THE SUBARCTIC FRONTAL ZONE OF THE PACIFIC OCEAN AT 180—130ºW IN SEPTEMBER—OCTOBER 1986

V. A. Petrova

Position and structure of the subarctic frontal zone are determined from CTD soundings made in September—October 1986. The frontal boundary between subarctic and subtropical waters is represented as an inclined plane crossing surface and subsurface layers in the area of the subarctic front and isopycnic surfaces 26.6—27.0σθ in the area of the northern subtropical front. Farther east the subarctic waters are considerably transformed in the upper 400-m layer, and subtropical waters are transformed in the upper 200-m layer. A contribution of temperature and salinity variations to the horizontal density gradient at the fronts of the subarctic frontal zone and to the vertical density gradient in waters with different vertical structure is determined. The research confirms that the salinity minimum at intermediate depths forms everywhere at the interface of subarctic and subtropical waters as a result of lateral isopycnic mixing and under the influence of fine-structure mechanisms of ocean waters.