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Michael C. Gregg and John K. Horne

-dimensional effects due to substantially weakened tail vortices, resulting in a reverse von Kármán vortex street. Flow around the fish is dominantly two-dimensional, and the vortices shed from its tail are nearly vertical when the fish swims horizontally. 3. Acoustic characterization of aggregation backscatter Because tidal currents produce or affect most mixing in shallow water, we surveyed mixing in Monterey Bay by repeating slow, ≈1 m s −1 , transects along survey lines for 12.5 h, the period of the twice

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Ming Li, Svein Vagle, and David M. Farmer

mechanically driven system with four sidescan sonars, Farmer and Li (1995) examined time sequences of horizontal backscatter images and found that some bubble bands join together to form Y-shaped junctions at high winds. These acoustic measurements capture the spatial structures and temporal evolutions of turbulence flows in the OML and provide useful data for comparing with LES simulation results. Smith (1992) observed a rapid evolution of LC from small to large scales, following a sudden increase in

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Maxim Nikurashin and Raffaele Ferrari

motions are very efficient at radiating waves from small topographic features, resulting in local mixing. Polzin and Firing (1997) also found that abyssal mixing appears to be enhanced in regions of strong geostrophic flows. Here, we test the hypothesis that the abyssal mixing observed in the Southern Ocean can be explained by radiation and breaking of waves resulting from geostrophic flows impinging on small-scale topography. Estimates of turbulent mixing inferred from lowered acoustic Doppler

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Alexander Minakov, Henk Keers, Dmitriy Kolyukhin, and Hans Christian Tengesdal

scale (e.g., Thorpe 2007 ). However, the degree and amount of anisotropy is not well constrained and would require additional complications in the stochastic modeling. Therefore, we leave the theoretical investigation of anisotropy for future studies. However, anisotropic effects have been shown to be important in the context of long-range sound propagation and acoustic tomography ( Flatte and Colosi 2008 ). In particular, the horizontal correlation length of sound speed perturbations induced by

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Jerome A. Smith

came to light that the contribution of gravity acting on the “new modes” is quite small, comparable perhaps to the neglected effects of sound-speed variations or nonlinearity. It therefore seems advantageous to consider them as very slightly modified acoustic modes, which can be treated much more quickly, and for which other known effects can be included that may be more important in long-distance propagation (e.g., refraction, nonlinearity, scattering, and subbottom propagation or penetration

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Zhongxiang Zhao, Eric A. D’Asaro, and Jeffrey A. Nystuen

generation and absorption. Instead, we present empirical fits to our sound measurements ( appendix B ; Fig. 11 ) in the hope that other researchers may find the method useful to interpret ocean acoustic data. 5. Discussion These data show both the spectrum of underwater ambient sound at very high wind speeds and its distribution with depth. An understanding of the spectrum requires detailed modeling of wave breaking, bubbles, and acoustics, for example, Deane and Stokes (2010) , which is beyond the

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Rick Salmon

spurious effects whenever the acoustic deformation radius c / f is less than the domain size. Repeating the experiments shown in Figs. 4a–d for the case c / f = 2 π of acoustic deformation radius equal to the domain size, we find this difference to be negligible. However, when c / f is much less than the domain size, the Arakawa and splitting solutions differ significantly; for example, Fig. 4e shows the vorticity at t = 100 for a splitting-algorithm solution in which c / f = 2 π /10

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Shani Rousseau, Eric Kunze, Richard Dewey, Kevin Bartlett, and John Dower

with up to 10 4 individuals per cubic meter ( De Robertis 2002 ; De Robertis et al. 2003 ; Parsons et al. 1983 ; Mackie and Mills 1983 ; Beveridge 2007 ), one to two orders of magnitude higher than typical open-ocean densities ( Greenlaw 1979 ) and corresponding to 0.1% by volume. We rely on these extensive past measurements to assume that the migrating acoustic backscatter layer is dominated by Euphausia pacifica . This species dominates the diel migrating acoustic backscatter signal (−78 to

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Ruixiang Zhao, Xiao-Hua Zhu, and Jae-Hun Park

resolution (e.g., 9.9156 days for TOPEX/Poseidon, Jason-1 , Jason-2 , and Jason-3 ). Therefore, removing the aliasing effects on altimeter measurements is important for application of sea surface height products ( Carrère and Lyard 2003 ; Park and Watts 2006 ; Stammer et al. 2000 ). Acknowledgments This study was supported by the Project of State Key Laboratory of Satellite Ocean Environment Dynamics, Second Institute of Oceanography (SOEDZZ1701), the Scientific Research Fund of SIO (JT1604 and JG

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Brian D. Dushaw, Peter F. Worcester, Bruce D. Cornuelle, and Bruce M. Howe

September 1987. The accuracy of acoustical measurements ofrange-averaged heat content is comparable to estimates from CTD and XBT data. Transmissions at four-dayintervals allow the continuous observation of heat content and show that it varies on time scales of weeks orless. The magnitude of these variations is of the same order as that observed from XBT sections, which are onlyoccasionally available. Ocean-atmosphere heat exchange from bulk formulas accounts for only about half ofthe observed heat

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