SHORT-TERM VARIABILITY OF CURRENTS AND SEA SURFACE HEIGHT IN THE URAL RIVER PLUME, THE CASPIAN SEA

Abstract

This article repots the results of high temporal resolution in-situ measurements of coastal currents and sea level in the Kazakhstan sector of the Northern Caspian. Current velocity data were collected as 1 min averages for 72 hours at 3 moored automatic buoy stations spaced approximately 10 km apart, while those of bottom pressure (i. e., sea surface level) were obtained at one of the stations. The measurements were accompanied by CTD profiling at 18 stations. Wind speed and direction were simultaneously recorded using a portable weather station, with a 1 min temporal resolution. Energetic variability in currents and sea level was detected, manifested as oscillations on time scales centered at 11 and 21 hours. Currents at all stations showed a high simultaneous correlation with each other but no significant correlation with wind stress. Sea level variability was moderately correlated with current velocity, with the maximum correlation observed at a time shift of approximately 2.5 hours. The possible physical origins of the recorded oscillations are discussed, such as the intrinsic oscillations of the river plume due to the internal imbalance of the plume’s momentum and mass budgets, and also coastal trapped waves.