Interannual variations of the Western Subarctic Gyre in the North Pacific
Tomowo Watanabe
National Research Institute of Far Seas Fisheries
Decadal-scale variations of the Western Subarctic Gyre in the North Pacific are analyzed by using the subsurface temperature in summer. The main data source is the data accumulated by salmon research group in the National Research Institute of Far Seas Fisheries for the period after 1964. The shift in the mid-1970's related to the climate shift in the North Pacific clearly appeared as cold anomalies in the Subarctic Boundary region and as warm anomalies in the Alaskan Stream region for the period after the mid-1970's. The pattern of the temperature anomalies indicates the strengthening and / or the southward shift of the gyre caused by the change of the wind system in the mid-1970's. The oscillation with 10-year period is detected in the temperature minimum layer that is formed around 100m depth in summer. The oscillation was amplified in the period from 1970 to 1990 and the layer was colder (warmer) in the periods 1970-75 (76-80) and 1981-85 (86-90). As the temperature minimum layer is the reminds of the wintertime deep and cold surface mixed layer, the variations found in the layer is influenced by the meteorological conditions of the previous winter. Wintertime atmospheric variations in the Northern Hemisphere are thought to be responsible for the oscillation of subsurface temperature.
