[1] Numerical experiments are performed using the MITgcm to investigate the interaction of a mode-one internal tide with barotropic and baroclinic mode-one mesoscale eddies. Results show that after a mode-one internal tide passes through a barotropic eddy, spatial hot and cold spots of energy flux are produced in beam-like patterns. The magnitude of the energy flux in the hot spots can exceed twice the incident flux while in the cold spots can reach nearly zero. Passing a mode-one internal tide through a mode-one baroclinic eddy results in the scattering of energy from the incident mode-one to modes two and higher. The higher mode waves are produced in beam-like patterns. For the parameter regime explored here, we find conversion efficiencies that reach 13% for eddies of diameter 120 km. The Rossby numbers for our experiments are order one, corresponding to energetic mesoscale eddies that are typically found in western boundary current extensions and in the southern ocean. These eddies have length scales comparable to those of low-mode internal tides, and we expect that interaction between the two will be easily formed in locations where these phenomena coexist.Citation: Dunphy, M., and K. G. Lamb (2014), Focusing and vertical mode scattering of the first mode internal tide by mesoscale eddy interaction,

ABsTrACT. A tidal model of the Canadian Arctic Archipelago was used to map the strength of the tidal currents, tidal mixing (h/U 3 ), and the vertical excursion associated with the tidal currents that drive water upslope and downslope. The hot spots in these quantities correspond to the location of many of the small polynyas in the archipelago, supporting the idea that the tidal currents make an important contribution to the dynamics of many of these recurring polynyas. The potential link with tidal mixing means that these locations may have enhanced plankton production in the summer.Key words: Canadian Arctic Archipelago, polynyas, tidal currents, tidal mixing, tidal mixing fronts résuMé. un modèle des marées de l'archipel Arctique canadien a servi à mapper la force des courants de marée, le mélange de marée (h/U 3 ) et l'excursion verticale associés aux courants de marée qui poussent l'eau en ascendant et en descendant. les points chauds de ces quantités correspondent à l'emplacement d'un grand nombre des petites polynies de l'archipel, ce qui vient appuyer l'idée selon laquelle les courants de marée jouent un rôle important dans la dynamique d'un grand nombre de ces polynies récurrentes. le lien susceptible d'exister avec le mélange de marée implique que la production de plancton à ces emplacements pourrait être rehaussée à l'été.Mots clés : archipel Arctique canadien, polynies, courants de marée, mélange de marée, fronts de mélange de marée Traduit pour la revue Arctic par nicole Giguère.

Abstract. Internal solitary waves are widely observed in both the oceans and large lakes. They can be described by a variety of mathematical theories, covering the full spectrum from first order asymptotic theory (i.e. Korteweg-de Vries, or KdV, theory), through higher order extensions of weakly nonlinear-weakly nonhydrostatic theory, to fully nonlinear-weakly nonhydrostatic theories and finally exact theory based on the Dubreil-Jacotin-Long (DJL) equation that is formally equivalent to the full set of Euler equations. We discuss how spectral and pseudospectral methods allow for the computation of novel phenomena in both approximate and exact theories. In particular we construct markedly different density profiles for which the coefficients in the KdV theory are very nearly identical. These two density profiles yield qualitatively different behaviour for both exact, or fully nonlinear, waves computed using the DJL equation and in dynamic simulations of the time dependent Euler equations. For exact, DJL, theory we compute exact solitary waves with two-scales, or so-called double-humped waves.

Understanding and predicting how internal tides distort and lose coherence as they propagate through the ocean has been identified as a key issue for interpreting data from the upcoming wide-swath altimeter mission Surface Water and Ocean Topography (SWOT). This study addresses the issue through the analysis of numerical experiments where a low-mode internal tide propagates through a quasigeostrophic turbulent jet. Equations of motion linearized around the slower turbulent field are projected onto vertical modes and assumed to describe the dynamics of the low-mode internal tide propagation. Diagnostics of the terms responsible for the interaction between the wave and the slow circulation are computed from the numerical outputs. The large-scale change of stratification, on top of eddies and jet meanders, contributes significantly to these interaction terms, which is shown to be consistent with an independent scaling analysis. The sensitivity of interaction terms to a degradation of the slow field spatial and temporal resolution indicates that present-day observing systems (Argo network, altimetry) may lack the spatial resolution necessary to correctly predict internal tide evolution. The upcoming SWOT satellite mission may improve upon this situation. The number of vertical modes required to properly estimate interaction terms is discussed. These results advocate development of a simplified model based on solving a modest number of the linearized equations subject to a prescribed mesoscale field and internal tide sources.