Fine-Scale Measurements of Hydrophysical and Bio-Geo-Optical Properties by the Autonomous Moored Profiling Probe Winchi in the Waters of the Coastal Zone of the Northwestern Sea of Japan

In May–June 2024, an automatic mobile tethered Winchi profiler equipped with a YSI EXO2 Multiparameter Sonde was used to conduct fine-scale measurements of thermohaline stratification and bio-geo-optical parameters in Vityaz Bay (Peter the Great Bay, the Sea of Japan) for the first time. The data quality was improved by correcting the depth profiles of sea water temperature and absolute salinity to account for the response time of the temperature sensor, resulting in a reduction of the root-mean-square-error (RMSE) relative to reference profiles by factors of 5 and 6, respectively (final RMSE = 0.13◦C and 0.1 g/kg). The analysis revealed the presence of quasi-inertial (~18 hours) and diurnal (~24 hours) oscillations, as well as significant shifts in near-surface layer properties, through analysis of collocated thermohaline and bio-geo-optical data.