2006 Volume 15 Issue 3 Pages 267-281
Spatial distributions of baroclinic flow and water mass in the “Transition Domain” (TD), defined between the Subarctic Front and Subarctic Boundary in the northern North Pacific, were investigated through analysis of long-term hydrographic data taken in 155°E, 165°E, 170°E, 175.5°E, and 180° meridians. Along the 170°E meridian, the Emperor Seamounts is located across the TD in a strict north to south direction. Although the TD could be clearly detected on both sides of the Emperor Seamounts, it frequently disappeared and had a remarkable watermass front, i.e., abrupt and meridional, changing from subtropical to subarctic water masses, int he location of the Emperor Seamounts. Furthermore, along the eastward transport of the TD, an abrupt zonal change from subarctic to subtropical water took place. In each year, the estimated eastward baroclinic flow around the TD suggested a shift to the north after passage through the trench of the Emperor Seamounts around 43°N (between Suiko Seamount and Nintoku Seamount), although small year-to-year changes were shown in its intensity and horizontal distribution. This shift in flow might explain the above zonal water mass change in the TD. It was also shown that the density of the “Central Mode Water”, formed at the sea surface mixed layer in winter, was gradually lighter from the west to the east.
