Synoptic to Subseasonal Variability of Currents in the Southern Japan/East Sea

Abstract Some aspects of synoptic to subseasonal variability of currents in the southern Japan/East Sea (JES) were investigated using high-resolution current measurements and reanalysis model products. Current measurements were made at multiple moorings containing acoustic Doppler current profilers (ADCPs) deployed during MJES (Mixing in the Japan/East Sea, 2021–2022) and LINKS (Linkages of Asian Marginal Seas, 1999–2000) programs. MJES measurements were collected over the southern slope of the Ulleung Basin (SSUB) and near the southeastern coast of Korea, and LINKS measurements were collected within the Korea-Tsushima Strait (KTS). Both LINKS and MJES observations revealed synoptic (2–7 days) to subseasonal (7–30 days) velocity fluctuations. Specifically, velocity fluctuations in the East Korea Warm Current on the southeastern Korean shelf from March to June 2022 reached magnitudes of 0.3 m s⁻ 1 , with broad periods ranging from 10 to 15 days. Local winds and currents were highly correlated here with a coherence of 0.95 at 12–13-day periods and a 2.7-day lag. Similar velocity fluctuations were observed at moored ADCPs on the SSUB and the northwestern corner of the KTS, but without any significant correlations between winds and currents. However, atmospheric surface-pressure distributions over the JES displayed 10–15 day oscillating along-basin pressure gradients of magnitudes $$\sim$$ 10 –5 mb m −1 . Our analysis suggests that wind and atmospheric pressure-gradient forcing can be important forcing mechanisms for generating the observed velocity fluctuations in the southern JES.