Long-term observation of the Soya Warm Current using HF ocean radars: relationship between the Soya Warm Current variability and the sea level anomalies in the Soya/La Perouse Strait

• Published in: Journal of oceanography 2024-08, Vol.80 (4), p.239-249
• Main Authors: Ebuchi, Naoto, Fukamachi, Yasushi, Ohshima, Kay I., Mitsudera, Humio, Nishioka, Jun, Takatsuka, Toru, Ono, Kazuya, Ishikawa, Masao, Daibo, Takaharu, Shirasawa, Kunio, Wakatsuchi, Masaaki
• Format: Article
• Language: English
• Subjects: Altimetry; Annual variations; Anomalies; Current velocity; Earth and Environmental Science; Earth Sciences; Freshwater & Marine Ecology; Oceanography; Offshore; Original Article; Satellite altimetry; Sea level; Seasonal variation; Seasonal variations; Spacecraft recovery; Straits; Summer; Surface velocity; Tide gauges; Velocity
• ISSN: 0916-8370; 1573-868X
• DOI: 10.1007/s10872-024-00724-w

Three high-frequency (HF) ocean radars were installed at the Soya/La Perouse Strait to monitor the surface current fields of the Soya Warm Current (SWC), which flows through the strait from the Sea of Japan to the Sea of Okhotsk. These ocean radars were operated for 19 years, from August 2003 to March 2022. In this paper, seasonal to interannual variations in the SWC were investigated using surface current fields obtained by the HF ocean radars combined with coastal tide gauge records and sea level anomaly from satellite altimetry. The HF ocean radars clearly captured the seasonal and interannual variations in the SWC. The alongshore surface velocity of SWC showed a high correlation with the alongshore sea level difference (SLD) between the Sea of Japan and the Sea of Okhotsk if seasonal variations were included. However, anomalies of the SLD and SWC alongshore velocity exhibited a lower correlation, especially in summer. This suggests that different mechanisms may be involved in summer and winter. The alongshore SLD between Wakkanai and Abashiri, which has been utilized in previous studies as an indicator of SWC intensity, may not be appropriate for representing interannual variations in the SWC intensity in summer, when the SWC reaches the maximum current velocity. Instead, it was demonstrated that the offshore SLD anomaly estimated using satellite altimetry with the coastal tide gauge record at Wakkanai could be a better index for representing the interannual variations throughout the year.