海岸风暴频率-强度关系的沉积记录分析

The scientific question in the present proposal is how to extend the intensity-frequency curve of extreme events towards a 1000 year domain, on the basis of sedimentary archive analysis. The return period of any extreme events is an important parameter for coastal design-flood levels, which used to be estimated using the data of a 100 year scale measured by instruments. Furthermore, the factors of climate and sea level changes were often neglected. Here, we attempt to obtain the information on event beds, using the high resolution sedimentary records from the Jiangsu and Hainan Island coastlines. Then, a sediment dynamic approach is adopted to link each of the bed with the intensity of storms, together with the return periods. As such, the intensity-frequency curve of a thousand year scale can be defined. The theoretical significance of the study lies in an improved understanding of the process-product relationship of the earth system. Sedimentary records provide critical information on climate, earth surface morphology and ecosystem changes; since the monitoring of the earth system has only a relatively short history, i.e., the time series have a limited length, it would be desirable to develop new techniques to analyze the sedimentary record. On the application side, the research proposed may be applied to the design of coastal engineering schemes with an enhanced standard, in response to the increasingly concentration of the population towards the coastlines and future threats of sea level rise and intensified extreme events.

本项目的科学问题是如何根据沉积记录将极端事件重现期曲线推进至千年时间尺度。极端事件重现期是海岸防护工程设计的依据，然而以往的频率-强度曲线是根据器测时代（过去百年左右）的数据确定的，且气候和海面变化因素未能充分考虑。本项目以高分辨率的江苏和海南岛海岸沉积记录为载体，提取所含的风暴事件信息，再根据沉积动力过程模拟，确定每个风暴层所对应的风暴强度以及相应的重现期，由此可将频率-强度曲线的定义域扩展至千年尺度。本项目对于地球系统过程-产物关系研究具有理论意义。沉积记录是地球历史档案库，是了解气候、地貌环境和生态系统演化的重要信息来源，目前获得的器测数据在时空尺度上的覆盖度十分有限，因此有必要深入挖掘沉积记录信息。本项研究成果可应用于防护标准提高后的海岸工程设计，随着人群和生产力向沿海地区的集聚，再加上气候和海面变化的影响，海岸带城市和海港等重要基础设施防护标准的提高已迫在眉睫。

本项目拟深入挖掘沉积记录，使之成为了解气候、地貌和生态系统变化的重要信息来源；应用目标是建立千年时间尺度的风暴强度-频率曲线，为未来海面上升、风暴加剧的海岸防护工程提供科学依据。研究内容是：江苏和海南岛海岸的台风记录特征；风暴沉积记录形成的数值实验；沉积记录中的风暴强度和频率信息提取；器测记录与沉积记录复合的风暴强度-频率关系曲线重建。5年来，获得了基础数据集，梳理了风暴大浪对海岸沉积动力过程的影响，进行风暴浪-增水条件下物质输运堆积的数值计算，进行风暴沉积记录形成的数模实验，从钻孔记录中建立长周期风暴强度-频率关系，并评价其与气候变化的关系。研究结果发表于Marine Geology、Sedimentary Geology、Sedimentology、Continentl Shelf Research、Geological Society of America Bulletin、Acta Oceanologica Sinica等刊物。后续论文将涉及风暴沉积模拟的“解空间收缩法”、典型区域的风暴强度-频率关系曲线、气候变化对风暴的影响等。本项目可应用与绿色海岸工程领域；培养年轻学者十多人，其中2人已获青年基金项目资助。