| Summary: | Methane is a potent greenhouse gas that is present in large amounts in frozen soils and marine sediments in the Arctic. In marine sediments, methane may be present either in permafrost or in gas hydrates. Warming of the Arctic may lead to the release of stored methane, leading to further warming and then to further methane releases in a reinforcing cycle. The East Siberian Sea, in the Arctic Ocean, is a large area with a great deal of undersea permafrost and, likely, stored methane. Recent work has suggested large sources of methane from parts of the East Siberian Sea, but the area needs to be mapped and studied in much greater detail before either the amount of methane stored there or the amount being released can be fully understood. In the summer of 2014, an international program called the Swedish-Russian-US Arctic Ocean Investigation of Climate-Cryosphere-Carbon Interactions (SWERUS-C3) will undertake a 90-day expedition to map, and study the carbon cycle in, the East Siberian Sea. The principal investigators of this proposal are leaders in ocean mapping and they have recently pioneered techniques for acoustic imaging of methane plumes released from the seafloor in the Gulf of Mexico. They have been invited by the leaders of the SWERUS-C3 team to participate in one leg of the expedition. They propose to use the multibeam sonar on board the ODEN to locate and characterize gas seeps in the water column and then apply a newly developed wideband transceiver to the split-beam echosounder on board the ODEN to constrain the size and fate of gas bubbles rising to the surface. Together, these acoustic observations will help the SWERUS-C3 team understand the flux of methane from the seafloor into the water column and potentially into the atmosphere. If successful, these techniques will allow the mapping of the gas flux in the Arctic over scales never before possible. This proposal requests support for the participation of the UNH team on this expedition and for post-cruise work-up of the data. The project will support a full time graduate student at UNH. A UNH undergraduate student will participate as well. The SWERUS-C3 program as a whole will support over 15 postdoctoral researchers and graduate students, and has a broad suite of outreach activities planned. The UNH Center for Coastal Ocean Mapping will also incorporate this work into ongoing outreach and education activities. Data were continuously sampled, digitized, and stored on a hard drive in Simrad EK80.raw datagrams (Approximately 1.2 Terabytes). Description of these datagrams can be found at: https://www.simrad.com/www/01/NOKBG0240.nsf/AllWeb/543880A07527F5D3C1257E52002246B6?OpenDocument Open source code and supported readers for these data can be found at: https://github.com/RobBlackwell/SimradRaw.jl to read in Julia and: https://bitbucket.org/echoanalysis/esp3/overview to use the ESP3 software package in MATLAB or to download the compiled version for non-MATLAB users on a Windows 64bits platform. At the time of publishing, the current version of the compiled release is v0.9.5, which can be downloaded as the attached file, “esp3_install_ver_0.9.5.msi”. Be aware that this software is under development so there may be more recent versions available.
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