Variability of the Thermohaline Structure at the Continental Slope Off the Russian Coast, the Northwestern Japan Sea

Abstract

The study is based on unique data from the autonomous Aqualog profiler installed in the northwestern Japan Sea at the continental slope off the southeastern Primorye coast from April 18 through October 14, 2015. Data set for the 64–300 m depths, with the depth step of 1 m and time step of 6 hours, and the time series averaged for the 320–420 m depths, with the time step of 6 days, are used. Variability in the upper and lower profiled layers is found to be of different nature. Above 100–150 m short-lived (2–4 days) temperature and salinity anomalies are mostly of the same sign. Based on our earlier analysis of satellite information it is possible to link these anomalies with water intrusions of different origins. Conversely, these anomalies are usually of the opposite signs and are longer-lived (up to 10–15 days) in the lower layer which can be explained by vertical displacements of isopycnals, probably due to passing mesoscale and submesoscale disturbances. Based on wavelet transform it is found that the longest-period fluctuations (with the periods of 80–110 days) were the most intense in the entire profiled layer throughout the entire record. Isopycnal displacements with the periods of 80–110 days were also found, being in-phase with the temperature fluctuations. The wavelet transform also revealed that variability strengthened in the upper layer and weakened in the lower layer from mid-August onwards.