南海东沙群岛南侧海域的潮余流特征

Characteristics of tide and residual current south of Dongsha island in South China Sea

为分析南海东沙群岛南侧海域次表层潮余流特征,基于布放在该海区的锚碇潜标海流资料,利用T-TIDE调和函数和低通滤波等方法,实现潮流调和常数的提取和余流的分离。该海区次表层潮流分潮K1,Msm,O1,M2和Ssa为主要分潮,各分潮东分量振幅大于北分量振幅。研究表明:潮流东西向运动强于南北向;各分潮振幅随深度变化不一致,造成潮流类型在不同深度上有所变化;二月平均余流出现相对异常现象,流速相对较大,可达83.65cm/s。次表层月平均余流变化与南海季风的盛衰有较好的对应关系,季风对该海区影响可达次表层深度。结合相应的温盐数据和高度计资料发现,余流异常与经过该海区的反气旋涡有关,涡旋改变了该海区原有的水体结构。

To analyze the characteristics of subsurface tidal residual current in the south of the Dongsha sea area of South China Sea, the characteristics of tides and residual tidal current were analyzed based on Acoustic Doppler Current Profilers carried by mooring station in this region, using T-TIDE function and low-pass method. The main tides were K1, Msm, O1, M2 and Ssa, whose amplitudes on the North direction were greater than the East part in whole. The subsurface water flow kept different tidal types at different depths, caused by the difference of sub--tidal amplitudes. Residual current in February showed anomalism with a stronger magnitude which could reach up to 83.65 cm/s. The residual tidal current in sub--surface sea water had significant seasonal characteristics, which responded to the coming of summer monsoon, suggesting that the monsoon can influence the subsurface area; combining with thermohaline data and altimeter data, it is found that residual current anomalism was related to an anticyclonic eddy going through this area, which triggerred strong hydrological environment changes.