Horizontal maximum velocity of internal solitary waves estimated from glider vertical motions east of Dongsha Atoll, South China Sea

Sen Jan1, Kai-Chieh Cathy Yang2, Ming-Huei Chang1, Yiing Jang Yang2, Joe Wang2, Steven Ramp3, D Benjamin Reeder4 and Dong Shan Ko5, (1)National Taiwan University, Institute of Oceanography, Taipei, Taiwan, (2)National Taiwan University, Taipei, Taiwan, (3)Soliton Ocean Services, Inc., Carmel Valley, CA, United States, (4)Naval Postgraduate School, Oceanography, Monterey, CA, United States, (5)Naval Research Laboratory, Stennis Space Center, MS, United States
Internal solitary waves (ISWs) are ubiquitous in the northern South China Sea and their anatomy is a contemporary interest of internal wave research. To examine ISWs and the enhancement of turbulence as westward propagating ISWs break over the shoaling topography east of Dongsha Atoll, field observations using multiple platforms have been conducted to the east of the Atoll from May to July 2019. Here we focus on the glider observed ISWs and the characteristics derived from the observations. A Kongsberg Seaglider was launched east of Dongsha (1017 m depth) on 19 May and was set to stay at the same location for a profiling survey until 24 May. In 9 of 33 dives, the glider were apparently heaved or depressed by a passing ISW. The vertical velocity induced by the ISW is deduced from the forced vertical motion of the glider, which varies between -0.31 and 0.46 m s-1. Accordingly, the maximum horizontal velocity of the first mode ISW is estimated from the vertical velocity using hydrographic profiles through the theoretical modal structure of the ISW, and further compared with shipboard acoustic Doppler current profiler (ADCP) and moored ADCP measured horizontal velocity. This presentation demonstrates results of the comparisons.