Generation of periodic intrusions at Suruga Bay when the Kuroshio follows a large meandering path

• The first time to measuring the multi-layer current at the Suruga Bay when the Kuroshio takes the typical large meandering path.
• Detect the current variation of the Near-20-days period at the Suruga Bay.
• The sea level perturbation which has Near-20-days period propagates from the Hachijo-Island to the Suruga Bay.
• The Near-20-days period variations of the current and of the sea level are caused by passing of the Kuroshio frontal waves.

We measured the vertical profiles of currents at the eastern mouth of the Suruga Bay using a moored acoustic Doppler current profiler (ADCP). Currents vertical profiles were found to be mostly barotropic in structure when intrusions occurred at the eastern mouth of the bay. Warm-water intrusions at the Suruga Bay and sea level elevations at the bay and at islands on the Izu Ridge located off the bay have the same period of 26 days. The temporal variation in the sea levels occurs in response to Kuroshio frontal waves, and the two phases are consistent. The sea level rise propagates from Hachijo Island to the Suruga Bay via Miyake Island and Kozu Island, i.e., from off the Suruga Bay to in or near the bay. The perturbation of the sea level along the Izu Ridge occurs as waves with a period of 26 days, a wavelength of 500 km, and a phase speed of 23 cm/sec. The propagated waves and those of the Kuroshio frontal waves have the same features. This means that the periodic inflows at the eastern mouth of the Suruga Bay are caused by the passage of Kuroshio frontal waves off the bay.