Characteristics of thermal finestructure in the southern Yellow Sea and the East China Sea from airborne expendable bathythermograph measurements |
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Authors: | Sunghyea Park Peter C Chu |
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Institution: | (1) Department of Oceanography, Naval Postgraduate School, Monterey, CA 93943-5001, USA |
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Abstract: | Four surveys of airborne expendable bathythermograph with horizontal spacing of about 35 km and vertical spacing of 1 m extending
from the surface down to 400 m deep are used to analyze thermal finestructures and their seasonality in frontal zones of the
southern Yellow Sea and the East China Sea. Finestructure characteristics are different not only among fronts but also along
the same front, implying different mixing mechanisms. Summer thermocline intrusions with thickness from few to 40 meters,
generated by the vertically-sheared advection, are identified along the southern tongue of the Cheju-Yangtze Front (especially
south of Cheju Island). The finestructures south of the Yangtze Bank (i.e. the western tip of the southern tongue) produced
by strong along-frontal currents are not as rich as elsewhere in the southern tongue. The Cheju-Tsushima Front presents mixed
finestructures due to confluent currents from various origins. The irregular-staircase finestructures in the Kuroshio region
(below the seasonal thermocline), driven by double-diffusive mixing, show seasonal invariance and vertical/horizontal coherence.
The strength of mixing related to finestructure is weaker in the Kuroshio region than in the Cheju-Tsushima Front or south
of Cheju Island. The profiles in the Tsushima Warm Current branching area show large (∼50 m thick), irregular-staircase structures
at the upper 230 m depth, which coincides roughly with the lower boundary of the maximum salinity layer. The finestructure
at depths deeper 230 m is similar to that in the Kuroshio region. The possible mechanisms for generating the finestructures
are also discussed. |
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Keywords: | Yellow/East China Seas AXBT synoptic thermal fronts thermal finestructures mixing |
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