Hostname: page-component-cd9895bd7-jkksz Total loading time: 0 Render date: 2024-12-26T07:54:19.009Z Has data issue: false hasContentIssue false
  • English
  • Français

Observations of the thermal structure of Langmuir circulation

Published online by Cambridge University Press:  20 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.
Get access Rights & Permissions [Opens in a new window]

Abstract

A near-vertical array of thermistors has been towed through the water beneath several hundred well-defined wind rows formed on the surface of a fresh-water loch in winds of 7–9 m s−1. The loch was stably stratified in the mean, temperatures decreasing with depth, and the air warmer than the water. The temperatures at ten levels in the water and the positions of the wind rows were recorded. These measurements were supplemented by photographs of the wind rows and observations of bubbles, using sonar.

The data has been analysed to produce average temperature sections across the wind rows. Near the surface a core of warm water can be distinguished beneath the wind row in the average section (although not in general in the unaveraged records) and colder water between rows, consistent with there being a Langmuir circulation pattern. At depths greater than about 0·4 times the average distances between rows, it is, however, apparent that the temperature anomalies slope to the left of the wind direction as depth increases.

The anomalies (although generally significantly different from the mean) are much less than the standard deviation of the local fluctuations in loch temperature and also much smaller than the temperature changes at the ‘ramps’ described earlier (Thorpe & Hall 1980), here observed to extend to within 0·4 m of the surface. There are thus two co-existing, but possibly independent, thermal structures which can be recognized in the turbulent mixing layer.

Type
Research Article
Information
Journal of Fluid Mechanics , Volume 114 , January 1982 , pp. 237 - 250
Copyright
© 1972 Cambridge University Press

Access options

Get access to the full version of this content by using one of the access options below. (Log in options will check for institutional or personal access. Content may require purchase if you do not have access.)

References

Craik, A. D. D. 1977 The generation of Langmuir circulations by an instability mechanism. J. Fluid Mech. 81, 209–223.Google Scholar
Craik, A. D. D. & Leibovich, S. 1976 A rational model for Langmuir circulations. J. Fluid Mech. 73, 401–426.Google Scholar
Faller, A. J. 1971 Oceanic turbulence and the Langmuir circulations. Ann. Rev. Ecology & Systematics 2, 201–236.Google Scholar
Faller, A. J. & Caponi, E. A. 1978 Laboratory studies of wind driven Langmuir circulations. J. Geophys. Res. 83, 3617–3633.Google Scholar
Faller, A. J. & Kaylor, R. E. 1966 A numerical study of the instability of the laminar Ekman boundary layer. J. Atmos. Sci. 23, 466–480.Google Scholar
Langmuir, I. 1938 Surface water motion induced by wind. Science 87, 119–123.Google Scholar
Leibovich, S. 1977a On the evolution of the system of wind drift currents and Langmuir circulations in the ocean. Part 1. Theory and averaged current. J. Fluid Mech. 79, 715–743.Google Scholar
Leibovich, S. 1977b Convective instability of stably stratified water in the ocean. J. Fluid Mech. 82, 561–585.Google Scholar
Leibovich, S. 1980 On wave — current interaction theories of Langmuir circulation. J. Fluid Mech. 99, 715–724.Google Scholar
Leibovich, S. & Paolucci, S. 1980 The Langmuir circulation instability as a mixing mechanism in the upper ocean. J. Phys. Oceanog. 10, 186–207.Google Scholar
Leibovich, S. & Radhakrishnan, K. 1977 On the evolution of the system of wind drift currents and Langmuir circulations in the ocean. Part 2. Structure of the Langmuir vortices. J. Fluid Mech. 80, 481–507.CrossRefGoogle Scholar
Mcleish, W. 1968 On the mechanism of wind-slick generation. Deep-Sea Res. 15, 461–469.Google Scholar
Mcleish, W. 1970 Spatial spectra of ocean surface temperature. J. Geophys. Res. 75, 6872–6877.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 Volume (ed. M. Angel), pp. 235–251. Pergamon.
Saunders, P. M. 1967 The temperature at the ocean — air interface. J. Atmos. Sci. 24, 269–273.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. Limnol. Oceanog. 14, 493–503.Google Scholar
Simpson, J. H. & Woods, J. D. 1970 Temperature microstructure in a freshwater thermocline. Nature 226, 832–834.Google Scholar
Thorpe, S. A. 1977 Turbulence and mixing in a Scottish loch. Phil. Trans. R. Soc. Lond. A 286, 125–181.Google Scholar
Thorpe, S. A. 1978 The near-surface ocean mixing layer in stable heating conditions. J. Geophys. Res. 83, 2875–2885.Google Scholar
Thorpe, S. A. & Hall, A. J. 1980 The mixing layer of Loch Ness. J. Fluid Mech. 101, 687–703.Google Scholar
Thorpe, S. A. & Humphries, P. H. 1980 Bubbles and breaking waves. Nature 283, 463–465.Google Scholar
Thorpe, S. A. & Stubes, A. R. 1979 Bubbles in a freshwater lake. Nature 279, 403–405.Google Scholar
Wedderburn, E. M. 1907 The temperatures of the fresh water lochs of Scotland, with special reference to Loch Ness. Trans. R. Soc. Edin. 45, 407–489.Google Scholar