Investigation of Tidal and Subtidal Variations in Sea Level Close to the Southeastern Coast of Sakhalin Island Using Two-Year Time Series

Abstract

The results of the study of tidal and subtidal variations in sea level in the area of the southeastern coast of the Sakhalin Island and a series of atmospheric pressure and wind speed from the open website “Weather Schedule” are presented. Using spectral analysis, astronomical tides were studied and diurnal M1, K1 and semi-diurnal M2, S2 tidal harmonics with high energy were detected. The maximum heights of tidal waves have been determined and the tidal regime in the studied water area is classified as mixed with a predominance of diurnal tides. It is shown that sea level rises due to the impact of winds on the sea surface are observed in the northerly direction of the winds, which is associated with storm surge in the coastal zone of Mordvinov Bay. The lowering of the sea level is observed with southerly winds and it is caused by the downsurge. The magnitude of the decrease in sea level for events that have a correlation between high wind speeds and the duration of influence to the winds of the western directions is maximal, and the wind speed has less influence on the magnitude of the decrease in level than its duration. Calculations of the level response to changes in atmospheric pressure using the Proudman equation and analysis of the results showed that these events can be attributed to the phenomenon of the “inverted barometer”. A comparison of theoretical profiles calculated from the time form of the Korteweg–de Vries equation with the registered profiles of sea level showed that they are well described by the profile of a solitary wave.