• Batchelor, G. K., 1959: Small-scale variation of convected quantities like temperature in turbulent fluid. J. Fluid Mech., 5, 113–133, https://doi.org/10.1017/S002211205900009X.

    • Search Google Scholar
    • Export Citation
  • Bhat, G. S., and Coauthors, 2001: BOBMEX: The Bay of Bengal Monsoon Experiment. Bull. Amer. Meteor. Soc., 82, 22172243, https://doi.org/10.1175/1520-0477(2001)082<2217:BTBOBM>2.3.CO;2.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Chen, G., W. Han, Y. Li, M. J. McPhaden, J. Chen, W. Wang, and D. Wang, 2017: Strong intraseasonal variability of meridional currents near 5°N in the eastern Indian Ocean: Characteristics and causes. J. Phys. Oceanogr., 47, 979998, https://doi.org/10.1175/JPO-D-16-0250.1.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Cherian, D. A., E. L. Shroyer, H. W. Wijesekera, and J. N. Moum, 2020: The seasonal cycle of upper-ocean mixing at 8°N in the Bay of Bengal. J. Phys. Oceanogr., 50, 323342, https://doi.org/10.1175/JPO-D-19-0114.1.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Cullen, K. E., and E. L. Shroyer, 2019: Seasonality and interannual variability of the Sri Lanka dome. Deep-Sea Res. II, 168, 104642, https://doi.org/10.1016/j.dsr2.2019.104642.

    • Search Google Scholar
    • Export Citation
  • Dillon, T. M., and D. R. Caldwell, 1980: The Batchelor spectrum and dissipation in the upper ocean. J. Geophys. Res., 85, 19101916, https://doi.org/10.1029/JC085iC04p01910.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Goodman, L., E. R. Levine, and R. G. Lueck, 2006: On measuring the terms of the turbulent kinetic energy budget from an AUV. J. Atmos. Oceanic Technol., 23, 977990, https://doi.org/10.1175/JTECH1889.1.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Gregg, M. C., 1989: Scaling turbulent dissipation in the thermocline. J. Geophys. Res., 94, 96869698, https://doi.org/10.1029/JC094iC07p09686.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Gregg, M. C., and T. B. Sanford, 1988: The dependence of turbulent dissipation on stratification in a diffusively stable thermocline. J. Geophys. Res., 93, 12 38112 392, https://doi.org/10.1029/JC093iC10p12381.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Gregg, M. C., E. A. D’Asaro, J. J. Riley, and E. Kunze, 2018: Mixing efficiency in the ocean. Annu. Rev. Marine Sci., 10, 443473, https://doi.org/10.1146/annurev-marine-121916-063643.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Jensen, T. G., H. W. Wijesekera, E. S. Nyadjro, P. G. Thoppil, J. F. Shriver, K. K. Sandeep, and V. Pant, 2016: Modeling salinity exchanges between the equatorial Indian Ocean and the Bay of Bengal. Oceanography, 29 (2), 92101, https://doi.org/10.5670/oceanog.2016.42.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Jensen, T. G., J. Magalhães, H. W. Wijesekera, M. Buijsman, R. Helber, and J. Richman, 2020: Numerical modelling of tidally generated internal wave radiation from the Andaman Sea into the Bay of Bengal. Deep-Sea Res. II, 172, 104710, https://doi.org/10.1016/j.dsr2.2019.104710.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Jinadasa, S. U. P., I. Lozovatsky, J. Planella-Morató, J. D. Nash, J. A. MacKinnon, A. J. Lucas, H. W. Wijesekera, and H. J. S. Fernando, 2016: Ocean turbulence and mixing around Sri Lanka and in adjacent waters of the northern Bay of Bengal. Oceanography, 29 (2), 170179, https://doi.org/10.5670/oceanog.2016.49.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Kumar, B. P., J. Vialard, M. Lengaigne V. S. N. Murty, and M. J. McPhaden, 2012: TropFlux: Air-sea fluxes for the global tropical oceans—Description and evaluation. Climate Dyn., 38, 15211543, https://doi.org/10.1007/s00382-011-1115-0.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Kunze, E., 2017: Internal-wave-driven mixing: Global geography and budgets. J. Phys. Oceanogr., 47, 13251345, https://doi.org/10.1175/JPO-D-16-0141.1.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Kunze, E., R. W. Schmitt, and J. M. Toole, 1995: The energy balance in a warm-core ring’s near-inertial critical layer. J. Phys. Oceanogr., 25, 942957, https://doi.org/10.1175/1520-0485(1995)025<0942:TEBIAW>2.0.CO;2.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Kunze, E., E. Firing, J. M. Hummon, T. K. Chereskin, and A. M. Thurnherr, 2006: Global abyssal mixing inferred from lowered ADCP shear and CTD strain profiles. J. Phys. Oceanogr., 36, 15531576, https://doi.org/10.1175/JPO2926.1.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Lozovatsky, I., H. Wijesekera, E. Jarosz, M.-J. Lilover, A. Pirro, Z. Silver, L. Centurioni, and H. J. S. Fernando, 2016: A snapshot of internal waves and hydrodynamic instabilities in the southern Bay of Bengal. J. Geophys. Res. Oceans, 121, 58985915, https://doi.org/10.1002/2016JC011697.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Lozovatsky, I., A. Pirro, E. Jarosz, H. W. Wijesekera, S. U. P. Jinadasa, and H. J. S. Fernando, 2019: Turbulence at the periphery of Sri Lanka dome. Deep-Sea Res. II, 168, 104614, https://doi.org/10.1016/j.dsr2.2019.07.002.

