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Nicolas Grisouard and Leif N. Thomas

fronts when viscous effects are taken into account. We also introduce a simplified linear analytical model, which highlights the role of viscous dissipation and of critical and near-critical reflections when exchanging energy with fronts. In section 4 , we present numerical simulations, which are linear in the sense that we cancel all explicit advective terms to test the analytical predictions. In section 5 , we discuss three effects that could potentially modify our conclusions, namely, the value

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Jonathan Gula, M. Jeroen Molemaker, and James C. McWilliams

model and also found that the error in hydrostatic balance remains small in most places. The degree to which nonhydrostatic effects will impact filamentogenesis at these scales is probably small but is currently unquantified. The filament examples presented here happen during late winter conditions for the Gulf Stream. Although similar types of filaments can be found at all times throughout the year, seasonal variations are usually significant for submesoscale fronts and filaments, especially in the

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Katherine McCaffrey, Baylor Fox-Kemper, and Gael Forget

for the quasigeostrophic flows. For all cases, passive tracers should behave as Obukhov and Corrsin predict when E ( k ) ∝ k −5/3 , or as the single eddy-turnover time-scale result of λ = −1 ( γ = 0) when E ( k ) ∝ k −3 . However, the wavenumber range where these spectral slopes should appear in quasigeostrophic flow is unclear as the effects of “surface” quasigeostrophy (SQG) and “interior” QG differ strongly in spectral slope and depth ( Tulloch and Smith 2006 ; Callies and Ferrari 2013

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Michael A. Spall

ice freezing and melting, shelf–basin exchange, the combined importance of salinity and temperature, and the range of possibly important forcing mechanisms, have made it difficult to develop a simple, conceptual model that describes the dominant features of the Arctic Ocean and relates them to the basic forcing parameters. Comprehensive models suggest that all of wind, heat, freshwater forcing, and the seasonal cycle are important; however, even these complicated models do not always produce

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R. M. Holmes and L. N. Thomas

1. Introduction Small-scale turbulent mixing of heat in the tropical Pacific is an important component of the sea surface temperature (SST) budget and contributes to changes in SST over a range of time scales. Variations in diapycnal turbulent transport play a role in the seasonal cycle of SST ( Moum et al. 2013 ) and the diurnal cycle in SST ( Bernie et al. 2005 ; Danabasoglu et al. 2006 ). Modulations in turbulence at time scales of weeks to months associated with intraseasonal Kelvin waves

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Vamsi K. Chalamalla and Sutanu Sarkar

away from the wind-driven boundary layer, both in mixed layers and in seasonal thermoclines. The turbulent dissipation rate was estimated to be , where N is the buoyancy frequency. Diapycnal diffusivity can also be estimated ( Osborn 1980 ) using K ρ = Γ ε / N 2 , where Γ is the mixing efficiency, often taken to be 0.2. Observational studies of internal tides (e.g., Alford et al. 2006 ; Martin and Rudnick 2007 ; Levine and Boyd 2006 ) often infer the turbulent dissipation rate and diapycnal

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Jörn Callies and Raffaele Ferrari

the transects that includes the Gulf Stream does not give qualitatively different results. We also disregard seasonal variations—the qualitative characteristics of the spectra are independent of season in this dataset. More recent data from the same transect, but collected with a different instrument, do show a seasonal cycle with more energetic small scales in the winter mixed layer. The results in this paper should therefore be regarded as representative of times with no deep mixed layer. We

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