2012年南海西北陆架冬季水文特征的观测分析

OBSERVATION OF HYDROGRAPHIC CHARACTERISTICS OF NORTHWESTERN SHELF OF THE SOUTH CHINA SEA IN WINTER 2012

本文基于2012年12月南海西北部陆架海区的温盐和流速实测资料,分析了粤西和琼东陆架海区冬季三维温、盐结构和流场特征,给出沿陆架和跨陆架方向的水体和热盐通量。结果表明:(1)在50m以浅,粤西和琼东海区温度均由近岸向外海递增,深层则相反;冬季近岸海区混合层较深,外海密度跃层位于60—120m深度且层结较强,浮力频率大于10^(–2)/s;(2)海流大致沿等深线向西南流动,30m以深流速大小在0.03—0.40m/s之间,且随着深度增加而略有减小;琼东海区100m等深线附近在60m以浅水层观测到水体辐聚并有明显温度锋面存在;(3)沿陆架方向的水体和热盐输送均大于跨陆架方向,其中粤西单位面积沿/跨陆架水体通量平均值为0.13×10^(–6)/0.03×10^(–6)Sv/m^2,低于琼东海区的0.91×10^(–6)/0.56×10^(–6)Sv/m^2。

In-situ conductivity-temperature-depth （CTD） and Acoustic Doppler Current Profiler （ADCP） observations were conducted on the northwestern continental shelf of the South China Sea in December 2012. The 3-D structures of hydrographic and current properties, and alongshore and cross-shelf transports in the west Guangdong （WG） and east Hainan （EH） in winter were analyzed. The results show that the seawater temperature increased in the offshore direction in the upper layer above 50 m but decreased in deeper layers. The waters inshore were well mixed to bottom near WG coast, and the pycnocline deepened to 60--120m with stratification larger than 10-2/s in deep water offshore. The currents flowed generally southwestward along the isobaths in the magnitudes of 0.03--0.40m/s. The velocities decreased generally with depth. In the EH area, the currents above 60m converged along the 100-m isobath and formed a thermal front. The alongshore transports of water mass, heat, and salinity were larger than those of the cross-shelf. The average alongshore and cross-shelf fluxes in the WG area were 0.13x 10-6 and 0.03- 10-6Sv/m2, respectively, lower than those of the EH area for 0.91 - 10 -6 and 0.56x 10-6Sv/m2.