Response of Spatial and Temporal Variations in the Kuroshio Current to Water Column Structure in the Western Part of the East Sea

Abstract

Using geographic sea surface current data, long-term changes in spatial and temporal variations in the Kuroshio Current 1993–2021 were analyzed, and the relationship between the Kuroshio Current and oceanic conditions, such as water column structure and intensity of East Korea Warm Current (EKWC) in the western part of the East Sea (WES), was investigated. Long-term changes in the Kuroshio Current intensity were positively correlated with the Pacific Decadal Oscillation and East Asian Winter Monsoon indices. When the Kuroshio Current was strong, its main axis passing around the Ryukyu Islands moved eastward, and the intensity of EKWC separated from the Kuroshio Current and flowed into the WES, indicating weakened conditions. When the intensity of the EKWC was weakened, its main axis moved away from the inshore area of the WES. As a result, the vertical distribution range of the cold and low saline water mass located in the bottom layer extended to shallower depths in the inshore area of the WES with increasing chlorophyll-a.

The Long-Term Dynamics of Walleye Pollock Stocks in Relation to Oceanographic Changes in the East Sea

“…For the Alaska Pollock inhabiting the Alaska region, the mortality rate within the first five months after hatching is 66-88% [19]. In Korean waters, the rate of warming in the upper layer, which serves as the primary habitat for larvae and eggs, is higher than that of the intermediate and deep layers where adult pollocks reside [47]. These changes in oceanic conditions in spawning grounds affect mortality during the early life stages [10,48,49].…”

“…Additionally, the weakened EAWM after the late 1980s and intensified northward warm current might have created unfavorable conditions for the walleye pollock in the late 1980s [17]. Furthermore, during periods of a weak Kuroshio Current combined with El Niño [61,62], the effect of Ekman transport on the Kuroshio Current flowing in the East China Sea was weakened, causing the main axis of the Kuroshio Current to migrate westward with decreased velocity [7,47,61,63]. Consequently, the Tsushima Warm Current, which flows into the East Sea and separates from the Kuroshio Current, was enhanced [7,47,61,63].…”

“…Furthermore, during periods of a weak Kuroshio Current combined with El Niño [61,62], the effect of Ekman transport on the Kuroshio Current flowing in the East China Sea was weakened, causing the main axis of the Kuroshio Current to migrate westward with decreased velocity [7,47,61,63]. Consequently, the Tsushima Warm Current, which flows into the East Sea and separates from the Kuroshio Current, was enhanced [7,47,61,63]. As a result, oceanic conditions in the East Sea indicated warmer than normal conditions.…”

Spatial Dynamics of Demersal Fish Assemblages off the Korean Coast in the East Sea

“…Marine environments, such as water temperature and salinity in the East Sea off the Korean coast, exhibit high variability depending on the latitudinal path of oceanic currents [ 12 ]. Notably, latitudinal patterns of water temperature are evident in the surface layers influenced by two major oceanic currents: the East Korea Warm Current (EKWC) flowing into the East Sea via the Korean Strait, and the North Korea Cold Current (NKCC) branched from the Liman Cold Current (LCC) flowing southward along the eastern coast of the Korean Peninsula from the north [ 12 , 13 , 14 ]. These interactions divide marine ecosystems in the southwestern part of the East Sea into cooler northern and warmer southern sections [ 15 ].…”

Integrated Ecosystem Assessments for Fisheries Management in the Yellow Sea, the East China Sea, and the East/Japan Sea

“…Lee et al (2022a) [1] investigate the water column dynamics of the East Korea Warm Current in the western East Sea responding to spatiotemporal variability in the Kuroshio Current. This article expands our understanding of the potential mechanisms for climate change and its effects on the oceanic environmental conditions and subsequent response of fishery resources in the western East Sea.…”