Abstract
In recent years, anomalous southward intrusions of the Oyashio havebeen observed frequently from winter to late spring. A barotropic model is usedto see the occurrence of the Oyashio intrusion, with special reference to a shorttime lag between the change in the wind stress in midwinter and the occurrenceof the Oyashio intrusion generally in spring of the same year. It is shown thatthe barotropic response of the ocean to the change in wind stress is fast, and itsrepresentative time scale is about 50 days at most. The southward shift of the Oyashio and the subarctic circulation are simulated quantitatively, when the imposedwind stress is changed from the mean wind stress prior to no Oyashio intrusion tothat prior to the Oyashio intrusion. It is suggested that the southward intrusionof the Oyashio is a phenomenon connected with the global change in atmosphericcirculation.
