南海北部沙波区海底强流的内波特征及其对沙波运动的影响  

Internal-wave characteristics of strong bottom currents at the sand-wave zone of the northern South China Sea and its role in sand-wave motion

作　　者：夏华永[1] 刘愉强[1] 杨阳[1] 

机构地区：[1]国家海洋局南海工程勘察中心,广东广州510300

出　　处：《热带海洋学报》2009年第6期15-22,共8页Journal of Tropical Oceanography

基　　金：国家高技术研究发展(863)计划海洋技术领域重点项目(2008AA09A401)

摘　　要：2008年3月6日至2008年4月9日,在南海北部外陆架与陆坡上的沙波区进行了海底流速的连续观测,观测结果表明潮流与海流较弱,但时有流速达30—77cm·s-1的海底强流发生。强流方向与南海北部内波传播方向相对应,多分布在偏NW向与偏SE向。偏SE向流强于偏NW向流,与内波在传播方向上的下坡流大于上坡流的特征一致。对流速序列进行了旋转功率谱分析,结果表明,高于M2分潮的频率中,众多的振荡分量具有内波流性质,说明阵发性强流为内波所致。采用观测流速计算了沙波的移动速度,计算结果得出强流能起动海底泥沙,由于NW向传播(上坡方向)的内波导致了SE向(下坡方向)的净流动,沙波偏SE向移动,但沙波移动速度不大,小型沙波移动速度小于1.6m·a-1。采用潮流、风暴潮耦合模型计算了强台风驱动的海底流速过程,表明潮流、风暴潮耦合也能移动海底沙波,但沙波移动方向与台风路径相关,不一定为SE向,且移动距离更小,潮流、风暴潮耦合不是沙波移动的主要动力机制。From the 6th March to the 9th April in 2008, serial bottom-current observations were carried out at the sand-wave zone of the continental shelf and slope in the northern South China Sea （SCS）. The measurements show that the tidal current and ocean current are weak at the observation sites, but bottom currents as strong as 30-77 cm- s-I occur frequently. The directions of the strong bottom currents are related to the northwestward propagation of the internal waves in the region. Most of the strong currents are nearly northwestward or nearly southeastward, and the southeastward currents are stronger than the northwestward ones, which corresponds to the feature of downslope flows stronger than upslope ones when internal waves propagating onshore. Rotary power spectral analysis is carried out for the time series of current velocity. The results show that most of the rotary components higher than the frequency of M2 tide have the characteristics of internal-wave flows, further demonstrating that the frequent, strong bottom currents are induced by internal waves. The measurements are used to calculate the motion speed of sand waves. The results also show that the strong currents can initiate the sea bottom sediments, and due to downslope flows stronger than upslope ones, the sand waves move southeastwards at a low speed less than 1.6 m ·yr-1. In addition, the authors model the coupled tide-storm bottom current fields in the northern SCS. From the modeling, the bottom currents, driven by strong typhoon and tide, can move the sand waves, but only move them a very short distance during each typhoon process. The direction of the movement is subject to the typhoon route, which is not always southeastward. Therefore, the coupled tide-storm currents are not the major factor to move the sand waves.

关 键 词：南海北部 海底强流 内波 沙波移动 

分 类 号：P731[天文地球—海洋科学]