Distribusi Percampuran Turbulen di Perairan Selat Alor  (Distribution of Turbulence Mixing in Alor Strait)

Selat Alor merupakan kanal terdalam setelah Selat Ombai di kepulauan Alor. Kontribusinya sebagai salah satu celah keluar Arus Lintas Indonesia (Arlindo) belum banyak dikaji hingga saat ini. Selat Alor memisahkan Laut Flores dan Laut Sawu, dan memiliki sill yang tinggi di dalamnya, diduga turbulensi akibat interaksi antara aliran selat dengan topografi dasar dapat memicu percampuran dan memodifikasi properti massa air yang melaluinya. Tujuan dari penelitian ini adalah untuk mengkuantifikasi transformasi massa air yang melalui Selat Alor dan mengkaji kemungkinan percampuran di dalam selat berdasarkan estimasi sesaat properti percampuran, yakni percampuran turbulen menggunakan metode skala Thorpe. Penurunan CTD dilakukan di 15 stasiun di perairan Selat Alor. Diperoleh hasil bahwa kontur kedalaman yang menghubungkan Laut Flores dengan Laut Sawu adalah ~300 m pada kanal utama. Salinitas maksimum massa air Subtropis Pasifik Utara (NPSW) dar i Laut Flores di Selat Alor banyak mengalami reduksi akibat intensifnya percampuran yang diduga dipicu oleh topografi dasar dan aliran selat yang menghasilkan turbulensi. Lapisan salinitas maksimum Massa Air Subtropis Samudera Hindia Utara (NISW) pada σθ = 23,5-24,5 terdeteksi di bagian selatan selat (Laut sawu). Jejak massa air NISW menurun dan banyak tereduksi mendekati pintu selatan selat. Intrusi Massa Air Lapisan Menengah Samudera Hindia Utara (NIIW) juga dijumpai di lapisan bawah Laut Sawu, konsisten dengan profil arus pada lapisan bawah. Rata-rata nilai difusivitas vertikal eddy (Kρ) di Selat Alor bagian utara memiliki orde of 10-3 m2 s-1, dan di bagian selatan memiliki orde bervariasi, 10-6-10-4 m2 s-1. Penyempitan celah Selat Alor diduga merupakan pemicu turbulensi tinggi aliran yang berkontribusi pada tingginya nilai difusivitas vertikal. Kata kunci: Arlindo, percampuran turbulen, difusivitas vertikal, Selat Alor Alor Strait is the deepest channel in Alor islands after Ombai Strait. Contribution of the strait as one of the secondary exit passages of Indonesian Throughflow (ITF) has not been studied yet. The strait separates Flores Sea and Sawu Sea, and is featured by the existence of high sill within the strait, suggested that turbulence due to interaction between strait flow and bottom topography could drive mixing and then modify the water mass properties. The purpose of this study is to investigate transformation of ITF water mass and turbulent mixing process with Thorpe scale method. A hydrographic survey has been carried out in July 2011, in which 15 CTD casts were lowered in the strait. The results show that Alor sill depth is about 300 ms in the main gate. Maximum salinity of NPSW from Flores Sea within Alor Strait is significantly reduced due to strong mixing, perhaps driven by bottom topography and strait flow which creates turbulence. NISW (Northern Indian Subtropical Water) with maximum salinity layer at σθ = 23,5-24,5 is dominant in the southern part of Alor Strait (i.e. Sawu Sea). The existence of NIIW (North Indian Intermediate Water) is also found in the deeper layer of Sawu Sea. The average value of vertical eddy diffussivity (Kρ) estimate in the thermocline layer and deep layer in northern part and central part of strait channel is within the order of 10-3 m2 s-1. Lower order of Kρ in the thermocline layer and deep layer were found in southern part of the Strait (Sawu Sea), ranging from 10-6 to 10-4 m2 s-1. These indicate that the existence of sills in the northern part and central part of Alor Strait could drive mixing significantly. Narrowing passage of Alor Strait probably contribute to the high value of vertical eddy diffusivity due to highly turbulence flow. Keywords: Indonesian Throughflow (ITF), turbulent mixing, vertical diffussivity, Alor Strait

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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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Transformation and mixing of North Pacific Water Mass in Sangihe-Talaud in August 2019

IOP Conference Series Earth and Environmental Science ◽

10.1088/1755-1315/944/1/012053 ◽

2021 ◽

Vol 944 (1) ◽

pp. 012053

Author(s):

I Y Sani ◽

A S Atmadipoera ◽

A Purwandana ◽

F Syamsudin

Keyword(s):

