Significant internal waves and internal tides measured northeast of Taiwan

Author Posting. © The Author(s), 2013. This article is posted here by permission of Sears Foundation for Marine Research for personal use, not for redistribution. The definitive version was published in Journal of Marine Research 71 (2013): 47-81, doi:10.1357/002224013807343416.Internal gravity waves in an area northeast of Taiwan are characterized using data from multiple sensor types. The data set includes intermittent information collected from a ship and short time series from moorings. Modeled nonlinear waves are fitted to observed nonlinear waves to provide self-consistent estimates of multiple wave parameters. A nonlinear internal wave of over 50 m amplitude, observed in deep water, is examined in detail. This wave was moving northward from the southern Okinawa Trough toward the continental shelf, and presumably formed from internal tides propagating northward from the Ilan Ridge area. A possible scenario for the formation of this wave from the internal tide is compared to related behavior south of Taiwan. On the outer continental shelf, a few large internal waves with maximum displacement greater than one-quarter of the water depth were measured with moorings. Sensors aboard ship and satellite recorded waves in this area traveling in many directions. Two possible causes (not mutually exclusive) for the multiple wave directions are scattering of nonlinear internal waves arriving from the south, and variable local generation of nonlinear gravity waves by the strong tidal and internal tidal currents. Internal tides on the shelf are relatively strong, among the strongest measured, having about 10 times greater kinetic energy density than numerous low-energy sites, which is consistent with the strong barotropic tides of the area. The ratio of diurnal baroclinic to barotropic kinetic energy found in this area is unusually high.Funding for the use of RV OR1 was provided by the National Science Council of Taiwan. TFD was supported by the Office of Naval Research (ONR) Ocean Acoustics Program under grants N00014-05-1-0482 and N00014-11-1-0194. AEN was supported under ONR grant N00014- 08-1-0763, and GG under ONR grant N00014-07-01-0482. HCG and MJC were supported by ONR grants N00014-09-1-0392 and N00014-07-1-0650