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S. A. Thorpe, M. S. Cure, A. Graham, and A. J. Hall

OCTOBER 1994 THORPE ET AL. 1273Sonar Observations of Langmuir Circulation and Estimation of Dispersion of Floating Particles S. A. THORPE, M. S. CURE,* AND A. GRAHAMDepartment of Oceanography, University of ~outhampton, Southampton, United Kingdom A. J. HALLInstitute of Oceanographic Sciences Deacon Laboratory, Wormley, Godalming, Surrey, United

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S. A. Thorpe, M. J. Ulloa, D. Baldwin, and A. J. Hall

1. Introduction The use of upward-pointing sonar as a means to investigate the upper ocean has developed rapidly in the last 15 years. It has proved to be a useful means of collecting information about surface waves, particularly their breaking and the bubble clouds they create, surface currents, internal waves, and Langmuir circulation (see, e.g., Thorpe and Hall 1983 ; Zedel and Farmer 1991 ). Many of the observations, however, are restricted by the lack of a system with independent power

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Antony K. Liu, Seelye Martin, and Ronald Kwok

. Lawrence Island polynya. The young ice area of polynya within each SAR image can be estimated and its growth rate is found to be 2.52 exp(day/3.36). b. The active polynya region For the active polynya region on 27 February, Fig. 5 shows the long, linear streaks characteristic of the Langmuir circulation and its 2D FFT. The transformed image in Fig. 5b shows that the Langmuir cells have many scales with one peak at 120 m and another at approximately 230 m. Figure 6 shows the use of this Fourier and

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Jerome A. Smith

1969 ; Longuet-Higgins 1970a , b ); the interaction of freely propagating long and short surface waves ( Longuet-Higgins 1969 ; Hasselmann 1971 ; Garrett and Smith 1976 ; and many others); and the generation of Langmuir circulation (LC), a prominent form of motion in the wind-driven surface mixed layer (e.g., Langmuir 1938 ; Craik 1977 ; Leibovich 1980 ; Li et al. 1995 ; Skyllingstad and Denbo 1995 ; McWilliams et al. 1997 ; McWilliams and Sullivan 2000 ; Phillips 2002 ; Sullivan et al

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Luc Lenain and W. Kendall Melville

. 2003 ). Measuring the evolution of the wave directional spectrum in a tropical storm is critical for improving hurricane intensity forecasts, as the Stokes drift of the surface wave field interacting with the vorticity of surface shear currents produces Langmuir circulations (LCs) through the vortex force of the Craik–Leibovich theory ( Craik and Leibovich 1976 ). LCs contribute to the mixing of the upper ocean and hence to the enthalpy transfer between the ocean and the atmosphere ( Sullivan and

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Ann E. Gargett and Dana K. Savidge

initial impetus for this work was to determine the effect of a dominant semidiurnal tide on Langmuir circulations, further separation of inertial oscillations from tidal signals was not carried out. Should such separation be required, rotary methods exist (spectral and empirical orthogonal function analysis), subject to the standard limitations imposed on spectral accuracy by record length ( Gonella 1972 ; Denbo and Allen 1984 ). In what follows, the use of the terms fluctuation , tide , and mean

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Xuefeng Zhang, Guijun Han, Dong Li, Xinrong Wu, Wei Li, and Peter C. Chu

1. Introduction Observations ( Kitaigorodskii and Lumley 1983 ; Thorpe 1984 ; Anis and Moum 1992 ; Terray et al. 1996 ; Drennan et al. 1996 ; Babanin 2006 ; Kantha et al. 2010 ) show that the dissipation of turbulent kinetic energy (TKE) is enhanced greatly near the sea surface by surface gravity waves under nonbreaking (including nonbreaking wave turbulence and Langmuir turbulence) and breaking waves. The breaking-wave-induced mixing has been broadly implemented into ocean circulation

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P. Wadhams, J. P. Wilkinson, and A. Kaletzky

1. Introduction Recent evidence of changes in the Arctic indicate that the sea ice cover is undergoing a significant thinning ( Rothrock et al. 1999 ; Wadhams and Davis 2000 ) and retreat (e.g., Bjørgo et al. 1997 ). General circulation models using greenhouse gas forcing predict that the Arctic ice cover will continue to diminish because of global warming and may become seasonal by the 2080s. At the same time, it is possible that the current ice shrinkage is a response to oceanic and

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W. Kendall Melville, Luc Lenain, Daniel R. Cayan, Mati Kahru, Jan P. Kleissl, P. F. Linden, and Nicholas M. Statom

aligned in the northeast–southwest direction. These are believed to be the surface signatures of Langmuir circulation (or Langmuir turbulence) that are approximately aligned with the wind and the direction of dominant wave propagation. (b),(c) Evolution of the omnidirectional wavenumber spectrum as the aircraft flew across the Loop Current. The color scale represents the average SST over the length of the wave record (4 km) used in the spectral analysis, also shown as a function of latitude in (b). d

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Len Zedel

Langmuir circulation, air-sea momentum and gasexchange, and wave breaking. A supplementary observation required for any of these studies is the surfacewave condition prevailing at the time of the acousticobservations. An obvious way to acquire wave-heightdata for such acoustically based studies is to use vertically oriented sonar to measure local sea surface elevations directly: this can be achieved by recording atime series of surface range estimates. Thorpe and Hall(1983) noted the possibility for

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