    • Search Google Scholar
    • Export Citation
  • Lueck, R. G., 2016: Calculating the rate of dissipation of turbulent kinetic energy. Rockland Scientific International Tech. Note 028, 19 pp., https://rocklandscientific.com/support/knowledge-base/technical-notes/.

  • Lueck, R. G., F. Wolk, J. Hancyck, and K. Black, 2015: Hub-height time series measurements of velocity and dissipation of turbulence kinetic energy in a tidal channel, IEEE/OES 11th Current, Waves and Turbulence Measurement, St. Petersburg, FL, IEEE, https://doi.org/10.1109/CWTM.2015.7098143.

    • Crossref
    • Export Citation
  • Moum, J. N., and J. D. Nash, 2009: Mixing measurements on an equatorial ocean mooring. J. Atmos. Oceanic Technol., 26, 317336, https://doi.org/10.1175/2008JTECHO617.1.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Nasmyth, P. W., 1970: Oceanic turbulence. Ph.D. thesis, Institute of Oceanography, University of British Columbia, 106 pp.

  • Osborn, T. R., 1974: Vertical profiling of velocity microstructure. J. Phys. Oceanogr., 4, 109115, https://doi.org/10.1175/1520-0485(1974)004<0109:VPOVM>2.0.CO;2.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Osborn, T. R., 1980: Estimates of the local rate of vertical diffusion from dissipation measurements. J. Phys. Oceanogr., 10, 8389, https://doi.org/10.1175/1520-0485(1980)010<0083:EOTLRO>2.0.CO;2.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Osborn, T. R., and C. S. Cox, 1972: Oceanic fine structure. Geophys. Fluid Dyn., 3, 321345, https://doi.org/10.1080/03091927208236085.

  • Pirro, A., H. J. S. Fernando, H. W. Wijesekera, T. G. Jensen, L. R. Centurioni, and S. U. P. Jinadasa, 2020a: Eddies and currents in the Bay of Bengal during summer monsoons. Deep-Sea Res. II, 172, 104728, https://doi.org/10.1016/j.dsr2.2019.104728.

    • Search Google Scholar
    • Export Citation
  • Pirro, A., H. W. Wijesekera, E. Jarosz, and H. J. S. Fernando, 2020b: Dynamics of intraseasonal oscillations in the Bay of Bengal during summer monsoons captured by mooring observations. Deep-Sea Res. II, 172, 104718, https://doi.org/10.1016/j.dsr2.2019.104718.

    • Search Google Scholar
    • Export Citation
  • Polzin, K. L., 2010: Mesoscale eddy–internal wave coupling. Part II: Energetics and results from PolyMode. J. Phys. Oceanogr., 40, 789801, https://doi.org/10.1175/2009JPO4039.1.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Polzin, K. L., J. M. Toole, and R. W. Schmitt, 1995: Finescale parameterizations of turbulent dissipation. J. Phys. Oceanogr., 25, 306328, https://doi.org/10.1175/1520-0485(1995)025<0306:FPOTD>2.0.CO;2.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Rao, S. A., and Coauthors, 2011: Modulation of SST, SSS over northern Bay of Bengal on ISO time scale. J. Geophys. Res., 116, C09026, https://doi.org/10.1029/2010JC006804.

