潮汐环境中千年尺度风暴强度的沉积记录解译

This project focuses upon the response of the sedimentary records to the millennium-scale storm intensity, taking the central Jiangsu coast as the key study area, and the hypotheses of the corresponding relationship between event bed and storm intensity will be tested. Based on the methods of sedimentology, environmental magnetism and geochemistry, the characteristic difference between normal tidal deposit and storm deposit will be analyzed, and the effective proxies for storm record identification will be established. The age of the storm will be determined based on chronological analysis. The processes of transport and accumulation under storm surge conditions will be analyzed based on integrated field measurements. Then, a sediment dynamic approach is adopted to model the spatial distribution patterns of tidal flat accretion /erosion，under both fair weather and storm surge conditions, taking Typhoon No.8114 as a case using Delft3D. As such, the relationship between storm deposit and storm intensity at different elevations or depths can be established, and then each of the event bed with the intensity of storms, together with the return periods can be defined. The scientific data sets obtained will be beneficial to a better understanding of the formation processes of sedimentary sequence of extreme events, and can also help to promote the development of simulation technology in the field of sedimentology.

以江苏中部海岸为研究区，探讨千年尺度风暴强度的沉积记录响应规律，验证关于风暴沉积与风暴强度的对应关系的假说。综合运用沉积学、环境磁学和地球化学等方法，根据正常潮汐沉积与风暴沉积的差异特征，建立风暴记录识别的有效替代指标，并根据年代分析，确定风暴层年龄。应用现场沉积动力学观测方法，分析极端天气下的物质输运和堆积的动力过程和机理；选取近 50 年来对江苏海岸影响最严重的 8114 号强台风为风暴潮事件，采用Delft3D模型来模拟正常天气和台风期间潮滩沉积的形成过程和空间分布，建立同一个台风在潮滩不同高程上形成的沉积记录，对同等高程的记录进行对比，建立不同高程或水深条件的风暴沉积与风暴强度的对应关系，进而计算地层中逐个风暴沉积所对应的风暴强度及相应的重现期，用以解释千年尺度风暴强度的沉积记录。上述研究有助于深入认识极端事件沉积记录的形成过程，增进沉积学模拟技术的发展。

海岸带面临着多种自然灾害风险，其中台风灾害发生频率最高、影响最严重，受到科学界的广泛关注。由于台风器测年限太短，气候和海面变化因素未能充分考虑，对长时间尺度的台风活动规律（频率和强度）及其气候驱动机制认识不足。本项目选择江苏潮滩为代表性的海岸沉积记录，通过运用多学科交叉方法，建立了潮滩不同部位风暴记录识别的有效替代指标并提取了风暴发生的频率信息。应用沉积学和沉积动力学模拟方法，改进了平流-沉降模型Advective-settling model），建立了潮滩不同高程风暴沉积与风暴强度的一一对应关系，定量重建了江苏海岸近5000年的台风强度-频率曲线。该曲线表明台风频率-强度曲线不仅在不同时间尺度变化，而且在同一时间尺度也可能存在变化。在此基础上，厘清了江苏海岸千年尺度台风活动的气候驱动机制：ENSO-亚洲季风-西太平洋暖池温度。本研究有助于丰富和发展古风暴学和沉积动力学的研究方法和理论，提高台风强度-频率关系的预测能力，为气候变化和人类活动背景下的海岸带蓝图重绘提供科学依据，保障河口海岸地区对经济社会发展支撑力的可持续性。