Short‐period fluctuations in meander of the Kuroshio's path off Cape Shiono Misaki

Abstract

Direct current measurements in the strong stream layer of the Kuroshio were carried out to investigate short‐period fluctuations of the small‐scale meander of the Kuroshio at two mooring stations off Cape Shiono Misaki in 1985–1986. The Kuroshio had a stable nonlarge meander path and flowed eastward parallel to the mooring stations during a large part of the observations, which were appropriate conditions for temporal analysis. Temperature and velocity variations reveal the existence of dominant periodic fluctuations in the small‐scale meander of the Kuroshio's path and its frontal disturbances. A fluctuation with a period of 17–19 days and 400‐km wavelength is found in association with small‐scale meander of the Kuroshio's path. Periodic fluctuations of 5–8 days and 10–12 days are also recognized and have 100‐km and 200‐km wavelength, respectively. Satellite imagery shows that the two periodic fluctuations are dominant in frontal regions as plumes from the north wall of the Kuroshio. The fluctuations with the three periodic bands propagating downstream at about 20 cm s−1 and transitions of wavelike disturbances of the Kuroshio front observed by satellite suggest that all of the propagations are subject to the barotropic component of the eastward velocity. The temporal and spatial characteristics of the Kuroshio meander show good correspondence with other observations in upstream regions of the Kuroshio. The phase speed of wavelike perturbations well recognized in the Gulf Stream region is approximately twice as large as that of Kuroshio perturbations. The difference seems to be caused by differences of water depth beneath the two streams.