Seasonal variability of characteristics of nonlinear internal waves in the Kuril-Kamchatka region by Sentinel 1 data

Abstract

The seasonal variability of the surface manifestations of nonlinear internal waves (NIW’s) in the Kuril-Kamchatka region from December 2018 to November 2019 was investigated based on the analysis of the Sentinel 1 satellite imagery archive. On 827 satellite images, 1876 manifestations of NIW’s were registered with a wavelength from 80 to 1900 m, containing from 2 to 18 waves in a packet. It was identified that the number of NIW’s registered in the water area varied significantly during the year. The minimum number of manifestations was recorded from January to March, and the maximum number of manifestations was observed from July to September. Areas of the frequent occurrence of NIW’s manifestations were identified: near the Kunashir Island, over the Vityaz ridge, near Cape Shipunsky and in Kamchatka Bay. Manifestations of NIW’s in these areas were recorded in all seasons of the year. These areas accounted for about 53% of all registered manifestations of NIW’s, and their area was about 20% of the study region area. The calculation of the tidal body force criterion for the main diurnal and semidiurnal tidal harmonics made it possible to identify potential generation sites of internal tidal waves. About 70% of NIW’s manifestations in August were detected in areas close to potential generation sites of diurnal internal tidal wave K1. This is explained by closeness of the generation and the disintegration sites of internal tidal waves under conditions of being beyond the critical latitude, where the tidal frequency coincides with the inertial one. Using the example of the area above the Vityaz ridge, the connection between the seasonal variability in the number of recorded manifestations and the annual variations in the tidal body force for harmonics K1, O1 and P1, mixed layer depth, the surface wind speed and the Brunt-Vaisala frequency was shown. This is consistent with the results of studies carried out in the adjacent regions of the Pacific Ocean. The existing archives of the Sentinel-1 radar image and the continuation of this satellite mission in the future will make it possible to estimate the long-term variability of NIW’s characteristic and to assess the impact of climate change on them.