Departmental Bulletin Paper 小笠原諸島周辺海域における海洋構造の季節変化
Seasonal variations of the hydrographic structure around the Ogasawara islands

藤原, 将平  ,  磯田, 豊  ,  妹尾, 浩太郎  ,  高木, 省吾

65 ( 1 )  , pp.1 - 15 , 2015-03-16 , 北海道大学大学院水産科学研究院
ISSN:1346-1842
NCID:AA11547977
Description
Using a two-layer model driven by the annual change in wind stress, Isobe and Imawaki (2002) suggested that the topographic effect of Izu-Ogasawara Ridge generates the baroclinic activity through the impinging process due to the barotropic response over the bottom slope, but there is no observed evidence for such process. To seek the indirect evidence of the impinging process in this study, seasonal variations of isopycnic vertical displacement over the ridge are investigated through analysis of monthly sea level at Chichijima and hydrographic data around the Ogasawara islands. Although annual signals of sea level and density field were largely masked by the westward propagating synoptic eddies with several-month time scale, we could detect annual cycle of isopycnic surfaces around the permanent pycnocline out of phase with that of sea surface mixed layer, i.e., it moves downward in summer (May to July) and upward in winter (November to January). Furthermore, this annual cycle was relatively amplified along the eastern hydrographic line at the intruding side of westward propagating barotropic waves. These results indirectly support the seasonal occurrence of impinging over the ridge.
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