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

合作研究：使用天文台成像声纳对 ASHES 热液喷口场进行热流测绘和量化

• 批准号: 1736621
• 负责人: Leonid Germanovich
• 金额: $ 1.58万
• 依托单位: Georgia Tech Research Corporation
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2017
• 资助国家: 美国
• 起止时间: 2017-08-15 至 2019-07-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1736621&HistoricalAwards=false
• 关键词: Collaborative; Research; Heat; flow; mapping

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.

从地球内部进入海洋的热量是影响海洋动力学，化学交换和海洋生命的关键因素。 然而，到目前为止，即使这些液体携带大量的内部地热热，从海底的海壳深处到海底。该项目通过安装新测试的仪器（一种有线观测机排气成像声纳系统，能够长期监控水热通风液通量，在国家科学基金会最近完成的海洋观察计划的船上的船上启动天文台上安装新测试的仪器，以克服了这个问题。该声纳系统的设计用于成像水热放电，并通过从子层面的海洋中传递到海洋中的测量热。 这项工作的一个目标是继续改善系统，并将其开发为可靠的工具，用于长期重复量化水热活动（流体流量和热传输）。由此产生的热传输测量值将能够研究火山系统之间的连接，该火山系统向周围的岩石提供热量。地下流体流动过程；以及依赖于从热液系统中散发出的化学物质的生物系统，这是由于金属的浸出和其他化合物从地下中水摇滚相互作用而产生的。有被有线的声纳系统的第二次部署将测试其测量和配对排放率和热传输的能力。这项工作的更大影响包括增加对科学的基础设施和应用，这些基础设施扩展到监测和测量甲烷渗漏处甲烷的排放率和/或在油井头部井喷时（例如深水地平线）的排放率。这项工作还将导致对大学生的培训以及教育和研究的整合。结果还将通过讲座和媒体传播给公众。研究耦合地理生物热热系统所需的最重要的现场测量之一是热通量。这是海底水热系统的基本特性。它将其驱动力（即火山岩浆或蛇形化的下层状热源）连接到其影响的系统，例如化学物质向海洋的通量。它还在地下和表面生物圈上施加控制。先前试图通过空间/时间覆盖的组合和分辨率来解决通风动力学所必需的空间/时间覆盖范围和分辨率。 新近开发和测试的声纳系统的安装将安装在国家科学基金会最近委托的海洋天文台计划中，该计划在Juan de Fuca Ridge的Ashes Hydrothermal Vent场上有线阵列，将使水热放电的监测和量化能够监测和量化。声纳系统能够在通风口场的显着范围内进行概要测量，并可以收集和传输数据长达几年的时间。这大大减少了数据中推断的需求。除了监测外，这项研究还将利用一种创新的方法来反转声学数据，以使用新开发的声学方法估算通风孔周围漫射流的热通量。 该工具的部署将持续4年。 它将与地面真实测量值结合使用，以建立在聚焦和弥漫流动以及温度/热通量的流速方面的声学结果的准确性。来自聚焦和分散源的热通量的最终时间序列具有广泛的适用性。特别是，热通量值和变化对灰烬排气的动力学及其与地震性，岩浆供应，地壳冷却和玄武岩 - 水相互作用的连接具有影响。它还对海底生态系统的海洋，能源和营养用品的热和化学变化产生影响；以及地下生物圈的程度和性质。