南海北部琼东南海域活动冷泉流场特征初探  

A preliminary study on the active cold seeps flow field in the Qiongdongnan Sea Area, the northern South China Sea

作　　者：张锟 宋海斌[1] 王宏斌[2] 陶军[2] 关永贤[2] 龚屹 范文豪 耿明会 Kun Zhang;Haibin Song;Hongbin Wang;Jun Tao;Yongxian Guan;Yi Gong;Wenhao Fan;Minghui Geng(State Key Laboratory of Marine Geology,School of Ocean and Earth Science,Tongji University,Shanghai 200092,China;Guangzhou Marine Geological Survey,Guangzhou 510075,China)

机构地区：[1]同济大学海洋与地球科学学院,海洋地质国家重点实验室,上海200092 [2]广州海洋地质调查局,广州510075

出　　处：《科学通报》2020年第12期1130-1140,共11页Chinese Science Bulletin

基　　金：国家重点研发计划(2018YFC0310000,2017YFC0306703);“全球变化与海气相互作用”专项国际合作项目(GASI-GEOGE-05);国家自然科学基金(41976048,41576047)资助。

摘　　要：冷泉是甲烷流体运移的一种重要地质过程.作为一种重要的温室气体,海底冷泉处渗漏的甲烷流体,对全球气候变化具有重要的影响.因此,冷泉流场的研究对于冷泉地质过程和全球气候变化都具有重要的意义.本研究基于PIV(particle image velocimetry)技术,对南海琼东南海域新发现的活动冷泉视频资料进行了活动冷泉的流速流场的模拟定量研究.研究区活动冷泉的释放有两种形式:一种是天然气水合物分解形成甲烷气泡,缓慢地逸散至海水;另一种则是含甲烷流体从喷口快速喷发形成羽状流.PIV计算的结果显示,活动冷泉羽状流流场运动方向整体向上,内部为复杂的湍流,其流线呈现出蜿蜒的形态,冷泉羽状流的运动方向与流速大小均随时间的改变而改变.尽管存在一定的系统误差,但PIV计算的结果仍然是可信的,并且具有低成本、速度快、分辨率高等独特的优势.与热液流场相比,冷泉流场的研究程度相对较低,未来需要更多的工作来定量描述冷泉流场,并分析冷泉流场的变化规律.Cold seep is an important geological process of methane fluid migration. Methane plumes at these seeps have a significant impact on the local carbon budget and may trigger massive precipitation of carbonates and cold-seep biome. As a powerful greenhouse gas, methane seeping/venting from a cold seep may be released into the atmosphere and have a huge effect on climate. Research on cold seep flow field is of great significance for understanding geological processes of cold seep and their impacts on global climate change.Several methods have been used to observe cold seeps, e.g., acoustical, geochemical, and optical methods. However, no flow field image of Haima cold seeps was shown by these methods so far. The particle image velocimetry(PIV) method is a commonly used approach in the study of fluid dynamics. It tracks the motion of tracer particles in a flow field over a small time interval, so that the instantaneous velocity field can be calculated using a spatial cross-correlation method. In this study, we applied the PIV method to analyze in-situ video image sequences of the newly discovered, active cold seep in the Qiongdongnan Basin of the northern South China Sea during 2019, and obtained some quantitative, preliminary information about the flow.According to the video image sequences, there are two ways of methane seeping from the seafloor in the study area. One is via methane bubbles, which are formed through gas hydrate decomposing, and then slowly escaping from the seafloor.The other is via plumes of methane-containing fluid, which erupt rapidly from the vent. Gas hydrate-coated methane bubbles may also exist over the cold seep. The velocity of the plumes is between 0.00756 and 10.984 px/frame, and the accelerated velocity is-233.077 to 169.617 px/frame2(negative for velocity decreasing with time). The vertical velocity is-10.842 to 5.055 px/frame(positive direction for downward), and the horizontal velocity is-6.377 to 5.828 px/frame(positive direction to the right). The velocity of methane bubbles is abou

关 键 词：活动冷泉 流场 天然气水合物 粒子图像测速 

分 类 号：P744[天文地球—海洋科学]