Generation of Nonlinear Internal Waves by the Transcritical Flow in the Kara Gates Strait

In this study, we investigate the generation of nonlinear internal waves (NLIWs) by transcritical flow in the Kara Gates Strait. The analysis of the NLIW generation mechanisms is carried out on the basis of in-situ measurements obtained during «Floating University-2023» expedition in July 2023, and data of Arc2kmTM tidal model. The values of the linear phase velocity of the first mode internal waves in July 2023 ranged from 0.3 to 0.7 m/s. Based on these estimates and model fields of tidal current velocity, the Froude number values in the strait were calculated and its temporal variability was determined. During the tidal cycle, the area of the strait occupied by transcritical and supercritical ( > 1) flow regimes can increase substantially.. In a number of areas of the strait, conditions favorable for the generation of NLIWs are observed twice during the 2 tidal period or 4 times a day. Analysis of synchronous measurements from on board a drifting vessel showed that the flow regime during an 8-hour period successively changed from supercritical to transcritical and then to subcritical values. The total number of NLIW trains and pronounced solitary oscillations, as well as their height and steepness, increased significantly during the period of weakening tidal currents at subcritical values of the Froude number, qualitatively corresponding to the theory of the formation and propagation of NLIWs in the transcritical regime.