强台风触发深海浊流垂直结构的高分辨率锚系观测研究

Turbidity currents are the most important process in transporting sediment from the shallow shelf to the deep sea. Recently, super typhoons are considered as the crucial trigger for the frequent deep-sea turbidity currents. However, the vertical structure of deep-sea turbidity currents remain unsolved due to a scarcity of in situ observation with high resolution. Here, we focus on a unique sediment-routing system along the Gaoping River-the Gaoping Submarine Canyon off southwestern Taiwan, where typhoon-triggered deep-sea turbidity currents have frequently been identified. We plan to deploy a comprehensive mooring system in the thalweg of the middle canyon with a large seafloor slope. This mooring system is equipped with McLane moored profiler, sediment trap, and current meter with various probes. The high-resolution evolution/variability in the vertical profile of turbidity currents will be directly monitored, including velocity, temperature, salinity, pressure, turbidity, density and dissolved oxygen. Meanwhile, time-series vertical sediment flux, clay mineral assemblages, and organic carbon content are analyzed from the particles collected by the trap. The combined hydrological data and time-series sediment particles will help to clarify how the vertical structure of turbidity currents regulates the sediment resuspension/deposit in the deep sea. Through the study of this project, it is expected to improve the theoretical model of turbidity currents-controlled sedimentary process. This contributes to go a step further for the integrated study of deep-sea sedimentary dynamic process.

浊流是沉积物从陆架到深海大规模输运的最重要过程，强台风是触发深海浊流频繁发生的重要机制，但由于缺乏高分辨率海底现场观测，对于频发的深海浊流过程及其垂直结构知之甚少。台湾西南部的高屏海底峡谷频繁发生深海浊流事件，是研究强台风触发深海浊流过程的理想区域。本项目选择高屏海底峡谷中游坡度最大的深海区域，针对强台风过境台湾触发的深海浊流，布放自主爬升系缆剖面仪和沉积物捕集器综合锚系观测系统，开展深海浊流过程的高分辨率现场观测，研究深海浊流多参数垂直结构的时间序列变化，包括流速、温度、盐度、压力、浊度、密度和溶解氧等剖面，分析悬浮沉积物的通量、粘土矿物、有机碳碎屑粒度等成分的时间序列变化，预期将揭示深海浊流垂直结构的时空演化过程及其对沉积物再悬浮/沉积的调控机理。通过本项目研究，有望完善深海浊流沉积过程的理论模式，促进我国深海沉积动力过程观测研究的跨越式发展。

浊流是沉积物从陆架到深海大规模输运的最重要过程，强台风是触发深海浊流频繁发生的重要机制，亟需高分辨率多参数现场观测台风致深海浊流沉积动力过程及其垂直结构，为定量评估河流陆源沉积物从陆向海的搬运及沉积过程提供数据和理论基础。本项目原计划选择高屏海底峡谷中游坡度最大的深海区域，针对强台风过境台湾触发的深海浊流，布放自主爬升系缆剖面仪和沉积物捕集器综合锚系观测系统，开展深海浊流过程的高分辨率现场观测，但实际执行过程中因设备维修及疫情防控等原因，锚系航次未能按计划完成。结合前期深海浊流定点长期连续观测数据、卫星观测、数值模拟、浊流沉积岩心结果，项目着重分析台风致河流径流量激增而触发深海浊流的水文动力特征，评估该类型深海浊流对海洋有机碳、微塑料等颗粒物的搬运贡献；探讨不同台风触发深海浊流的剪切、浮力通量及其对盐度、沉积物的卷夹效应；厘清台风、梅雨季由于河流径流量激增和地震触发的深海浊流之间的水文特征差异，对比分析不同触发机制下深海浊流水文特征的区别及其不同的沉积物搬运作用。项目评估了深海浊流为深海岩石成因有机碳来源提供最重要的搬运机制，也是海洋微塑料等颗粒物从陆向海搬运的重要动力过程，而且台风致深海浊流沉积特征为研究古气候变化提供典型的沉积证据。