    • Search Google Scholar
    • Export Citation
  • Ruddick, B., 1983: A practical indicator of the stability of the water column to double-diffusive activity. Deep-Sea Res., 30, 11051107, https://doi.org/10.1016/0198-0149(83)90063-8.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Schott, F., and J. P. McCreary, 2001: The monsoon circulation of the Indian Ocean. Prog. Oceanogr., 51, 1123, https://doi.org/10.1016/S0079-6611(01)00083-0.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • St. Laurent, L., and S. Merrifield, 2017: Measurements of near-surface turbulence and mixing from autonomous ocean gliders. Oceanography, 30 (2), 116125, https://doi.org/10.5670/oceanog.2017.231.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Thakur, R., E. L. Shroyer, R. Govindarajan, J. T. Farrar, R. A. Weller, and J. N. Moum, 2019: Seasonality and buoyancy suppression of turbulence in the Bay of Bengal. Geophys. Res. Lett., 46, 43464355, https://doi.org/10.1029/2018GL081577.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Torrence, C., and G. P. Compo, 1998: A practical guide to wavelet analysis. Bull. Amer. Meteor. Soc., 79, 6178, https://doi.org/10.1175/1520-0477(1998)079<0061:APGTWA>2.0.CO;2.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Vinayachandran, P. N., and T. Yamagata, 1998: Monsoon response of the sea around Sri Lanka: Generation of thermal domes and anticyclonic vortices. J. Phys. Oceanogr., 28, 19461960, https://doi.org/10.1175/1520-0485(1998)028<1946:MROTSA>2.0.CO;2.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Vinayachandran, P. N., D. Shankar, S. Vernekar, K.K. Sandeep, P. Amol, C.P. Neema, and A. Chatterjee, 2013: A summer monsoon pump to keep the Bay of Bengal salty. Geophys. Res. Lett., 40, 17771782, https://doi.org/10.1002/grl.50274.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Vinayachandran, P. N., and Coauthors, 2018: BOBBLE: Ocean–atmosphere interaction and its impact on the South Asian monsoon. Bull. Amer. Meteor. Soc., 99, 15691587, https://doi.org/10.1175/BAMS-D-16-0230.1.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Warner, S. J., J. Becherer, K. Pujiana, E. L. Shroyer, M. Ravichandran, V. P. Thangaprakash, and J. N. Moum, 2016: Monsoon mixing cycles in the Bay of Bengal: A year-long subsurface mixing record. Oceanography, 29 (2), 158169, https://doi.org/10.5670/oceanog.2016.48.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Webber, B. G. M., A. J. Matthews, P. N. Vinayachandran, C. P. Neema, A. Sanchez-Franks, V. Vijith, P. Amol, and D. B. Baranowski, 2018: The dynamics of the Southwest Monsoon Current in 2016 from high-resolution in situ observations and models. J. Phys. Oceanogr., 48, 22592282, https://doi.org/10.1175/JPO-D-17-0215.1.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Webster, P. J., and Coauthors, 2002: The JASMINE pilot study. Bull. Amer. Meteor. Soc., 83, 16031630, https://doi.org/10.1175/BAMS-83-11-1603.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Whalen, C. B., J. A. MacKinnon, L. D. Talley, and A. F. Waterhouse, 2015: Estimating the mean diapycnal mixing using a finescale strain parameterization. J. Phys. Oceanogr., 45, 11741188, https://doi.org/10.1175/JPO-D-14-0167.1.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Wijesekera, H., L. Padman, T. Dillon, M. Levine, C. Paulson, and R. Pinkel, 1993: The application of internal-wave dissipation models to a region of strong mixing. J. Phys. Oceanogr., 23, 269286, https://doi.org/10.1175/1520-0485(1993)023<0269:TAOIWD>2.0.CO;2.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Wijesekera, H., and Coauthors, 2016a: ASIRI: An ocean–atmosphere initiative for Bay of Bengal. Bull. Amer. Meteor. Soc., 97, 18591884, https://doi.org/10.1175/BAMS-D-14-00197.1.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Wijesekera, H., W. J. Teague, D. W. Wang, E. Jarosz, and T. G. Jenson, 2016b: Low-frequency currents from deep moorings in the southern Bay of Bengal. J. Phys. Oceanogr., 46, 32093238, https://doi.org/10.1175/JPO-D-16-0113.1.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Wijesekera, H. W., W. J. Teague, E. Jarosz, D. W. Wang, H. J. S. Fernando, and Z. R. Hallock, 2019: Internal tidal currents and solitons in the southern Bay of Bengal. Deep-Sea Res. II, 168, 104587, https://doi.org/10.1016/j.dsr2.2019.05.010.

