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Lozovatsky I.,University of Notre Dame | Lee J.-H.,Korea Advanced Institute of Science and Technology | Fernando H.J.S.,University of Notre Dame | Kang S.K.,Korea Advanced Institute of Science and Technology | Jinadasa S.U.P.,National Aquatic Resources Research and Development Agency
Journal of Geophysical Research C: Oceans | Year: 2015

A series of 134 microstructure profiles were taken in the central East China Sea from a drifting ship, covering more than 12 miles over the sloping bottom. The water depth z varied in the range 52-62 m; the tidal elevation of semidiurnal component was ±1 m. Prior to the onset of 25 h drift, a hydrographic section consisting of 9 stations, 15 miles apart, was taken in the area. A shallow mixed surface layer (SL) underlain by a diurnal pycnocline (z < 13 m), a sharp thermohalocline (13 < z < 30 m), and about 20 m tall bottom boundary layer (BBL) were the main features of summertime stratification. The splitting of upper pycnocline by a warmer, saltier intrusion led to the generation of turbulent patches at the lower, but not at the upper, density interface of this water body, suggesting asymmetry of mixing across the intrusion. In a limited range of the normalized squared buoyancy frequency, 2


Jinadasa S.U.P.,National Aquatic Resources Research and Development Agency | Lozovatsky I.,University of Notre Dame | Planella-Morato J.,University of Notre Dame | Planella-Morato J.,University of Girona | And 5 more authors.
Oceanography | Year: 2016

As a part of the US Air-Sea Interactions Regional Initiative, the first extensive set of turbulent kinetic energy dissipation rate (ε) measurements from microstructure profilers were obtained in the Bay of Bengal (BoB) and around Sri Lanka during 2013–2015. The observations span almost 1,200 km meridionally, and capture the dynamics associated with a variety of mesoscale and submesoscale features. High freshwater input in the northern part of the basin leads to regions of intense near-surface stratification, which become weaker moving south. The thin layers trap mechanical energy input from the atmosphere, often confining turbulence to the surface boundary layer. These thin layers can form shallow fronts, which at times resemble turbulent gravity currents (Sarkar et al., 2016, in this issue), and are associated with high levels of mixing. Away from the local frontal zones, turbulence in the surface low-salinity layer appears to be decoupled from the underlying pycnocline, where turbulence occurs only in rare and sporadic breaking events. A striking feature common to all of the data acquired is a dearth of turbulent mixing at depth, a condition that appears to be pervasive throughout the basin except during the passage of tropical storms. It is likely that the strong near-surface stratification effectively isolates the deeper water column from mechanical penetration of atmospheric energy. © 2016 by The Oceanography Society. All rights reserved.


Wijesekera H.W.,U.S. Navy | Teague W.J.,U.S. Navy | Jarosz E.,U.S. Navy | Wang D.W.,U.S. Navy | And 7 more authors.
Oceanography | Year: 2016

Long-term time series of velocity, hydrographic, and turbulence fields were collected from a six-element subsurface mooring array in the southern Bay of Bengal. The moorings, deployed in December 2013 and recovered in August 2015, were entangled with commercial fishing nets and lines, while top subsurface buoys ended up being serendipitously closer to the surface than planned. In spite of these unexpected events, almost all the sensors and data were recovered. The moorings provided currents between 6 m and 500 m depths from acoustic Doppler current profilers, supplemented by hydrographic data and turbulent dissipation rates at selected depths. The observations captured the summer and winter monsoon currents, eddies, and intraseasonal oscillations. Near-surface currents as large as 1.75 m s–1 were observed in July 2014. Currents stronger than 0.5 m s–1 were confined to the upper 200 m. Observations of currents, temperature, and sea surface height (SSH) fields revealed eddylike features with positive and negative SSH anomalies (~20 cm) moving westward at speeds of about 0.1 m s–1. Intraseasonal oscillations with periods of 30 to 90 days were strongest near the surface. For the duration of the deployment, root-mean-square velocity fluctuations were about 0.1 m s–1 near the surface but decayed with depth and became nearly uniform (~0.03–0.06 m s–1) below 100 m. © 2016 by The Oceanography Society. All rights reserved.


Lee C.M.,University of Washington | Jinadasa S.U.P.,National Aquatic Resources Research and Development Agency | Anutaliya A.,University of California at San Diego | Centurioni L.R.,University of California at San Diego | And 6 more authors.
Oceanography | Year: 2016

The region surrounding Sri Lanka modulates monsoon-driven exchange between the Bay of Bengal and the Arabian Sea. Here, local circulation impacts the pathways followed by the boundary currents that drive exchange, thereby modulating mixing and water mass transformation. From 2013 to 2016, an international partnership conducted sustained measurements around the periphery of Sri Lanka, with the goal of understanding how circulation and mixing in this critical region modulate exchange between the Bay of Bengal and the Arabian Sea. Observations from satellite remote sensing, surface drifters, gliders, current meter moorings, and Pressure Inverted Echo Sounders capture seasonally reversing monsoon currents off the southern tip of Sri Lanka, trace the wintertime freshwater export pathway of the East India Coastal Current, and document the deflection of currents running along the east coast of Sri Lanka by cyclonic and anticyclonic eddies. Measurements also reveal energetic interleaving, indicative of mixing and stirring associated with these flows. Circulation inferred from satellite remote sensing and drifter tracks sometimes differs from that indicated by in situ sections, pointing to the need for observing systems that employ complementary approaches toward understanding this region. © 2016 by The Oceanography Society. All rights reserved.


Jinadasa S.U.P.,National Aquatic Resources Research and Development Agency | Lozovatsky I.D.,University of Notre Dame | Fernando H.J.S.,University of Notre Dame
Physica Scripta | Year: 2013

The intermittency correction factor μc for the Obukhov-Corrsin ' - 5/3' inertial-convective subrange spectral law is estimated using conductivity (temperature) fluctuation measurements conducted within the microstructure patches of oceanic pycnocline in Monterey Bay. The value of μc was found to be in the range of 0.46-0.51, depending on the accuracy of calculation, which is applicable to stratified, low-Reynolds-number oceanic turbulence. The intermittency factor μM c for mesoscale (up to 1 km) lateral variations of scalar dissipation is estimated as 0.43 ± 0.02. The breakdown mechanisms of small-scale locally isotropic and mesoscale non-isotropic (lateral) turbulent temperature fluctuations in oceanic turbulence are discussed in the light of the above observations. © 2013 The Royal Swedish Academy of Sciences.

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