Seasonal Evolution of the Northern Yellow Sea Cold Water Mass

Based on in-situ CTD observations from 908 Project during 2006—2007,the formation and evolution of North Yellow Sea Cold Water Mass(NYSCWM) is analyzed: The NYSCWM,which appears in spring,characterizes with a 6 ℃ cold water mass covering more than 1/3 of survey region and core salinity exceeding 32 psu.The axis of 32.5 saltier tongue is found to move toward west from 124°E in winter to 123.3°E in spring off the east of Chengshantou.;In summer NYSCWM occupies the central trough of 50 m and the strength reaches its peak with a core temperature less than 6 ℃ and salinity higher than 32 psu,A two-core pattern can be identified both in temperature and salinity fields.Comparing to previous results,a eastward drift exists for the center of cold water;The two-core feature of NYSCWM still remains in autumn for temperature,but with its strength being greatly weakened.The location of higher salinity lies off 38.5°N,122.5°E;The most significant feature in vertical is a thermocline,which separate the NYSCWM from its upper water.The thermocline is found to appear in spring with a depth of 20~30 m and moves upward to 10~20 m in summer,reaching its peak in strength.In autumn it turns to a lower depth of 30~40 m and finally disappears in witner.