Position variability of the Kuroshio Extension sea surface temperature front
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Position variability of the Kuroshio Extension sea surface temperature front WANG Yanxin1, YANG Xiaoyi1*, HU Jianyu1 1 State Key Laboratory of Marine Environmental Science, College of Ocean and Earth Sciences, Xiamen University,
Xiamen 361102, China Received 11 January 2016; accepted 3 March 2016 ©The Chinese Society of Oceanography and Springer-Verlag Berlin Heidelberg 2016
Abstract
High spatial resolution sea surface temperature (SST) data from 1993 to 2013 are used to detect the position of the Kuroshio Extension sea surface temperature front (KEF) from 141°E to 158°E, and the seasonal, monthly and interannual-to-decadal variations of the KEF position are investigated. The latitudinal position of the KEF varies with longitudes: the westernmost part of the KEF from 141°E to 144°E is relatively stable, whereas the easternmost part from 153°E to 158°E exhibits the largest amplitude of its north-south displacement. In the light of the magnitudes of the standard deviations at longitudes, then the KEF is divided into three sections: western part of the KEF (KEFw, 141°–144°E), central part of the KEF (KEFc, 144°–153°E) and eastern part of the KEF (KEFe, 153°–158°E). Further analysis reveals that the KEFw position is dominated by the decadal variability, while the KEFc and KEFe positions change significantly both on interannual and decadal time scales. In addition, the KEFw position is well correlated with the KEF path length. The possible mode leading to the decadal oscillation of the KEFw is further discussed. The KEFw position exhibits significant connections with the Pacific decadal oscillation (PDO) index and the north Pacific gyre oscillation (NPGO) index with a time lag of 40 and 33 months, respectively. Key words: Kuroshio Extension, Kuroshio Extension front, sea surface temperature Citation: Wang Yanxin, Yang Xiaoyi, Hu Jianyu. 2016. Position variability of the Kuroshio Extension sea surface temperature front. Acta Oceanologica Sinica, 35(7): 30–35, doi: 10.1007/s13131-016-0909-7
1 Introduction The Kuroshio is the western boundary current in the North Pacific Ocean. The warm, northward-flowing water of the Kuroshio seperates from the coast of Japan (35°N, 140°E) to flow eastward in the North Pacific Ocean. In the region 140°–180°E, this eastward-flowing current is called the Kuroshio Extension (KE). Being an extension of the western boundary current, the KE system has large-amplitude meanders and energetic pinched-off eddies (Mizuno and White, 1983; Qiu and Chen, 2005; Kelly et al., 2010). The KE system has an evident decadal modulation between a stable and an unstable state (Qiu and Chen, 2005; Taguchi et al., 2007). In its stable state, the eastward KE jet is strong; the position moves northward; the southern recirculation gyre strengthens; the eddy kinetic energy decreases accordingly and vice versa (Qiu and Chen, 2005). The transition between the two dynamic states of the KE system is induced by wind-stress curl anomalies in the eastern North Pacific Ocean (Seager et al., 2001; Qiu, 2003; Sasaki et al.,
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