Abstract

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.

Highlights

  • 20 One of the mechanisms of generation of the internal solitary waves (ISWs) in the seas and oceans is the tidal flows over ridges and steep topography, where they transform quickly into internal solitary waves during their propagation

  • 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 10 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

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Summary

Introduction

20 One of the mechanisms of generation of the internal solitary waves (ISWs) in the seas and oceans is the tidal flows over ridges and steep topography, where they transform quickly into internal solitary waves during their propagation. ISWs in SCS are generated by the interaction of internal tides and the system of two quasi-parallel ridges in the Luzon Strait (Alford (2015)) Such waves could propagate at vast distances toward Dongsha Atoll mainly in the form of mode-1 internal solitary waves where they shoal and dissipate at the shallow continental shelf (Liu (1998)). A simple three-dimensional αβγ classification diagram was proposed by (Terletska (2020)) to distinguish different regimes of transformation of ISW over the shelf-slope topography. The objectives are to: (1) compare αβγ classification with the results of numerical modelling, laboratory studies , and field observations, (2) find high energy dissipation zones of ISWs passed over the shelf-slope topography based on regimes classifi cation that includes such parameters as wave amplitude, stratification and slope, (3) for αβγ classification carry out numerical modeling for idealized configuration that mimics continental shelf at Lufeng Region SCS, (4) determine energy loss of the transformation of ISWs with the shelf-slope topography.

Regimes of ISW transformation over slope-shelf topography
Data and methods
Estimate of energy loss in internal waves breaking on slopes
Findings
Conclusions
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