Details

Autor(en) / Beteiligte

• Thomsen, Laurenz
• Barnes, Christopher
• Best, Mairi
• Chapman, Ross
• Pirenne, Benoît
• Thomson, Richard
• Vogt, Joachim

Titel

Ocean circulation promotes methane release from gas hydrate outcrops at the NEPTUNE Canada Barkley Canyon node

Ist Teil von

• Geophysical research letters, 2012-08, Vol.39 (16), p.n/a

Ort / Verlag

Washington, DC: Blackwell Publishing Ltd

Erscheinungsjahr

2012

Quelle

Wiley-Blackwell Journals

Beschreibungen/Notizen

• The NEPTUNE Canada cabled observatory network enables non‐destructive, controlled experiments and time‐series observations with mobile robots on gas hydrates and benthic community structure on a small plateau of about 1 km2 at a water depth of 870 m in Barkley Canyon, about 100 km offshore Vancouver Island, British Columbia. A mobile Internet operated vehicle was used as an instrument platform to monitor and study up to 2000 m2of sediment surface in real‐time. In 2010 the first mission of the robot was to investigate the importance of oscillatory deep ocean currents on methane release at continental margins. Previously, other experimental studies have indicated that methane release from gas hydrate outcrops is diffusion‐controlled and should be much higher than seepage from buried hydrate in semipermeable sediments. Our results show that periods of enhanced bottom currents associated with diurnal shelf waves, internal semidiurnal tides, and also wind‐generated near‐inertial motions can modulate methane seepage. Flow dependent destruction of gas hydrates within the hydrate stability field is possible from enhanced bottom currents when hydrates are not covered by either seafloor biota or sediments. The calculated seepage varied between 40–400 μmol CH4 m−2 s−1. This is 1–3 orders of magnitude higher than dissolution rates of buried hydrates through permeable sediments and well within the experimentally derived range for exposed gas hydrates under different hydrodynamic boundary conditions. We conclude that submarine canyons which display high hydrodynamic activity can become key areas of enhanced seepage as a result of emerging weather patterns due to climate change. Key Points Oscillatory currents modulate methane seepage Internet operated vehicles improve deep sea science Oscillatory currents and methane seepage must be further studied