We investigated the short-period variations in vertical fluxes of hydrothermal plumes at mid-ocean ridges through quantitative analysis of digital video images of plumes using the particle image velocimetry method. The analyzed digital video images of hydrothermal plumes were selected from the V Vent and Biotransect Vent at the fast-spreading East Pacific Rise, the Grotto Mound of the Endeavour Segment at the intermediate fast-spreading Juan de Fuca Ridge, and the TAG vent at the slow-spreading Northern Mid-Atlantic Ridge. The PIV was able to track the motion of turbulent parcels instead of individual particles within a hydrothermal plume. The mean plume vertical flux was shown to increase with increasing height above the vent orifice, revealing significant turbulent disperse of the rising hydrothermal plumes. The dominant periods of oscillation in the mean vertical flux were observed to be within a relatively narrow band width of 0.5–5 s despite diverse geological settings. Such pervasive short-period variations in plume flux are hypothesized to be caused by the pressure-drop oscillation within a network of compressible two-phase fluid within a sub-seafloor hydrothermal source zone. It is further argued that both the period and amplitude of plume flux oscillation might increase with decreasing plume vertical flux. The relatively narrow band width of the observed oscillation periods might reflect common characteristics in the plume dynamics despite diverse geological settings.

中文翻译：

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大洋中脊热液羽流垂直通量随时间的变化

我们通过使用粒子图像测速法对羽状流的数字视频图像进行定量分析，研究了洋中脊热液羽状流垂直通量的短期变化。分析的热液羽流的数字视频图像选自快速扩展的东太平洋上升带的V型通风口和Biotransect通风口，中间快速扩展的Juan de Fuca山脊处的奋进段岩溶丘和TAG通风口。大西洋北部中脊缓慢扩展。PIV能够跟踪湍流包裹的运动，而不是跟踪热液羽流中的单个粒子。结果表明，垂直羽流的平均通量随排气孔上方高度的增加而增加，从而揭示出上升的热液羽流的明显湍流分散。尽管地质条件不同，但平均垂直通量的主要振荡周期仍在0.5-5 s的较窄带宽内。羽状通量的这种普遍的短周期变化被认为是由海底热液源区内可压缩两相流体网络内的压降振荡引起的。进一步认为，羽流通量振荡的周期和幅度都可能随着羽流垂直通量的减小而增加。尽管地质条件多种多样，但观察到的振荡周期的相对较窄的带宽可能反映了羽流动力学的共同特征。羽状通量的这种普遍的短周期变化被认为是由海底热液源区内可压缩两相流体网络内的压降振荡引起的。进一步认为，羽流通量振荡的周期和幅度都可能随着羽流垂直通量的减小而增加。尽管地质条件多种多样，但观察到的振荡周期的相对较窄的带宽可能反映了羽流动力学的共同特征。羽状通量的这种普遍的短周期变化被认为是由海底热液源区内可压缩两相流体网络内的压降振荡引起的。进一步认为，羽流通量振荡的周期和幅度都可能随着羽流垂直通量的减小而增加。尽管地质条件多种多样，但观察到的振荡周期的相对较窄的带宽可能反映了羽流动力学的共同特征。