Seasonal variability of the Kuroshio Current at the PN Section in the East China Sea based on in-situ observation from 1
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Seasonal variability of the Kuroshio Current at the PN Section in the East China Sea based on in-situ observation from 1987 to 2010 WEI Yanzhou1, 2, PEI Yuhua3, 4*, ZHANG Rong-Hua1 1 Key Laboratory of Ocean Circulation and Wave, Institute of Oceanology, Chinese Academy of Sciences, Qingdao
266071, China 2 University of the Chinese Academy of Sciences, Beijing 100049, China 3 State Key Laboratory of Satellite Ocean Environment Dynamics, Second Institute of Oceanography, State Oceanic
Administration, Hangzhou 310012, China 4 College of Physical and Environmental Oceanography, Ocean University of China, Qingdao 266100, China
Received 14 August 2014; accepted 20 November 2014 ©The Chinese Society of Oceanography and Springer-Verlag Berlin Heidelberg 2015
Abstract
As the spatio-temporal variability of the Kuroshio is highly influenced by mesoscale eddies, representing its seasonal variability characteristics requires sufficiently long term observations to reduce the uncertainties. Geostrophic velocity data estimated from hydrographic observation from 1987 to 2010 and the shipboard ADCP velocity data from 1993 to 2008 at the PN Section in the central East China Sea are collected to view the seasonal variability objectively. From both types of observation, it is found that the seasonal climatology mean of the Kuroshio Current exhibits significant difference in three areas, which are located at the Kuroshio Current core and its two flanks in a shallow layer less than 300 m, with the weakest northeast current at the core in autumn, the strongest counter current on the right flank in spring, and the strongest northeast current on the left flank in autumn, respectively. The seasonal variance of the Kuroshio Current also exhibits significant difference on the offshore side of the Kuroshio, with larger variance in spring and summer while smaller variance in autumn and winter. For the current parallel to the PN Section, the ratio of the seasonal variability component to the intraseasonal variability component is relatively smaller than that for the current perpendicular to the PN Section. Further analyses indicate that the seasonal variability at the PN Section is tightly linked to the upstream and downstream current variability. Key words: Kuroshio Current, seasonal variability, East China Sea, significance test Citation: Wei Yanzhou, Pei Yuhua, Zhang Rong-Hua. 2015. Seasonal variability of the Kuroshio Current at the PN Section in the East China Sea based on in-situ observation from 1987 to 2010. Acta Oceanologica Sinica, 34(5): 12–21, doi: 10.1007/s13131-015-0662-3
1 Introduction The Kuroshio in the East China Sea (ECS) is part of the North Pacific subtropical gyre (Fig. 1), transporting huge amount of nutrients and heat poleward and having great impact on climate in surrounding areas (Nitani, 1972; Guan, 1988; Su et al., 1990). Therefore, the spatio-temporal variability of the Kuroshio Current on multiple scales is of wide interest to the oceanographic and climate communities. Take a bird’s eye view of sea surface heigh
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