Seasonal variation of water column structure and sediment transport in a mud depo-center off the Zhejiang-Fujian coast in China
Seasonal variation of water column structure and sediment transport in a mud depo-center off the Zhejiang-Fujian coast in China
复制标题
浙闽沿岸泥浆堆积中心水柱结构与泥沙输运的季节变化
DOI：
10.1007/s10236-013-0620-6
复制
发表时间：
2013-06-01
期刊：
影响因子：
2.3
通讯作者：
Chen, Jian
中科院分区：
文献类型：
--
作者：
Li, Yunhai;Qiao, Lei;Chen, Jian
2008年12月和2009年8月，在东海内陆架浙闽海岸泥沉积中心（MDZFC）进行了两次调查，描绘了水柱结构的季节变化，并分析了造成这种变化的因素。并利用研究结果探讨了MDZFC的输沙过程和形成机制。在两次调查中，水柱的结构在温度、盐度和浊度方面变化很大。夏季水体温度和盐度较高，温度分层明显，盐度在整个水体中保持不变。分层限制了沉积物的再悬浮和运移。从北向南，中底水层温度略有升高，盐度基本保持不变。冬季水体温度较低，盐度较低，垂直混合较好。温度和盐度从表面到底部向东（深水区）和向南均呈上升趋势。夏季温度低、盐度高，冬季温度高、盐度高的楔形水团，从水深50 m以上开始，沿海底向陆地扩展，冬季扩展较强，呈海岸上升流形态。冬季水体浊度明显高于夏季。表层浊度冬季一般大于5 FTU，夏季一般小于1 FTU。底层浊度冬季远大于200 FTU，夏季略大于50 FTU。冬季靠近海底的浑浊水层深度可达50 m以上，厚度可达10 m以上；但夏季仅在水深30米、水深5米的水域进行。海相沉积环境的差异与水动力环境、天气条件、沉积物供给和季节环流的季节变化有关。结果表明，冬季是颗粒迁移和沉积的关键季节。底部混浊层是沉积物输运的主要通道，上升流和海锋系统在沉积过程和MDZFC的形成中起着重要作用。
Two surveys were conducted in December, 2008, and August, 2009, in the mud depo-center off the Zhejiang-Fujian coast (MDZFC) in the inner shelf of East China Sea to depict the seasonal variation of the water column structure and analyze the factors responsible for the variation. The results were also used to discuss the sediment transport process and formation mechanism of the MDZFC. The water column structures varied significantly between the two surveys, with respect to the temperature, salinity, and turbidity. The summer water body, with relatively high temperatures and salinities, was evidently stratified with respect to the temperature, whereas the salinity remained constant throughout the water column. The stratification restricts sediment resuspension and transport. From the north to the south, the temperature in the middle-bottom water layer slightly increased, whereas the salinity remained mostly constant. In winter, the water body, with relatively low temperatures and salinities, was well mixed vertically. The temperature and salinity both increased from the surface to the bottom toward the east (deep water) and the south. A wedge-shaped water mass, which appears as a coastal upwelling, with relatively low temperature and high salinity in summer and relatively high temperature and high salinity in winter, spread landward along the sea floor, from the sea deeper than 50 m, whereas the extension was relatively stronger in winter. The water turbidity in winter was clearly higher than in summer. In the surface layer, the turbidity was generally greater than 5 FTU in winter and less than 1 FTU in summer. In the bottom layer, the turbidity was much greater than 200 FTU in winter and slightly greater than 50 FTU in summer. Moreover, the turbid water layer close to the sea floor in winter can reach into an area deeper than 50 m with a thickness of over 10 m; however, it was only limited to only 30-m-deep water with a thickness of 5 m in summer. The differences of marine sedimentary environment in the MDZFC were attributed to the seasonal variations of hydrodynamics environment, weather conditions, sediment supplies, and seasonal circulations. The results suggest that winter is the key season for particle transportation and deposition. The bottom turbid layer is the primarily channel of sediment transport, and the upwelling currents and the oceanic front systems play an important role in the sediment deposit processes and the formation of the MDZFC.