Thermal Fronts and Cross-Frontal Heat Flux in the Southern Yellow Sea and the East China Sea

摘要

Synoptic features in/around thermal fronts and cross-frontal heat fluxes in the southern Yellow Sea and East China Sea (YES) were examined using the data collected from four airborne expendable bathythermograph surveys with horizontal approximately 35 km and vertical 1 m (from the surface to 400 m deep) spacings. Since the fronts are strongly affected by YES current system, the synoptic thermal features in/around them represent the interaction of currents with surrounding water masses. These features can not be obtained from climatological data even with frontal analysis. The identified thermal features are listed as follows: (1) multiple boundaries of cold water, asymmetric thermocline intrusion, locally-split front by homogeneous water of approximately 18 C, and mergence of the front by the Taiwan Warm Current in/around summertime southern Cheju Yangtze Front and Tsushima Front; (2) springtime frontal eddy-like feature around Tsushima Front; (3) year-round cyclonic meandering and summertime temperature-inversion at the bottom of the surface mixed layer in Cheju-Tsushima Front; and (4) multi-structure of Kuroshio Front. In Kuroshio Front the mean variance of vertical temperature gradient is an order of degree smaller than that in other YES fronts. The southern Cheju-Yangtze Front and Cheju-Tsushima Front are connected with each other in the summer with comparable cross-frontal temperature gradient. However, cross-frontal heat flux and lateral eddy diffusivity are stronger in the southern Cheju-Yangtze Front. The cross-frontal heat exchange is the largest in the mixing zone between the modified Yellow Sea Bottom Cold Water and the Tsushima Warm Current, which is attributable to enhanced thermocline intrusions.