Given the essential impact of mixed-layer temperature (MLT) seasonality in Kuroshio–Oyashio Confluence Region (KOCR) on the variations of climate and marine economic species, the present study investigates causes of seasonal MLT anomaly (MLTA) in KOCR under bimodal states of Kuroshio Extension (KE). The results reveal that KE bimodality plays a modulation role in the seasonal variability of MLTA in KOCR. There is an opposite seasonal variation trend of MLTA under different KE states, and the MLTA amplitude in cold season (winter and spring) is larger than that in warm season (summer and autumn). Such behavior is directly induced by different distribution of climatological MLT and wind field in cold and warm seasons, as well as the opposite anomalous velocity of wind and ocean currents nearby KOCR associated with different KE states through changing sensible and latent heat flux, Ekman and geostrophic advection. The results suggest the dependency of short-term (seasonal) variability of KOCR-MLTA on the long-term (decadal) variations of KE background state.

鉴于黑潮-亲潮汇流区 (KOCR) 混合层温度 (MLT) 季节性对气候和海洋经济物种变化的重要影响，本研究调查了 KOCR 双峰状态下季节性 MLT 异常 (MLTA) 的成因黑潮扩展 (KE)。结果表明，KE 双峰性在 KOCR 中 MLTA 的季节性变化中起调节作用。不同KE状态下MLTA存在相反的季节变化趋势，冷季（冬春季）MLTA幅值大于暖季（夏秋季）。这种行为是由冷暖季节气候MLT和风场的不同分布直接引起的，以及通过改变感热和潜热通量、埃克曼和平流和地转平流，与不同的 KE 状态相关的 KOCR 附近风和洋流的相反异常速度。结果表明 KOCR-MLTA 的短期（季节性）变化依赖于 KE 背景状态的长期（年代际）变化。