Blar i forfatter "Portnov, Alexey"

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    • Distinct methane-dependent biogeochemical states in Arctic seafloor gas hydrate mounds 

      Klasek, Scott A.; Hong, Wei-Li; Torres, Marta E.; Ross, Stella; Hostetler, Katelyn; Portnov, Alexey; Gründger, Friederike; Colwell, Frederick S. (Journal article; Tidsskriftartikkel; Peer reviewed, 2021-11-02)
      Archaea mediating anaerobic methane oxidation are key in preventing methane produced in marine sediments from reaching the hydrosphere; however, a complete understanding of how microbial communities in natural settings respond to changes in the flux of methane remains largely uncharacterized. We investigate microbial communities in gas hydrate-bearing seafloor mounds at Storfjordrenna, offshore ...

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

      Portnov, Alexey; Cook, A.E.; Vadakkepuliyambatta, Sunil (Journal article; Tidsskriftartikkel; Peer reviewed, 2021-08-12)
      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 ...

    • Offshore permafrost decay and massive seabed methane escape in water depths >20 m at the South Kara Sea shelf 

      Portnov, Alexey; Mienert, Jurgen; Cherkashov, Georgy; Rekant, Pavel; Semenov, Peter; Serov, Pavel; Vanshtein, Boris; Smith, Andrew James (Journal article; Tidsskriftartikkel; Peer reviewed, 2013-07-14)
      Since the Last Glacial Maximum (~19 ka), coastal inundation from sea-level rise has been thawing thick subsea permafrost across the Arctic. Although subsea permafrost has been mapped on several Arctic continental shelves, permafrost distribution in the South Kara Sea and the extent to which it is acting as an impermeable seal to seabed methane escape remains poorly understood. Here we use >1300 km ...

    • Widespread subseafloor gas hydrate in the Barents Sea and Norwegian Margin 

      Cook, A.E.; Portnov, Alexey; Heber, R.C.; Vadakkepuliyambatta, Sunil; Bünz, Stefan (Journal article; Tidsskriftartikkel; Peer reviewed, 2023-02-01)
      The distribution and concentration of subseafloor natural gas hydrate across margins is not well understood, because these systems are challenging to image and quantify remotely. Furthermore, it is unknown if shallow hydrate systems are linked to deeper oil and gas reservoirs. Herein, we analyze petroleum industry well logs with data in the gas hydrate stability zone and find that low concentrations ...