Transformation of internal solitary waves at the "deep" and "shallow" shelf: satellite observations and laboratory experiment

Abstract

Abstract. An interaction of internal solitary waves with the shelf edge in the time periods related to the presence of a pronounced seasonal pycnocline in the Red Sea and in the Alboran Sea is analysed via satellite photos and SAR images. Laboratory data on transformation of a solitary wave of depression while passing along the transverse bottom step were obtained in a tank with a two-layer stratified fluid. The certain difference between two characteristic types of hydrophysical phenomena was revealed both in the field observations and in experiments. The hydrological conditions for these two processes were named the "deep" and the "shallow" shelf respectively. The first one provides the generation of the secondary periodic short internal waves -"runaway" edge waves -due to change in the polarity of a part of a soliton approaching the shelf normally. Another one causes a periodic shear flow in the upper quasi-homogeneous water layer with the period of incident solitary wave. The strength of the revealed mechanisms depends on the thickness of the water layer between the pycnocline and the shelf bottom as well as on the amplitude of the incident solitary wave.

Internal Solitary Waves Observed on the Continental Shelf in the Northern South China Sea From Acoustic Backscatter Data

“…The evolution of an ISW with an asymmetric waveform on a continental shelf mainly goes through four stages (Vlasenko and Hutter, 2002;Chang et al, 2021): (1) the frontal edge becomes more gently sloping while the rear edge becomes steeper; (2) overturning of the rear edge leads to heavy bottom fluid over light fluid; (3) the heavier fluid from the rear edge plunges into the wave core; and (4) heavier fluid in the wave core forms an enclosed isopycnal region. Strong water motion by ISWs can enhance bottom-boundary turbulence, water exchange in coastal areas, and surface phytoplankton primary productivity (van Haren et al, 2012;Shishkina et al, 2013;Alford et al, 2015;Masunaga et al, 2017;Jia et al, 2019). However, the spatiotemporal propagation and dissipation of a specific ISW in coastal areas are seldom reported.…”