Ocean Currents and Sea Surface Height (SSH) Variability in the Kuroshio Extension from a mooring system.

On the western side of the Shatsky Rise we investigate the variability of the Kuroshio Extension (KE) using a tall mooring and multiple pressure senor-equipped inverted echo sounder (PIES) from 2017 to 2019. The tall mooring measured currents using an upward-looking 75 kHz ADCP at 650 m, current meters at 940 m, 2060 m, and 4090 m depths, and a downward-looking 300 kHz ADCP near the bottom (5500 m). The PIESs measured the bottom pressure and round-trip acoustic travel time (τ) from the bottom to surface. In this study area there are many CTD profiles, and we were able to construct a high quality look-up table that are necessary when converting the travel time to vertical profiles of temperature and salinity. From τ dynamic height anomalies were calculated to estimate the geostrophic currents with which the current data from the mooring are decomposed into geostrophic and ageostrophic components. When the main axis of the KE is near the tall mooring, ageostrophic components intensify. From the pressure data we extracted barotropic (for variations in mass-loading) and from τ baroclinic (for density changes at constant mass) components of surface height anomalies (SSHA). The SSHA from the PIESs are then compared to those from altimeters. The baroclinic variability from the PIESs have high correlation with satellite SSHA. At the northern site, the meandering of the KE is the main cause of the baroclinic variability. At the southern site the effect of the meandering is much weaker.