On southern movement and seasonal variation of Tsugaru Warm Current.

Abstract

The seasonal variation patterns on the relationship between the size of eastward expanding gyres and southward current velocity concerning Tsugaru Warm Current (T.W.C.) had been clarified by many oceanographic data of Sanriku coastal area during past decade. The expanding gyres can be categorized in 4 types by monthly 100 m temperature maps and the southward current velocity of T W C. is also classified by GEK data in the same 4 types. Regarding gyre patterns, the smallest gyre and southward current near the coast of Shimokita Peninsula from January to May, named coastal mode by Conlon (1982), is called coastal type (Type C ) in this paper Likewise， medium expanded size gyre from June to July is called medium gyre type (Type GM); most enlarged size gyre from August to November, large gyre type (Type GL); and large gyre transferring to Type C from November to December, transition type (Type T). On the other hand, regular seasonal variation of mean velocity of southward Sanriku Coastal current is observed 0.5 -0.6 knots from January to May, about 0.7 knots from June to Jury, 121.3 knots from August to November and about 0.8 knots from November to December corresponding to the above 4 types respectively. The ocean state of Sanriku coastal area Is greatly affected by T.W.C. Then, it is Important to know both regularity and irregularity of T.W.C. because it Is necessary to predict the variation of the Oyashio which have great influence on ocean state, local climate and various environments of Tohoku district.