjawane ◽

Hadikusumah

Keyword(s):

Kinetic Energy ◽

Turbulent Kinetic Energy ◽

Turbulent Mixing ◽

Richardson Number ◽

Complex Geometry ◽

Energy Dissipation Rate ◽

Diffusivity Coefficient ◽

Indonesian Throughflow ◽

Average Value ◽

Vertical Diffusivity

Raja Ampat Sea has a complex geometry and passed by Indonesian Throughflow (ITF) causing a very dynamic water condition, that condition also amplified by turbulent mixing. To gain better understanding of process and extent of turbulent mixing in Raja Ampat Sea, this research calculate Brunt-Vaisala frequency, Richardson number, turbulent kinetic energy dissipation rate and vertical diffusivity coefficient. The data obtained from Expedition Widya Nusantara (EWIN) by P2O-LIPI in the territorial of Raja Ampat Sea on 14-24 November 2007, by using 12 out of 33 observation stations. From this research, it is known that in 0-40 m (mixed layer) and 250-400 m (deep layer) have Richardson number (Ri) less than 0.25 and high vertical diffusivity coefficient (Kv), It proves a strong turbulent mixing occurs at those depth. Furthermore, Raja Ampat Sea has strong turbulent mixing with average value of turbulent kinetic energy is 2.64 WKg-1and vertical diffusivity coefficient is 1.65x10-3 m2s.

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