Turbulent Mixing ◽

North Pacific ◽

Water Mass ◽

Bottom Topography ◽

Mass Composition ◽

Intermediate Water ◽

Interior Layer ◽

Maritime Continent ◽

Pacific Water ◽

O 10

Abstract Along the pathway, ITF water is considered to be transformed due to strong diapycnal mixing. This study aims to describe the structure of ITF water and to estimate turbulent mixing. The number of 6 CTD casts and 9 repeated CTD “yoyo” measurements were obtained from the “Years of Maritime Continent” YMC cruise (a joint cruise between BPPT/IPB/UNUD-Univ. Tokyo/JAMSTEC) and onboard R.V. Baruna Jaya IV in August 2019. The CTD datasets are processed with SBE Data Processing and analyzed for water mass composition, as well as turbulent mixing with Thorpe method. The results showed that thermocline water of NPSW with S-max, and intermediate water of NPIW with S-min from North Pacific origin are dominant. Transformation of NPSW and NPIW along their pathway can be identified from decreasing S-max of NPSW and increasing S-min of NPIW. Estimates of ϵ and Kρ are O(10−5) m2s−2 and 10−2 m2 s−1, respectively. High mixing occur also in the interior layer with the e and the Kp O(10−6) m2s−2 and O(10−1) m2 s−1, respectively. This is related to barotropic tidal activity that interacts with the bottom topography where there are many sills, causing the formation of strong baroclinic tides.

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TURBULENT MIXING IN OMBAI STRAIT

Jurnal Ilmu dan Teknologi Kelautan Tropis ◽

10.29244/jitkt.v7i1.9778 ◽

2015 ◽

Vol 7 (1) ◽

Cited By ~ 3

Author(s):

Yulianto Suteja ◽

Mulia Purba ◽

Agus S. Atmadipoera

Keyword(s):

Turbulent Mixing ◽

Water Mass ◽

Internal Tide ◽

Tidal Energy ◽

Homogeneous Layer ◽

Indonesian Throughflow ◽

Mixing Processes ◽

Average Value ◽

Cycle 24 ◽

The One

Ombai Strait is one of the exit passages of Indonesian Throughflow (ITF) which conveys hotspot of strong internal tidal energy. Internal tide is the one of main energy which causes mixing processes in the oceans and could lead to changes in water mass characteristics. The purpose of this research was to estimate the turbulent mixing by using Thorpe analysis. Nine CTD cast were obtained for one tidal cycle (24 hours) in Ombai Strait. The results showed the average value of the turbulent mixing is 833.5 x 10-4 m2s-1, the highest found in deep homogeneous layer (2383.4x 10-4 m2s-1), followed by mixed surface layer (103.0 x 10-4 m2s-1) and thermocline (14.2 x 10-4 m2s-1). This Turbulent mixing value is much higher than the previous measurement in Indonesian Sea. This is presumably due to the strong internal tidal energy and its interaction with existing deep sill in Ombai Strait. Keywords: Indonesian throughflow (ITF), Ombai Strait, turbulent mixing

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TURBULENT MIXING IN OMBAI STRAIT

Jurnal Ilmu dan Teknologi Kelautan Tropis ◽

10.28930/jitkt.v7i1.9778 ◽

2015 ◽

Vol 7 (1) ◽

Author(s):

Yulianto Suteja ◽

Mulia Purba ◽

Agus S. Atmadipoera

Keyword(s):

Turbulent Mixing ◽

Water Mass ◽

Tidal Energy ◽

Previous Measurement ◽

Homogeneous Layer ◽

Indonesian Throughflow ◽

Mixing Processes ◽

Average Value ◽

Cycle 24 ◽

The One

Ombai Strait is one of the exit passages of Indonesian Throughflow (ITF) which conveys hotspot of strong internal tidal energy. Internal tide is the one of main energy which causes mixing processes in the oceans and could lead to changes in water mass characteristics. The purpose of this research was to estimate the turbulent mixing by using Thorpe analysis. Nine CTD cast were obtained for one tidal cycle (24 hours) in Ombai Strait. The results showed the average value of the turbulent mixing is 833.5 x 10-4 m2s-1, the highest found in deep homogeneous layer (2383.4x 10-4 m2s-1), followed by mixed surface layer (103.0 x 10-4 m2s-1) and thermocline (14.2 x 10-4 m2s-1). This Turbulent mixing value is much higher than the previous measurement in Indonesian Sea. This is presumably due to the strong internal tidal energy and its interaction with existing deep sill in Ombai Strait. Keywords: Indonesian throughflow (ITF), Ombai Strait, turbulent mixing

