Methane Venting from Forearc Faults in the Puget Sound Estuary

从普吉特湾河口喷出的甲烷大陆边缘的浅海水域是向空气中排放甲烷的活跃区域。这些地区提供了导致现代气候变暖的温室效应的主要部分。最近的研究表明，来自沿海浅海的甲烷提供了空气中甲烷排放总量的一半，而甲烷排放反过来又会导致全球变暖。普吉特海湾是北美最大的内陆海，也是空气中甲烷的一大来源。从海底新发现的气泡羽流中产生的气体增加了普吉特海湾海水中的甲烷含量。这种来自海底的气体从海面逃逸到空气中，在那里成为温室气体。显示新发现的喷口中甲烷地下矿藏的位置是这项研究项目的主要目标。来自海底的甲烷气体量将使用一种名为遥控运载器(ROV)的机器人仪器进行测量。这个机器人设备将把测量仪器直接放置在甲烷泡沫流的路径上，以显示流动速度并从通风口捕获液体。来自该大学工程系中代表性不足的有色人种社区的五名学生将被邀请为船上的科学派对成员。这一经历将大大拓宽他们在海洋科学方面的教育经验。为了找到最近发现的涌入普吉特湾海水的甲烷气体的来源，该项目将仔细测量从海底流出甲烷气体的速率的变化。在六个月的时间里，来自海底喷口的气体和液体的变化将与可能导致流量变化的环境事件进行比较。可能导致喷口流量变化的事件包括异常的水潮、季节引起的温度变化、地震产生的波，以及附近陆地上异常大的降雨事件。该项目中的两次研究巡航将于2022年秋末和2023年春季进行，以观察喷口流量随温度和降雨量随季节变化而发生的变化。研究的船上部分将使用拖曳在海底附近的摄像系统来绘制喷口区域的细节。小型遥控运载器(ROV)也将使用专门建造的样品瓶捕获从海底喷口流出的气体和液体。然后，水下机器人将在海底放置仪器，观察六个月内气体流速的变化。这些捕获的流体样本将显示甲烷是来自地球深处，还是来自附近陆地的雨水径流。该研究项目的数据将通过发布在大学网站上向公众免费提供，并保存在联邦档案馆中。华盛顿大学工程系针对未被充分代表的有色人种学生项目的本科生将参加船上的海洋实地项目和实验室的数据处理过程。这种在海上和实验室的亲身体验将提高学生对海洋科学的认识。这一奖项反映了NSF的法定使命，并通过使用基金会的智力优势和更广泛的影响审查标准进行评估，被认为值得支持。

Methane Venting from the Puget Sound EstuaryShallow coastal waters found on the margins of continents are areas of active methane emissions to the air. These areas supply a major part of the greenhouse effect responsible for modern climate warming. Recent studies have shown that methane from shallow coastal waters supply half of all methane emissions to the air that in turn produce global warming. Puget Sound is the largest of these inland seas in North America and is a large source of methane to the air. Gas from newly-discovered bubble plumes from the seafloor increases the amount of methane in the Puget Sound seawater. This gas from the seafloor escapes to the air from the sea surface where it becomes a greenhouse gas. Showing the location of the sub-surface deposits of methane in the newly discovered vents is the primary goal of this research project. The amount of methane gas coming from the seafloor will be measured using a robotic instrument called a Remotely Operated Vehicle (ROV). This robotic device will place measuring instruments directly in the path of the methane bubble stream to show the flow speed and capture fluid from the vents. Five students from under-represented communities of color in the university’s Engineering Department will be invited as members of the science party on the ship. This experience will substantially broaden their education experience in marine sciences.To find the source of methane gas recently discovered venting into Puget Sound seawater, this project will carefully measure changes in the rate of methane gas flowing from the seafloor. The changes in gas and fluid coming from seafloor vents over a six month period will be compared to environmental events that could be causing the flow changes. Examples of events that could cause vent flow changes include unusual water tides, temperature changes due to seasons, passing waves from earthquakes, and unusually large rainfall events in the nearby land. The two research cruises in the program will occur in late Fall 2022 and in Spring of 2023 to see changes in vent flow as the temperature and rainfall vary with the seasons. The shipboard part of the research will use a camera system towed near the seafloor to map the details of the vent field. A small Remotely Operated Vehicle (ROV) will also capture gas and fluid that is flowing from the seafloor vents using specially constructed sample bottles. The ROV will then place instruments on the seafloor to see variations in the gas flow rate for a six-month period. These captured fluid samples will show whether the methane is coming from deep within the earth or if it is coming as runoff of rain from the nearby land. Data from the research program will be freely available to the public through publication on university websites and placed in the federal archives. University of Washington undergraduates from the Engineering Department’s program for under-represented students of color will take part in both ocean field programs on the ship and during the processing of the data in the laboratory. This firsthand experience at sea and in the laboratory will increase the student’s awareness of marine sciences.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.