Development and deployment of a novel deep-sea in situ bubble sampling instrument for understanding the fate of methane in the water column
Johnson, Andrew S.
MetadataShow full item record
Methane (CH4) is a potent greenhouse gas that is often found in a solid, hydrate clathrate form in marine sediments along continental margins and will often escape from the seafloor and rise through the water column as bubbles. The estimated marine methane hydrate inventory is over 600 times greater than the current atmospheric concentration so the fate of this ebullitive methane flux is of great interest. Traditional methods of measuring this flux such as acoustic imaging, optical sensors, and modeling suffer from limited information regarding the bubbles’ composition. Studies that attempt to constrain CH4 bubble composition suffer from low spatiotemporal resolution and adaptability. The current study presents the design, development and deployment of a novel, in situ bubble sampling system, the Bubble Delivery System (BDS), to quantify gas chemical composition in the water column. The BDS was deployed at the Cascadia Margin – a region well known for its active CH4 bubble seeps – where 95 samples were collected from McArthur Ridge, Hydrate Ridge, Heceta Deep and Heceta Shallow over the course of seven remotely operated vehicle dives. By combining this approach with the use of an underwater mass spectrometer, in situ analysis of these samples indicated that the bubbles contained between 84.6 to 100% CH4 and exhibited a high level of variability both spatially and temporally. Bubbles emitted from Heceta Deep exhibited anomalously elevated levels of carbon dioxide compared to the other sites.
Submitted in partial fulfillment of the requirements for the degree of Master of Science in Mechanical Engineering at the Massachusetts Institute of Technology and the Woods Hole Oceanographic Institution September 2019.
Suggested CitationThesis: Johnson, Andrew S., "Development and deployment of a novel deep-sea in situ bubble sampling instrument for understanding the fate of methane in the water column", 2019-09, DOI:10.1575/1912/24607, https://hdl.handle.net/1912/24607
Showing items related by title, author, creator and subject.
Vertical flux, ecology and dissolution of radiolaria in tropical oceans : implications for the silica cycle Takahashi, Kozo (Massachusetts Institute of Technology and Woods Hole Oceanographic Institution, 1981-11)Radiolarians which settle through the oceanic water column were recovered from three stations (western Tropical Atlantic-Station E, central Tropical Pacific-Pi and Panama Basin-PB) using PARLUX sediment traps in moored ...
Jaroslow, Gary E. (Massachusetts Institute of Technology and Woods Hole Oceanographic Institution, 1996-12)The objective of this Thesis was to interpret the structural development of slowspreading ridge segments by: 1) delineating the nature, magnitude, and relative importance of primary tectonic and volcanic processes that ...
Studies of the waters on the continental shelf, Cape Cod to Chesapeake Bay. I. The cycle of temperature Bigelow, Henry Bryant (Massachusetts Institute of Technology and Woods Hole Oceanographic Institution, 1933-12)When the U. S. Bureau of Fisheries, in cooperation with the Museum of Comparative Zoology, commenced the oceanographic survey of the Gulf of Maine in the summer of 1912 (Bigelow, 1925-1927), it was in the hope that this ...