CAREER: Development of a broadband acoustic system for quantifying the flux of free gas in methane seeps

在该CAREER提案中，PI要求提供资金，以开发宽带声学系统，以量化甲烷渗漏中的深度相关气泡尺寸分布和气体空隙率，并测量甲烷气体逸出海底和通过水柱上升的通量。这些量的声学测量的反演将通过观察气泡在宽频率范围（1-100 kHz）的响应来利用气泡的机械共振。声学系统将在其大部分频率范围（10-100 kHz）内采用恒定波束宽度换能器，以便准确处理具有不同尺寸分布的气泡羽流，这些气泡羽流在空间上非常接近，正如有时观察到的那样。该系统将被设计成集成到深水遥控潜水器中，并在全海洋深度运行。将建立第二种操作模式，在这种模式下，该系统可以从一艘机会船上拖走，作为更快速、更大规模声学调查战略的一部分。 宽带声学系统的开发和使用可以直接解决有关甲烷气泡逸出海底的命运和演变的假设。使用拟议的系统有可能提供变革性的结果，包括：1）精确估计从海底逸出的甲烷的全球通量，2）增加对海洋作为甲烷汇的能力的了解，和3）拟议的仪器提供的数据可能对更广泛的科学研究有相当大的好处，社区甲烷渗漏被认为会影响海洋化学、海洋微生物生命和大气化学，对海洋生产力、大气中的辐射平衡和古气候研究产生影响。关于这些渗漏的基本信息缺乏，拟议的文书可以为填补我们认识上的这一漏洞作出重大贡献。一些本科生和研究生将受益于帮助开发和测试新设备的经验。让本科生为学校的回声探测器套件做开发工作的想法是非常好的。外展部分将接触到当地几所学校的学生，并得到当地教师和新罕布什尔州海洋赠款的书面支持。与工业界、海洋赠款基金会和其他机构的合作提供了证据，证明该项目将产生广泛和持久的影响，许多其他科学家认为这是一个重要的问题，也是解决问题的好方法。

In this CAREER proposal the PI requests funding to develop a broadband acoustic system to quantify the depth dependent bubble size distribution and gas void fraction in methane seeps, and to measure the flux of methane gas escaping the seabed and rising through the water column. Inversion of acoustic measurements for these quantities will exploit the mechanical resonance of bubbles by observing the bubbles response at a wide range of frequencies (1-100 kHz). The acoustic system will employ a constant beamwidth transducer for much of its frequency range (10-100 kHz) in order to accurately treat bubble plumes with different size distributions that are in close spatial proximity, as is sometimes observed to happen. The system will be designed to integrate into a deepwater remotely operated vehicle (ROV) and to function at full ocean depth. A second operational mode will be established where the system can be towed from a ship of opportunity as part of a more rapid, wide-scale acoustic survey strategy. The development and use of a wideband acoustic system can directly address hypotheses about the fate and evolution of methane gas bubbles escaping the seabed. The use of the proposed system has the potential to provide transformative results including 1) refined estimates of the global flux of methane escaping the seabed, 2) increased understanding of the oceans capacity as a methane sink, and 3) estimates of the global flux of methane reaching the atmosphere from seabed seeps.Broacer ImpactsThe data provided by the proposed instrument could be of considerable benefit to the wider scientific community. Methane seeps are thought to affect ocean chemistry, ocean microbial life and atmospheric chemistry, with consequences for ocean productivity, radiation balance in the atmosphere and paleoclimate studies. Basic information on these seeps is lacking, and the proposed instrument could make a significant contribution to plugging this hole in our understanding. Several undergraduate and graduate students would benefit from the experience of helping with the development and testing of a novel device. The idea of having undergraduates do the development work for the schools echo-sounder kit is excellent. The outreach component would reach the pupils at several local schools, and has the written support of both local teachers and the New Hampshire Sea Grant. The collaborations with industry, Sea Grant, and other agencies provides evidence that the project will have a wide spread and lasting impact and that it is perceived by many other scientists as an important problem and a good approach to the problem.