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Spatial distribution of turbulent diapycnal mixing along the Mindanao current inferred from rapid-sampling Argo floats

Journal of Oceanography ◽

10.1007/s10872-021-00624-3 ◽

2022 ◽

Author(s):

Ying He ◽

Jianing Wang ◽

Fan Wang ◽

Toshiyuki Hibiya

Keyword(s):

Turbulent Mixing ◽

North Pacific ◽

Water Mass ◽

Strong Mixing ◽

Western Boundary ◽

Diapycnal Mixing ◽

The North ◽

Rapid Sampling ◽

Mindanao Current ◽

The North Pacific

AbstractThe Mindanao Current (MC) bridges the North Pacific low-latitude western boundary current system region and the Indonesian Seas by supplying the North Pacific waters to the Indonesian Throughflow. Although the previous study speculated that the diapycnal mixing along the MC might be strong on the basis of the water mass analysis of the gridded climatologic dataset, the real spatial distribution of diapycnal mixing along the MC has remained to be clarified. We tackle this question here by applying a finescale parameterization to temperature and salinity profiles obtained using two rapid-sampling profiling Argo floats that drifted along the MC. The western boundary (WB) region close to the Mindanao Islands and the Sangihe Strait are the two mixing hotspots along the MC, with energy dissipation rate ε and diapycnal diffusivity Kρ enhanced up to ~ 10–6 W kg−1 and ~ 10–3 m2 s−1, respectively. Except for the above two mixing hotspots, the turbulent mixing along the MC is mostly weak, with ε and Kρ to be 10–11–10–9 W kg−1 and 10–6–10–5 m2 s−1, respectively. Strong mixing in the Sangihe Strait can be basically attributed to the existence of internal tides, whereas strong mixing in the WB region suggests the existence of internal lee waves. We also find that water mass transformation along the MC mainly occurs in the Sangihe Strait where the water masses are subjected to strong turbulent mixing during a long residence time.

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Thermohaline properties in the Eastern Mediterranean in the last three decades: is the basin returning to the pre-EMT situation?

Ocean Science Discussions ◽

10.5194/osd-11-391-2014 ◽

2014 ◽

Vol 11 (1) ◽

pp. 391-423 ◽

Cited By ~ 4

Author(s):

V. Cardin ◽

G. Civitarese ◽

D. Hainbucher ◽

M. Bensi ◽

A. Rubino

Keyword(s):

Deep Water ◽

Water Mass ◽

Deep Layer ◽

Eastern Mediterranean ◽

Salt Content ◽

Intermediate Water ◽

Levantine Basin ◽

Mass Properties ◽

Wide Scale ◽

East West

Abstract. We present temperature, salinity and oxygen data collected during the M84/3 and P414 cruises in April and June 2011 on a basin-wide scale to determine the ongoing oceanographic characteristics in the Eastern Mediterranean (EM). The east–west transect through the EM sampled during the M84/3 cruise together with data gained on previous cruises over the period 1987–2011 are analysed in terms of regional aspects of the evolution of water mass properties and heat and salt content variation. The present state of the EM basin is also evaluated in the context of the evolution of the Eastern Mediterranean Transient (EMT). From this analysis we can infer that the state of the basin is still far from achieving the pre-EMT conditions. Indeed, the 2011 oceanographic conditions of the deep layer of the central Ionian lie between the thermohaline characteristics of the EMT and the pre-EMT phase, indicating a possible slow return towards the latter. In addition, the thermohaline properties of the Adriatic Deep Water are still in line (warmer and saltier) as when it restarted to produce dense waters after the EMT. Special attention is given to the variability of thermohaline properties of the Levantine Intermediate Water and Adriatic Deep Water in three main areas: the Cretan, the central Levantine and the central Ionian Seas. Finally, this study evidences the relationships among the hydrological property distributions of the upper-layer in the Levantine basin and the circulation regime in the Ionian.

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Indirect estimation of turbulent mixing in western route of Indonesian throughflow

IOP Conference Series Earth and Environmental Science ◽

10.1088/1755-1315/944/1/012059 ◽

2021 ◽

Vol 944 (1) ◽

pp. 012059

Author(s):

M Firdaus ◽

H Rahmawitri ◽

S Haryoadji ◽

A S Atmadipoera ◽

Y Suteja ◽

...

