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The mixing layer of Loch Ness

Published online by Cambridge University Press:  19 April 2006

S. A. Thorpe  and
A. J. Hall
S. A. Thorpe
Affiliation:
Institute of Oceanographic Sciences, Wormley, Godalming, Surrey, U.K.
A. J. Hall
Affiliation:
Institute of Oceanographic Sciences, Wormley, Godalming, Surrey, U.K.
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Abstract

Measurements of the thermal and velocity structure of the near-surface mixing layer of a freshwater lake in moderate wind conditions from fixed or mobile arrays of sensors reveal large-scale coherent structures consisting of narrow fronts across which both the temperature and the horizontal component of the current increase. These fronts are generally transverse to the wind direction and are inclined to the vertical, and appear to be similar to fronts, reported as temperature ‘ramps’, in the near-surface atmospheric boundary layer. The time derivatives of the temperature are skewed in a sense consistent with observations in laboratory and atmospheric boundary layers, and of a magnitude consistent with measurements in the latter. Evidence is presented to show that bubbles generated by breaking waves are carried down in the large-scale pattern of flow associated with the fronts in the mixing layer. The presence of a Langmuir circulation associated with wind rows has not been established in these experiments. The relevance of the observations to the ocean mixing layer is discussed.

Type
Research Article
Information
Journal of Fluid Mechanics , Volume 101 , Issue 4 , 29 December 1980 , pp. 687 - 703
Copyright
© 1980 Cambridge University Press

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References

Antonia, R. A., Chambers, A. J., Friehe, C. A. & Van Atta, C. W. 1979 Temperature ramps in the atmospheric surface layer. J. Atmos. Sci. 36, 99–108.Google Scholar
Bradshaw, P. 1967 Inactive motion and pressure fluctuations in turbulent boundary layers. J. Fluid Mech. 30, 241–258.Google Scholar
Browand, F. K. & Winant, C. D. 1973 Laboratory observations of shear-layer instability in a stratified fluid. Boundary-layer Met. 5, 67–78.Google Scholar
Chen, C. H. P. & Blackwelder, R. F. 1978 Large-scale motion in a turbulent boundary layer: a study using temperature contamination. J. Fluid Mech. 89, 1–32.Google Scholar
Dillon, T. M. & Caldwell, D. R. 1978 Catastrophic events in the surface mixed layer. Nature 276, 601–602.Google Scholar
Dillon, T. M. & Powell, T. M. 1976 Low-frequency turbulence spectra in the mixed layer of Lake Tahoe, California—Nevada. J. Geophys. Res. 81, 6421–6427.Google Scholar
Dillon, T. M. & Powell, T. M. 1979 Observations of a surface mixed layer. Deep-Sea Res. 26, 915–932.Google Scholar
Faller, A. J. & Caponi, E. A. 1978 Laboratory studies of wind-driven Langmuir circulations. J. Geophys. Res. 83, 3617–3633.Google Scholar
Garrett, C. J. R. 1976 Generation of Langmuir circulations by surface waves — a feedback mechanism. J. Mar. Res. 34, 117–130.Google Scholar
Gibson, C. H., Friehe, C. A. & McConnell, S. O. 1977 Structure of sheared turbulent fields. Phys. Fluids Suppl. 20, 156–167.Google Scholar
Heathershaw, A. D. 1979 The turbulent structure of the bottom boundary layer in a tidal current. Geophys. J. Roy. Astro. Soc. 58, 395–430.Google Scholar
Jones, I. S. & Kenney, B. C. 1977 The scaling of velocity fluctuations in the surface mixed layer. J. Geophys. Res. 82, 1392–1396.Google Scholar
Kaimal, J. C., Wyngaard, J. C., Izumi, Y. & Coté, O. M. 1972 Spectral characteristics of surface-layer turbulence. Quart. J. Roy. Met. Soc. 98, 563–589.Google Scholar
Kenney, B. C. 1977 An experimental investigation of the fluctuating currents responsible for the generation of windrows. Ph.D. thesis, University of Waterloo.
Labarbera, M. & Vogel, S. 1976 An inexpensive thermistor flow meter for aquatic biology. Limnology & Oceanog. 21, 750–756.Google Scholar
Leibovich, S. 1977 On the evolution of the system of wind drift currents and Langmuir circulations in the ocean. Part I. Theory and averaged current. J. Fluid Mech. 79, 715–743.Google Scholar
Leibovich, S. & Radhakrishnan, K. 1977 On the evolution of the system of wind drift currents and Langmuir circulations in the ocean. Part II. Structure of Langmuir vortices. J. Fluid Mech. 80, 481–507.Google Scholar
Murray, J. & Puller, L. 1910 Bathymetrical survey of the Scottish fresh-water lochs during the years 1897–1909. Report of the Scientific Results, vols. 1–6. Edinburgh: Challenger Office.
Phong-Anant, D., Antonia, R. A., Chambers, A. J. & Rajagopalan, S. 1980 Features of the large scale motion in the atmospheric surface layer. (submitted to J. Geophys. Res.)Google Scholar
Pollard, R. T. 1977 Observations and theories of Langmuir circulations and their role in near surface mixing. In A Voyage of Discovery, G. Deacon 70th anniversary vol. (ed. M. Angel). Pergamon.
Riedl, R. J. & Machan, R. 1972 Hydrodynamic patterns in the lotic inter-tidal sands and their bioclimatological implications. Mar. Biol. 13, 179–209.Google Scholar
Scott, J. T., Myer, G. E., Stewart, R. & Walther, E. G. 1969 On the mechanism of Langmuir circulations and their role in epilimnion mixing. Limnology & Oceanog. 14, 493–503.Google Scholar
Sreenivasan, K. R. & Antonia, R. A. 1977 Skewness of temperature derivations in turbulent shear flows. Phys. Fluids 20, 1986–1988.Google Scholar
Stewart, R. W. & Grant, H. L. 1962 Determination of the rate of dissipation of turbulent energy near the sea surface in the presence of waves. J. Geophys. Res. 67, 3177–3180.Google Scholar
Thorpe, S. A. 1971 Experiments on the instability of stratified shear flows: miscible fluids. J. Fluid Mech. 46, 299–319.Google Scholar
Thorpe, S. A. 1977 Turbulence and mixing in a Scottish loch. Phil. Trans. Roy. Soc. A 286, 125–181.Google Scholar
Thorpe, S. A. 1978a The near-surface ocean mixing layer in stable heating conditions. J. Geophys. Res. 83, 2875–2885.Google Scholar
Thorpe, S. A. 1978b On internal gravity waves in an accelerating shear flow. J. Fluid Mech. 88, 623–639.Google Scholar
Thorpe, S. A. & Hall, A. J. 1977 Mixing in upper layer of a lake during heating cycle. Nature 265, 719–722.Google Scholar
Thorpe, S. A., Hall, A. J., Taylor, C. & Allen, J. 1977 Billows in Loch Ness. Deep-Sea Res. 24, 371–379.Google Scholar
Thorpe, S. A. & Humphries, P. N. 1980 Bubbles and breaking waves. Nature 283, 463–465.Google Scholar
Thorpe, S. A. & Stubbs, A. R. 1979 Bubbles in a freshwater lake. Nature 279, 403–405.Google Scholar
Weinstock, J. 1978 Vertical turbulent diffusion in a stably stratified fluid. J. Atmos. Sci. 35, 1022–1027.Google Scholar