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Internal wave-driven mixing is an important factor in the balance of heat and salt fluxes in the polar regions of the ocean. The breaking internal waves at the edge of the ice cover can essentially enhance the mixing and melting of ice in the Arctic Ocean and Antarctica. The internal solitary waves (ISWs) are generated by various sources, including tidal currents over the bottom topography, the interaction of ice keels with tides, varying in time wind, vortices, and lee waves. In the study, a numerical investigation of the transformation of ISW propagating from open water in the stratified sea under the edge of the ice cover is carried out to compare the depression ISW transformation and loss of energy on smooth ice surfaces, including those on the ice shelf and glacier outlets, with the processes beneath the ridged underside of the ice. They were carried out using a nonhydrostatic model which is based on the Reynolds averaged Navier-Stokes equations in the Boussinesq approximation for a continuously stratified fluid. The Smagorinsky turbulence model extended for stratified fluid was used to explicitly describe the small-scale turbulent mixing. Two series of numerical experiments were carried out in an idealized 2D setup. The first series aimed to study processes of the ISW-depression transformation under ice cover of constant submerged ice thickness. A loss of energy was estimated based on the budget of depth-integrated pseudoenergy before and after the wave transformation. The transformation of depression ISW is controlled by the blocking parameter β. For large positive and large negative values of parameter β which is the ratio of the height of the minimum depth of the upper layer under the ice cover to the incident wave amplitude. The energy loss was relatively small for large positive and large negative values of β. The maximal value of energy loss was about 38 % and it is reached at β ≈ 0 for ISW. In the second series of experiments, a number of keels were located underside of the ice layer of constant thickness. The ISW transformation under ridged ice also depends on the blocking parameter β. For large keels (β<0), more than 40 % is lost on the first keel, while for relatively small keels (β>0.3), the losses on the first keel are less than 6 %. Energy losses due to all keels depend on the distance between them which is characterized by the parameter μ which is the ratio keel depth to the distance between keels. If the tidal flow around the large keels is the source of internal waves, then under conditions of strongly ridged ice the waves excited by the tidal flow are dispersed in the vicinity of their formation. [ABSTRACT FROM AUTHOR]

Internal solitary waves (ISW) emerge in the ocean and seas in different forms and break on the shelf zones in a variety of ways. Their breaking on slopes can produce intensive mixing that produces such process as biological productivity and sediment transport. Mechanisms of ISW of depression interaction with the slopes related to breaking and changing polarity as they shoal. We assume that parameters that described the process of interaction of ISW in a two-layer fluid with the idealised shelf-slope are: the non-dimensional wave amplitude α (wave amplitude normalized on the upper layer thickness), the ratio of the height of the bottom layer on the shelf to the incident wave amplitude β and angle γ. Based on three-dimensional αβγ classification diagram with four types of interaction with the slopes it was discussed: (1) ISW propagates over slope without changing polarity and wave breaking; (2) ISW changes polarity over slope without breaking; (3) ISW breaks over slope without changing polarity; (4) ISW both breaks and change polarity over the slope. Relations between the parameters α,β,γ for each regime were obtained using the empirical condition for wave breaking and weakly nonlinear theory for the criterion of changing the polarity of the wave. In the present paper the α,β,γ diagram was validated for idealised real scale topography configurations. Results of the numerical experiments that were carried out in the present paper and results of field and laboratory experiments from other papers are in good agreement with proposed classification and estimations. Based on 85 numerical experiments ISWs energy loss during interaction with slope topography with 0.5° < γ < 90° was estimated. Hot spots zones of high levels of energy loss were shown for idealized configuration that mimics continental shelf at Lufeng Region SCS. [ABSTRACT FROM AUTHOR]

Interaction of the first mode solitary wave with bottom step in three-layer flow is studiednumerically. Two modes of the internal waves exist in the three layer flow. Interaction of thefirst mode internal solitary wave with an obstacle is one of the known mechanisms ofgeneration of the second-mode internal solitary waves. The second mode internal solitarywaves appear as in the reflected wave field as well as in the transmitted wave field. In the caseof thick intermediate layer secondary solitary waves of the second mode take convexform. Dependence of the generated second-mode solitary waves in transmitted andreflected wave of amplitude on the incident wave amplitude are studied. Energytransfer from the first mode into second modes during transformation is also studied [ABSTRACT FROM AUTHOR]