Keyword(s):

Turbulent Mixing ◽

Intermediate Water ◽

Indonesian Throughflow ◽

Pacific Water ◽

Dissipation Energy ◽

Tidal Waves ◽

Water Characteristics ◽

Vertical Diffusivity ◽

Water Origin ◽

Waves Interaction

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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Observational estimates of turbulent mixing in the southeast Indian Ocean

Journal of Physical Oceanography ◽

10.1175/jpo-d-20-0036.1 ◽

2021 ◽

Author(s):

Ajitha Cyriac ◽

Helen E. Phillips ◽

Nathaniel L. Bindoff ◽

Huabin Mao ◽

Ming Feng

Keyword(s):

Indian Ocean ◽

Turbulent Mixing ◽

Large Scale ◽

Bottom Topography ◽

Intermediate Water ◽

Depth Range ◽

Mean Flow ◽

Mode Water ◽

South Indian ◽

Spatio Temporal

AbstractThis study investigates the spatio-temporal variability of turbulent mixing in the eastern South Indian Ocean using a collection of data from EM-APEX profiling floats, shipboard CTD and microstructure profilers. The floats collected 1566 profiles of temperature, salinity and horizontal velocity data down to 1200 m over a period of about four months. A fine-scale parameterization is applied to the float and CTD data to estimate turbulent mixing. Elevated mixing is observed in the upper ocean, over bottom topography and in mesoscale eddies. Mixing is enhanced in the anticyclonic eddies due to trapped near-inertial waves within the eddy. We found that cyclonic eddies contribute to turbulent mixing in the depth range of 500 – 1000 m, which is associated with downward propagating internal waves. The mean diapycnal diffusivity over 250 – 500 m depth is O(10−6) m2 s−1 and it increases to O(10−5) m2 s−1 in 500 – 1000 m in cyclonic eddies. The turbulent mixing in this region has implications for watermass transformation and large-scale circulation. Higher diffusivity (O(10−5) m2 s−1) is observed in the Antarctic Intermediate Water (AAIW) layer in cyclonic eddies whereas weak diffusivity is observed in the Subantarctic Mode Water (SAMW) layer (O(10−6) m2 s−1). Counter-intuitively, then, the SAMW watermass properties are strongly affected in cyclonic eddies whereas the AAIW layer is less affected. Comparatively high diffusivity at the location of the South Indian Countercurrent (SICC) jets suggests there are wave-mean flow interactions in addition to the wave-eddy interactions that warrant further investigation.

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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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Turbulent Upper-Ocean Mixing Affected by Meltwater Layers during Arctic Summer

Journal of Physical Oceanography ◽

10.1175/jpo-d-16-0200.1 ◽

2017 ◽

Vol 47 (4) ◽

pp. 835-853 ◽

Cited By ~ 18

Author(s):

Achim Randelhoff ◽

Ilker Fer ◽

Arild Sundfjord

Keyword(s):

Surface Layer ◽

Sea Ice ◽

Mixed Layer ◽

Turbulent Mixing ◽

Vertical Structure ◽

Eddy Diffusivity ◽

The Arctic ◽

Vertical Eddy Diffusivity ◽

Vertical Eddy ◽

Arctic Summer

AbstractEvery summer, intense sea ice melt around the margins of the Arctic pack ice leads to a stratified surface layer, potentially without a traditional surface mixed layer. The associated strengthening of near-surface stratification has important consequences for the redistribution of near-inertial energy, ice–ocean heat fluxes, and vertical replenishment of nutrients required for biological growth. The authors describe the vertical structure of meltwater layers and quantify their seasonal evolution and their effect on turbulent mixing in the oceanic boundary layer by analyzing more than 450 vertical profiles of velocity microstructure in the seasonal ice zone north of Svalbard. The vertical structure of the density profiles can be summarized by an equivalent mixed layer depth hBD, which scales with the depth of the seasonal stratification. As the season progresses and melt rates increase, hBD shoals following a robust pattern, implying stronger vertical stratification, weaker vertical eddy diffusivity, and reduced vertical extent of the mixing layer, which is bounded by hBD. Through most of the seasonal pycnocline, the vertical eddy diffusivity scales inversely with buoyancy frequency (Kρ ∝ N−1). The presence of mobile sea ice alters the magnitude and vertical structure of turbulent mixing primarily through stronger and shallower stratification, and thus vertical eddy diffusivity is greatly reduced under sea ice. This study uses these results to develop a quantitative model of surface layer turbulent mixing during Arctic summer and discuss the impacts of a changing sea ice cover.

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