闽浙沿岸泥质沉积中心台风沉积过程及其地质记录研究

Being one of the strongest atmospheric-marine interacting processes in term of changing the marine environment, the typhoons effect the sedimentary processes drastically through intensive transport, mixing and resuspension of particles during a relatively short time period, resulting in significant geomorphologic and ecological change of the shelf regime. The mud depo-center off the Zhejiang-Fujian coast (MDZFC) acts as a sink for Changjiang River particles and accounts for the primary mud deposits on the East China Sea inner shelf, containing abundant of marine environment changes and geological information. At the same time, being located in the typhoon-prone region, the MDZFC is an ideal region to study the typhoon sedimentary processes. This project plans study the deposition processes and their geological records related to typhoon processes in the MDZFC. Based on the comparative analysises of the sedimentary environment and their variations in time and space scales, including water, paticles, surface sediment and sedimentary bodies, the impacts of typhoon on the whole sedimentary system at different stages of typhoon processes will be studied. To which extend the typhoon would affect on the sedimentary systems will be evaluated with influencing mechanism addressed. In the accurate identification of typhoon sedimentary sequence, sedimentary geological record of typhoon will be revealed. The researches are of importance on determining particles diffusion and exchange between seawater and sediment, completely uncovering sedimentary dynamic process and the sedimentary geological records.

台风是天气尺度上对海洋环境影响最大的海气相互作用之一，对海洋沉积过程有不可忽视的影响。闽浙沿岸泥质区是我国陆架海泥质沉积体系的组成部分之一，蕴含了丰富的海洋环境和地质信息。同时，泥质区处于台风多发地带，是台风沉积过程研究的理想海域。本项目拟在闽浙沿岸泥质沉积中心开展台风沉积过程及其地质记录的研究。将海水-颗粒物-浅层沉积物-沉积体作为一个沉积体系，基于台风不同阶段对沉积体系的沉积环境及其时空演化的对比分析，研究台风对沉积体系的影响过程，评价其影响程度，阐述其影响机制；在准确识别台风沉积层序的基础上，探讨台风沉积的地质记录。本研究对海洋物质交换、沉积动力过程、沉积地质记录等研究都有重要意义。

根据课题的研究内容和目标，结合台湾海峡及其周边海域台风过程的实际路径及其影响范围，对2009～2015年间的8次台风（热带风暴）过程开展了多次野外调查和数据资料收集，获得了大量的海洋环境数据和样品。对这些数据和样品进行了综合分析，取得了如下认识：1）台风对近岸水体叶绿素分布有显著影响。叶绿素含量在台风直接影响下显著降低，直接影响结束后急剧增加。这是对水体混合、强降雨、高营养盐输入等的综合响应；2）台风导致悬浮颗粒物粒级分配发生显著变化，水体中细颗粒组分含量增加，粗颗粒组分含量相对降低，平均粒径总体降低，这是对表层沉积物再悬浮，水体中生物组份降低，大颗粒破损等的综合响应；3）利用高分辨率浅地层剖面探测技术和放射性同位素方法探测台风苏拉形成了约20cm厚的风暴沉积层。沉积层厚度、沉积物粒度、δ13C值分布显示沉积层的物质主要来源于海底沉积物的再悬浮和再分配；4）台风引起了水体硅藻-沉积物中生源硅的分布变化，台风后表层沉积物中生源硅含量比台风前正常海况下的要高，是生源硅物质来源和海洋动力环境变化造成的；5）台风期间卫星遥感数据显示，台风过程会引起台湾海峡上升流的发育，同时，台风期间河流入海泥沙增加以及海底沉积物再悬浮增加了水体悬浮颗粒物含量，相对高泥沙含量水体在风致流携带下向海峡中部输运，可能是海峡两岸物质交汇，台湾海峡中部泥质带形成的重要动力机制之一；6）海底潜标对粤东上升流发育过程的连续观测发现粤东海域上升流的发育过程与季风相关。热带风暴泰利和杜苏芮期间的风场导致表层水体Ekman输运为向岸方向，阻碍了海水的离岸输运，从而破坏了整个水体流场结构，导致上升流系统的破坏。风暴过后，水体流场迅速恢复，上升流系统重新形成。.在此基础上撰写论文十余篇（其中发表SCI论文7篇，中文核心期刊论文3篇，投稿SCI论文4篇），在国内外学术会议上多次做报告交流。较好地完成了课题的任务，达到了预期目标。