620 EIGHTH PACIFIC SCIENCE CONGRESS 



bottom configuration of this area is suitable for an upwelling. Dr. 

 Uda and Dr. Koenuma explained this phenomenon as follows: When 

 the North Pacific High Salinity Water (Kuroshio Water) weakened 

 and the strength of the Subarctic intermediate water (Oyashio Water) 

 increased, this cold water mass appeared. He pointed out that prior 

 to the appearance of the cold water mass in 1934, cold water off the 

 coast of Sanriku prevailed so intensively that the northeastern part 

 of Japan had suffered a very cold summer in 1934-35. It may be ex- 

 plained that the weakening on the Kuroshio in recent years has caused 

 the appearance of a cold water mass in winter. 



Before the appearance of the cold water mass in 1934, the famous 

 Muroto typhoon had passed the central part of Japan, and in recent 

 years the cold water mass appeared after a strong typhoon passed near 

 this area. The effect of typhoon may be one of the causes of the up- 

 welling of cold water mass. 



Summarizing the above observations, the strengthening and weaken- 

 ing of the Kuroshio and Oyashio is the major cause of the appearance 

 of the cold water mass and the bottom configuration and typhoons have 

 much effect on it. 



2) A Violent Variation of Oceanographic Condition 



OFF THE BOSO PENINSULA 



It is well known by fishermen that ocean currents change their 

 course and other oceanographic conditions vary in a very short time. 

 But the oceanogiaphic observation is seldom carried out in so short an 

 interval that there are few examples for these variations in the record 

 of observations. 



In this paragraph Ave intend to describe an example in Avhich sev- 

 eral observations were carried out in a short interval in the same area, 

 and a large variation of oceanographic condition was observed. But in 

 this example, too, the shortest interval of observation was 10 days, and 

 from the variation of observed water temperature, etc., this is not suf- 

 ficient to make clear the detailed variation which was taking place in 

 the ocean. 



Figure 6 shows the sectional distribution of water temperature ob- 

 served by the Hydrographic Office from March to May, 1944, off the 

 Boso Peninsula. These five observations were carried out on an almost 

 similar line (Fig. 7). As in this area the Kuroshio deflects eastwards 

 departing from the Japan Islands and the Oyashio reaches to the north 

 of the Kuroshio, the oceanographic condition in this area is very varia- 

 ble. 



Between 3 and 25 March, the water temperature lowered to about 

 3-4°C in the whole region, and on 11 April there appeared a minimum 



