| Research Abstract |
Mechanisms of the anomalous southward intrusion of the Oyashio and the subarctic circulations in the North Pacific have been studied with special reference to the possible prediction method for their occurrence. In the first year, the basic dynamics of the generation of the anomalous southward intrusion was studied. It has been demonstrated that the southward intrusions of the Oyashio and the subarctic circulation are due to the wind stress change by the southward development of the Aleutian Low (Sekine, 1990). The prediction of the southward intrusion of the Oyashio and subarctic circulation is show to be possible by the southward development of the Aleutian Low in winter and by the lack of the warm water detached from the Kuroshio Extension and eastward development of the Tsugaru Warm Current.
It is inferred that the wider cold sea surface temperature (SST) formed by the southward intrusion has a remarkable influences on the global atmospheric circulation. The relationship between the
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anomalous southward intrusion and the global change in atmospheric circulation was studied in the second year. As the southward development of the Aleutian Low is one process of the Pacific/North American (PNA) pattern, the anomalous southward intrusion of the Oyashio and subarctic circulation is shown to be a global phenomena that has a teleconnection with the ENSO phenomenon in equatorial area (Sekine and Suzuki, 1991). Since the PNA pattern has a tendency to occur in one year later than the onset of the warm water appearance off Ecuador, the prediction of the anomalous southward intrusion is possible by the evolution of the ENSO phenomenon. Because the southward development of the Aleutian Lowis independently by formed by the cold SST due to the southward intrusion, the positive feedback of the southward intrusion to the the southward development of the Aleutian Low. However, Sekine and Nakagawa (1992) and Sekine et al. (1992) showed that the sea ice area in the Okhotsk Sea is relatively small in winter with the anomalous southward intrusion, which suppresses winter cooling of the atmosphere. As the coupled global changes in atmosphere and ocean are important events, some future problems are left out to draw a firm conclusion on their total systems. Less
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