Thermal and haline fronts in the Yellow/East China Seas: Surface and subsurface seasonality comparison

Abstract

Seasonal variability of surface and subsurface thermal/haline fronts in the Yellow/ East China Seas (YES) has been investigated using three-dimensional monthly-mean temperature and salinity data from U.S. Navy’s Generalized Digital Environmental Model (Version 3.0). The density-compensated Cheju-Yangtze Thermal/Haline Front has (northern and southern) double-tongues. The northern tongue is most evident throughout the depth from December to April. The southern tongue is persistent at the subsurface with conspicuous haline fronts. The thermal (haline) frontal intensity of the northern tongue is controlled mainly by the temperature (salinity) variation on the shoreward (seaward) side of the front. The cold water over the Yangtze Bank is influential in generating the southern tongue and intensifying the Tsushima Thermal Front. The year-round Cheju-Tsushima Thermal Front is evident throughout the depth and intensifies from July to December. The northern arc of the Yangtze Ring Haline Front is manifest in spring and is sustained until summer, whereas the southern one is fully developed in summer because of eastward migration of the Yangtze Diluted Water. The area showing strong frontal intensity in the Chinese Coastal Haline Front shifts seasonally north and south along the Zhejiang-Fujian coast. The Generation and evolution of YES fronts are closely associated with YES circulation (inferred from the linkage of the water masses). Moreover, the subsurface temperature/salinity evolution on the fronts in the Yellow Sea differs from that in the East China Sea owing to local factors such as wintertime vertical mixing and a summertime strong thermocline above the Yellow Sea Bottom Cold Water.