Collaborative Research: Heat flow mapping and quantification at ASHES hydrothermal vent field using an observatory imaging sonar

热量从地球内部进入海洋是影响海洋动力学、化学交换和海洋生命的关键因素。 然而，迄今为止，尚无法对海底热液喷口喷出的流体进行真实的长时间监测，尽管这些流体将大量的内部地热从大洋地壳深处带到海底。该项目克服了这一问题，在胡安·德富卡海岭中轴火山破火山口ASHES热液区国家科学基金会最近完成的海洋观测倡议有线观测站上安装了新测试的仪器，即有线观测站喷口成像声纳系统，能够长期监测热液喷口流体通量。这一声纳系统的设计目的是对热液排放进行成像，并测量热液排放从海底以下转移到海洋的热量。 这项工作的一个目标是继续改进该系统，并将其发展成为一个可靠的工具，用于利用声学传感长期反复量化热液活动（流体流动和热传输）。由此产生的热传输测量结果将有助于调查向周围岩石提供热量的火山系统、地下流体流动过程和生物系统之间的联系，生物系统依赖于地下水-岩石相互作用中金属和其他化合物沥滤而产生的热液系统中减少的化学物质。电缆声纳系统的第二次部署将测试其测量和耦合放电率和热传输的能力。这项工作的更广泛影响包括增加科学和应用基础设施，以监测和测量甲烷渗漏处的甲烷排放率和/或深水地平线等油井井口井喷处的石油。这项工作还将导致本科生的培训和教育与研究的一体化。还将通过讲座和媒体渠道向公众传播成果。研究耦合的地球-生物-热液系统所需的最重要的现场测量之一是热通量。这是海底热液系统的一个基本特性。它连接其驱动力（即，海底下的热源（如火山岩浆或蛇纹岩化）对它所影响的系统的影响，如化学品流入海洋。它还对地下和地表生物圈施加控制。以前为充分测量海底热液热流量所作的尝试无法以解决喷发动态所需的空间/时间综合覆盖范围和分辨率进行测量。 最近开发和测试的声纳系统将安装在国家科学基金会最近委托在胡安·德富卡海岭的ASHES热液喷口区的海洋观测倡议有线阵列上，这将使人们能够监测和量化热液排放及其从海底以下岩石向海洋转移的热量。声纳系统能够在喷口区的很大面积范围内进行天气测量，并能收集和传送长达数年的数据。这大大减少了对数据进行外推的需要。除了监测，这项研究将利用一种创新的方法反演声学数据，估计热通量的扩散流周围的通风口使用新开发的声学方法。 该仪器的部署期为4年。 它将与地面实况测量相结合，以确定聚焦流和扩散流以及温度/热通量的流速方面的声学结果的准确性。由此产生的时间序列的热通量从集中和扩散源具有广泛的适用性。特别是，热通量值和变化的动态热液喷发在ASHES及其与地震活动，岩浆供应，地壳冷却和玄武岩-水的相互作用的连接的影响。它还对海洋的热量和化学变化、海底生态系统的能源和营养供应以及地下生物圈的范围和性质产生影响。

The movement of heat from inside the Earth into the ocean is a key factor influencing ocean dynamics, chemical exchange, and life in the oceans. However, until now, it has not been possible to monitor, in real time and over long periods of time, the fluids venting from seafloor hydrothermal vents even though these fluids carry a significant amount of internal geothermal heat from deep in the ocean crust to the seafloor. This project overcomes this problem by installing newly tested instrumentation, a Cabled Observatory Vent Imaging Sonar system, capable of long term monitoring of hydrothermal vent fluid fluxes, on the National Science Foundation's recently completed Ocean Observing Initiative's cabled observatory at the ASHES hydrothermal field in the caldera of Axial Volcano on the Juan de Fuca Ridge. This sonar system is designed for imaging hydrothermal discharge and the measuring heat transferred by that discharge into the ocean from the subseafloor. One goal of the work is to continue improving the system and developing it into a reliable tool for long-term repeated quantification of hydrothermal activity (fluid flow and heat transport) using acoustic sensing. The resulting heat transport measurements will enable investigation of the connections between the volcanic system, which supplies heat to the surrounding rock; subsurface fluid flow processes; and the biological systems that depend on the reduced chemical species that emanate from the hydrothermal system as a result of the leaching of metals and other compounds from water-rock interaction in the subsurface. This second deployment of the cabled sonar system will test its ability to measure and couple discharge rates and heat transport. Broader impacts of the work include increasing infrastructure for science and applications that extend to monitoring and measuring the discharge rates of methane at methane seeps and/or oil at oil-well head blowouts such as Deep Water Horizon. The work will also result in the training of undergraduates and the integration of education and research. Results will also be disseminated to the public via lectures and media outlets. One of the most important field measurements needed for the study of coupled geo-bio-hydrothermal systems is heat flux. This is a fundamental property of seafloor hydrothermal systems. It connects its driving force (i.e., sub-seafloor heat sources such as volcanic magma or serpentinization) to the systems it impacts, such as the flux of chemicals into the ocean. It also exerts controls on the subsurface and surface biosphere. Previous attempts to adequately measure seafloor hydrothermal heat flux have been unable to measure it with the combined spatial/temporal coverage and resolution necessary to resolve the dynamics of venting. The installation of the recently developed and tested sonar system that will be installed on the National Science Foundation's recently commissioned Ocean Observatory Initiative cabled array at the ASHES hydrothermal vent field on the Juan de Fuca Ridge will enable the monitoring and quantification of hydrothermal discharge and the heat transferred by it from rocks below the seafloor to the ocean. The sonar system is able to make synoptic measurements across a significant areal extent of the vent field and can collect and transmit data for periods of up to several years. This greatly reduces the need for extrapolation in the data. In addition to the monitoring, this research will exploit an innovative method for inversion of acoustic data to estimate the heat flux of diffuse-flow around the vents using a newly developed acoustic method. Deployment of the instrument will be for 4 years. It will be combined with ground-truth measurements to establish the accuracy of the acoustic results in terms of flow rates for focused and diffuse flow and for temperature/heat flux. The resulting time series for heat flux from focused and diffuse sources has a broad range of applicability. In particular, heat flux values and variations have implications for the dynamics of hydrothermal venting at ASHES and its connections with seismicity, magma supply, crustal cooling, and basalt-water interactions. It also exerts influence on heat and chemical changes in the ocean, energy and nutritive supplies to seafloor ecosystems; and the extent and nature of the subsurface biosphere.