    • Search Google Scholar
    • Export Citation
  • Wolk, F., H. Yamazaki, L. Seuront, and R. G. Lueck, 2002: A new free-fall profiler for measuring biophysical microstructure. J. Atmos. Oceanic Technol., 19, 780793, https://doi.org/10.1175/1520-0426(2002)019<0780:ANFFPF>2.0.CO;2.

    • Crossref
    • Search Google Scholar
    • Export Citation
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Observations of Eddy-Modulated Turbulent Mixing in the Southern Bay of Bengal

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  • 1 a Naval Research Laboratory, Stennis Space Center, Mississippi
  • | 2 b Ocean University, Colombo, Sri Lanka
  • | 3 c Department of Civil and Environmental Engineering and Earth Sciences, University of Notre Dame, Notre Dame, Indiana
  • | 4 d SRR International, Inc., Riviera Beach, Florida
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Abstract

Long-term measurements of turbulent kinetic energy dissipation rate (ε), and turbulent temperature variance dissipation rate (χT) in the thermocline, along with currents, temperature, and salinity were made at two subsurface moorings in the southern Bay of Bengal (BoB). This is a part of a major international program, conducted between July 2018 and June 2019, for investigating the role of the BoB on the monsoon intraseasonal oscillations. One mooring was located on the typical path of the Southwest Monsoon Current (SMC), and the other was in a region where the Sri Lanka dome is typically found during the summer monsoon. Microstructure and finescale estimates of vertical diffusivity revealed the long-term subthermocline mixing patterns in the southern BoB. Enhanced turbulence and large eddy diffusivities were observed within the SMC during the passage of a subsurface-intensified anticyclonic eddy. During this time, background shear and strain appeared to influence high-frequency motions such as near-inertial waves and internal tides, leading to increased mixing. Near the Sri Lanka dome, enhanced dissipation occurred at the margins of the cyclonic feature. Turbulent mixing was enhanced with the passage of Rossby waves and eddies. During these events, values of χT exceeding 10−4 °C2 s−1 were recorded concurrently with ε values exceeding 10−5 W kg−1. Inferred diffusivity peaked well above background values of 10−6 m2 s−1, leading to an annually averaged diffusivity near 10−4 m2 s−1. Turbulence appeared low throughout much of the deployment period. Most of the mixing occurred in spurts during isolated events.

This article is included in the Air–sea interactions during PISTON, MISOBOB, and CAMP2Ex Special Collection.

© 2021 American Meteorological Society. For information regarding reuse of this content and general copyright information, consult the AMS Copyright Policy (www.ametsoc.org/PUBSReuseLicenses).

Corresponding author: Conrad A. Luecke, conrad.luecke.ctr@nrlssc.navy.mil

Abstract

Long-term measurements of turbulent kinetic energy dissipation rate (ε), and turbulent temperature variance dissipation rate (χT) in the thermocline, along with currents, temperature, and salinity were made at two subsurface moorings in the southern Bay of Bengal (BoB). This is a part of a major international program, conducted between July 2018 and June 2019, for investigating the role of the BoB on the monsoon intraseasonal oscillations. One mooring was located on the typical path of the Southwest Monsoon Current (SMC), and the other was in a region where the Sri Lanka dome is typically found during the summer monsoon. Microstructure and finescale estimates of vertical diffusivity revealed the long-term subthermocline mixing patterns in the southern BoB. Enhanced turbulence and large eddy diffusivities were observed within the SMC during the passage of a subsurface-intensified anticyclonic eddy. During this time, background shear and strain appeared to influence high-frequency motions such as near-inertial waves and internal tides, leading to increased mixing. Near the Sri Lanka dome, enhanced dissipation occurred at the margins of the cyclonic feature. Turbulent mixing was enhanced with the passage of Rossby waves and eddies. During these events, values of χT exceeding 10−4 °C2 s−1 were recorded concurrently with ε values exceeding 10−5 W kg−1. Inferred diffusivity peaked well above background values of 10−6 m2 s−1, leading to an annually averaged diffusivity near 10−4 m2 s−1. Turbulence appeared low throughout much of the deployment period. Most of the mixing occurred in spurts during isolated events.

This article is included in the Air–sea interactions during PISTON, MISOBOB, and CAMP2Ex Special Collection.

© 2021 American Meteorological Society. For information regarding reuse of this content and general copyright information, consult the AMS Copyright Policy (www.ametsoc.org/PUBSReuseLicenses).

Corresponding author: Conrad A. Luecke, conrad.luecke.ctr@nrlssc.navy.mil
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