The lateral extent and characteristics of the North Pacific Central environment at 35°N

Abstract

The study concerns the physical, chemical, and biological characteristics, lateral extent, and heterogeneity of the North Pacific Central environment at latitude 35°N, in comparison with the environment at a long term study site at 28°N, 155°W. THe primary sta were collected in spring 1976, along a section from California to Japan. In July 1977, a segment of this section was repeated. Principal component analysis reduced the physical and chemical data from the 1976 section to four axes along which five environments were identified: the California Current, the Eastern North Central Pacific (ENCP), the Western North Central Pacific (WNCP), cold core stations (presumably meanders or rings from the Kuroshio extension), and the Kuroshio Current. The biological characteristics of these environments were assessed by means of a chlorophyll index, derived from a second principal component analysis. The ENCP was similar environmentally and biologically to the study site at 28°N, 155°W and was significantly more oligotrophic than the other environments. The chlorophyll index within the ENCP showed marked temporal and spatial stability, greater than in the WNCP. This stability may be related to the reduced hydrographic variability that physical oceanographers have observed in the eastern, mid-latitude portions of northern oceans.