Fig. 2 Lag correlation between deviation from monthly mean southern most latitude of the Oyashio and deviation from monthly mean sea ice area in Okhotsk Sea. Positive (negative) lag means that the sea ice area of the Okhotsk Sea is delayed (preceded) for the southernmost latitude of the Oyashio. Significant correlation of 95% confidence is shown by dot lines.
RESULTS
Lag correlation between the deviation from monthly mean southernmost latitude of the Oyashio (Fig. 1a) and the deviation from monthly mean of the sea ice area of the Okhotsk Sea (Fig. 1b) is shown in Fig. 2. All the lag coefficients of the correlation are positive and significant positive correlation are detected, if five to six months lag are applied for the southernmost latitude of the Oyashio. Because the southernmost latitude of the Oyashio (Fig. 1a) has a lag of three〜four months to the change in wind stress and actual southernmost latitude (Sekine, 1999), the significant positive correlation with a lag of two months is resulted between sea ice area of the Okhotsk Sea and the actual southernmost latitude of the Oyashio.
In order to see content of the positive correlation between sea ice area of the Okhotsk Sea and southernmost latitude of the Oyashio (Fig. 2), the sea ice areas in the Okhotsk Sea in winter with the anomalous southward shift of the Oyashio and subarctic circulation, namely 1974, 81, 84 and 86, and those in other winters over 1971-1988 are compared in Fig. 3. The sea ice area in the anomalous southward intrusion of the Oyashio is smaller than those in other winter. The smaller sea ice area in the Okhotsk Sea is associated with a warmer temperature around the Okhotsk Sea more than 3 degree in winter with the anomalous southward shift of the Oyashio (Sekine et al., 1996). This warm temperature is suggested to induce the small sea ice area in the Okhotsk Sea.
