Hydrographic sections across the Kuroshio extension at 165°E and 175°W

Abstract

Two meridional CTD/O 2 sections were occupied across the Kuroshio extension in the autumn of both 1983 and 1984 along the longitudes of 165°E and 175°W. The western section spanned the latitudes 29°N–44°N, east of the Shatsky Rise and west of the Emperor Seamount chain. The eastern section was east of the Hess Rise between 28° and 44°N latitudes. The baroclinic flow across 165°E was concentrated into two eastward jets approximately 100 km wide which could be identified with the eastward extensions of the Kuroshio and Oyashio (subarctic) fronts. The former had an eastward volume transport of 56 ± 2 Sv while the latter had an eastward transport of 22 ± 3 Sv relative to the ocean bottom. These two narrow zones of flow were embedded in a broad zone of weaker, baroclinic volume transport to the west. To the east of Emperor Seamounts, the meridional density gradients were substantially reduced. While the signatures of the Kuroshio and subarctic property fronts were still evident, the 175°W section was dominated by eddies with meridinal scales of approximately 200 km. In 1983 one of these eddies appeared to be a detached warm-core ring of Kuroshio water. Salinity variations in the oxygen minimum layer indicate a deep property front at 30°N at both longitudes which may extend westward toward Japan to at least 152°E.