Interannual and Decadal Sea-Level Variations along the Japanese Coast |
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Authors: | Tomoharu Senjyu Masaji Matsuyama Naho Matsubara |
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Affiliation: | (1) Department of Fishery Science and Technology, National Fisheries University, 2-7-1, Nagata-honmachi, Shimonoseki, Yamaguchi, 759-6595, Japan;(2) Department of Ocean Sciences, Tokyo University of Fisheries, Konan 4-5-7, Minato-ku, Tokyo, 108-8477, Japan |
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Abstract: | Interannual (an annual to a decadal) and decadal sea-level variations along the Japanese coast have been investigated on the basis of monthly mean sea level during the period from 1951 to 1995. For the interannual variation, the Japanese coast is divided into six regions according to a regional similarity of sea level by using the cluster analysis, which is close to Tsumura's (1963) classification. The first mode of the Empirical Orthogonal Function (EOF) of the Interannual variation is the simultaneous rising and falling of the sea level along the Japanese coast. The first mode shows the largest variation in winter and has a negative correlation with the wintertime monsoon index; this suggests that the first mode is associated with a steric height change depending on the wintertime cooling intensity. The EOF second mode represents the Kuroshio large meander because strong negative eigenvectors are seen on the southeast coast of Japan and the time coefficient shows a high correlation with the Kushimoto-Uragami sea-level difference. For the decadal sea-level variation, the EOF first mode is a bi-decadal variation exhibiting simultaneous rising and falling of the sea level for the entire Japanese coast. The time coefficient of the first mode shows the first minimum in 1965, reaches a maximum in 1975, and decreases to the second minimum in 1984. The decrease from the mid-1970s and the increase from the mid-1980s to early 1990s correspond to the climatic regime shifts occurring in the same periods. |
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Keywords: | Interannual sea-level variation decadal-scale sea-level variation steric height change bi-decadal variation climate regime shift winter monsoon Kuroshio flow path regional similarity |
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