Study on the Boundary Mixing and Intrusion of Shelf Water into the Intermediate Layr of the Kuroshio around the Continental Shelf Break

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During 10 to 12 November, 1995, vertical profiles of temperature, salinity and turbidity were obtained along a cross-shelf section near the continental shelf break in the East China Sea. High turbidity water was detected just above the bottom at most of the measuring stations. And relatively high turbidity water could be detected in the intermediate layr of the slope region, which distributed along an isopycnal surface on the section, suggesting that the high turbidity water just above the bottom of the shelf should intrude into the Kuroshio. From the observations with short spacing in observation points in November, 1996, it was found that distinct evidence of intrusion of low salinity water from the shelf area into the Kuroshio. However, in 1996, origin of the low salinity water seemed to not be located near the bottom of the shelf but originated around surface layr in the shelf region, and there were no significant distinction in turbidity in the intruded water. The structure of the intrusion did not change so much between two sections with 5 miles distance in down stream direction of the Kuroshio, which indicated that the along-shelf scale of the intrusion would be larger than 10 km at least.Another measurements with current meters moored at 250m water depth around the shelf break detected internal waves with several kinds of time scale. In two days mooring with 1 minute sampling interval in November 1995, internal tide, short time scale internal waves with the several periods from 10 to 30minutes along with shorter time scale turbulent fluctuations were seen intermittently from current meters at 120 and 60m above the bottom. Although it was not clear how the internal waves related to turbulence or vertical mixing, above mentioned intrusion could be generated by frequent occurrence of turbulence or breaking of small scale internal waves.