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1. (2014) Oregon Margin Southern Hydrate Summit 1 Seafloor (RS01SUM1)

   https://doi.org/10.58046/ooi-rs01sum1  

   NSF_Ocean_Observatories_Initiative (January 2014, US NSF Ocean Observatories Initiative)

   The Southern Hydrate Summit 1 Seafloor study site, situated on the continental slope off the coast of Oregon at a water depth of ~775 meters, hosts abundant deposits of gas hydrates (methane ice) that are buried beneath, and sometime exposed at, the seafloor. The deposits vent methane-rich fluids and bubbles that escape through seeps on the ocean bottom and can rise in plumes several hundred meters above the seafloor, also fueling dense communities of microbes and animals with chemosynthetic symbiotes. These seeps provide a unique opportunity to study ocean chemistry, quantify chemical fluxes from the seafloor, and observe the impacts of methane release on overlying seawater and biota. Methane is a powerful greenhouse gas and, therefore, quantifying the flux of methane from the seafloor into the hydrosphere is critical to understanding carbon-cycle dynamics and the impacts of global warming on methane release, particularly following seismic events. This Low-Power junction box (LJ01B) contains geophysical and near-seafloor water column instrumentation, and is attached to an electro-optical cable that provides significant power and 1 Gb two-way communications bandwidth. This junction box is also co-located with a Medium-Power junction box that collects a complementary suite of seafloor and water column measurements. 

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2. (2014) Oregon Margin Southern Hydrate Summit 2 Seafloor (RS01SUM2)

   https://doi.org/10.58046/ooi-rs01sum2  

   NSF_Ocean_Observatories_Initiative (January 2014, US NSF Ocean Observatories Initiative)

   The Southern Hydrate Summit 2 Seafloor study site, situated on the continental slope off the coast of Oregon at a water depth of ~775 meters, hosts abundant deposits of gas hydrates (methane ice) that are buried beneath, and sometime exposed at, the seafloor. The deposits vent methane-rich fluids and bubbles that escape through seeps on the ocean bottom and can rise in plumes several hundred meters above the seafloor, also fueling dense communities of microbes and animals with chemosynthetic symbiotes. These seeps provide a unique opportunity to study ocean chemistry, quantify chemical fluxes from the seafloor, and observe the impacts of methane release on overlying seawater and biota. Methane is a powerful greenhouse gas and, therefore, quantifying the flux of methane from the seafloor into the hydrosphere is critical to understanding carbon-cycle dynamics and the impacts of global warming on methane release, particularly following seismic events. This Medium-Power junction box (MJ01B) rests on the seafloor adjacent to a highly active methane seep called Einstein’s Grotto. Instrumentation at this site is designed to monitor chemistry of the seep, image the seep and associated biota in detail, and image the bubble plume as it rises several hundred meters above the seafloor. This junction box is attached to an electro-optical cable that provides significant power and 1 Gb two-way communications bandwidth, and is co-located with a Low-Power junction box that collects a complementary suite of geophysical and near-seafloor water column measurements. 

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3. Diverse gas composition controls the Moby-Dick gas hydrate system in the Gulf of Mexico

   https://doi.org/10.1130/G49310.1  

   Portnov, Alexey; Cook, A.E.; Vadakkepuliyambatta, S. (August 2021, Geology)

   Abstract In marine basins, gas hydrate systems are usually identified by a bottom simulating reflection (BSR) that parallels the seafloor and coincides with the base of the gas hydrate stability zone (GHSZ). We present a newly discovered gas hydrate system, Moby-Dick, located in the Ship Basin in the northern Gulf of Mexico. In the seismic data, we observe a channel-levee complex with a consistent phase reversal and a BSR extending over an area of ∼14.2 km2, strongly suggesting the presence of gas hydrate. In contrast to classical observations, the Moby-Dick BSR abnormally shoals 150 m toward the seafloor from west to east, which contradicts the northward-shallowing seafloor. We argue that the likely cause of the shoaling BSR is a gradually changing gas mix across the basin, with gas containing heavier hydrocarbons in the west transitioning to methane gas in the east. Our study indicates that such abnormal BSRs can be controlled by gradual changes in the gas mix influencing the shape of the GHSZ over kilometers on a basin scale. 

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4. Evolution of sediment temperature, pressure, phases distribution, carbon pools and seabed methane flux at the Arctic continental Shelves since the Last Glacial Maximum

   https://doi.org/10.5281/zenodo.8428754  

   You, Kehua (January 2023, Zenodo)

   This dataset are produced by a manuscript (Biodegradation of Ancient Organic Carbon Fuels Seabed Methane Emission at the Arctic Continental Shelves)  to be submitted to the Journal of Geophysical Research - Global Biogeochemical Cycles.  I The file "MethaneEmission_Permafrost" contains the predicted  temperature, pressure, pore water salinity, ice stable zone, methane hydrate stable zone, ice saturation, methane hydrate saturation, free methane gas saturation, labile organic carbon content, stable organic carbon content, and methanogenesis rate from seafloor to 1200 m depth from 18,000 years before present to 2,000 years after present for 8 different simulation scenarios.  The file "Seabed_Methane_Flux" contains the predicted seabed methane emission rate from 18,000 years before present to 2,000 years after present for 8 different simulation scenarios.  Detailed information about the model could be found in the paper Biodegradation of Ancient Organic Carbon Fuels Seabed Methane Emission at the Arctic Continental Shelves.    

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5. Physical Properties and Gas Hydrate at a Near-Seafloor Thrust Fault, Hikurangi Margin, New Zealand

   https://doi.org/10.1029/2020GL088474  

   Cook, A.E. (August 2020, Geophysical research letters)

   null (Ed.)

   The Pāpaku Fault Zone, drilled at International Ocean Discovery Program (IODP) Site U1518, is an active splay fault in the frontal accretionary wedge of the Hikurangi Margin. In logging-while-drilling data, the 33-m-thick fault zone exhibits mixed modes of deformation associated with a trend of downward decreasing density, P-wave velocity, and resistivity. Methane hydrate is observed from ~30 to 585 m below seafloor (mbsf), including within and surrounding the fault zone. Hydrate accumulations are vertically discontinuous and occur throughout the entire logged section at low to moderate saturation in silty and sandy centimeter-thick layers. We argue that the hydrate distribution implies that the methane is not sourced from fluid flow along the fault but instead by local diffusion. This, combined with geophysical observations and geochemical measurements from Site U1518, suggests that the fault is not a focused migration pathway for deeply sourced fluids and that the near-seafloor Pāpaku Fault Zone has little to no active fluid flow. 

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