JCR 269A: Arctic hydrate dissociation as a consequence of climate change: determining the vulnerable methane reservoir and gas escape mechanisms

Follow-up to IPY cruise JR211

Tim Minshull tmin@noc.soton.ac.uk,National Oceanography Centre Southampton

JCR 269A Research ObjectivesHow much gas might be released as the Arctic warms, and how quickly and by what routes will it be released?

“Steady state” dissociation “Disturbed state” dissociation

? Methane Flux

? Atmospheric Venting

? Gas Volume

? Gas Release Mechanism

? Hydrate Inventory

JCR 269A Research Objectives1. Define the structural and sedimentary architecture of sites of gas

venting at the landward limit of hydrate stability and at a pockmark in deeper water where gas is being released.

2. Determine the migration pathways for free gas.

3. Determine the sub-seabed distribution and amounts of hydrate and free gas (mainly during follow-up cruise in 2012).

The West Svalbard marginThe West Svalbard shelf and slope: • is bathed by a northward flowing filament of the North

Atlantic Current which is a crucial “barometer” of global ocean warming,

• is an area of known methane venting with over 250 individual gas bubble plumes ascending through the water-column (with the pre-dominant majority located at the immediate landward edge of the gas hydrate stability zone at ~396 m water depth),

• is relatively easily accessible with frequent visits of Norwegian, German, and UK vessels for sustained observing programmes.

JCR269A Cruise Objectives• Acquisition of a series of very-high-resolution seismic

reflection profiles using Ifremer’s SYSIF deep-towed Chirp profiler, at a site on the shelf and at a deep-water pockmark site

• Determining seismic velocities close to the seafloor by recording the SYSIF signal on ocean bottom seismometers

• Acquisition of complementary high-resolution seismic reflection profiles using Ifremer’s mini-GI gun and the University of Southampton’s high-resolution multichannel streamer

• Testing of the Southampton DASI electromagnetic source and recording of this source on seabed instruments

JCR269A Cruise ScheduleTentative schedule is:• Day 1- depart Longyearbyen• Days 1 - 3 – SYSIF profiling in methane plume area, including

deployment and recovery of OBSs• Day 4 - deployment/recovery of seafloor electromagnetic equipment and

test deployment of DASI • Days 5 – 7 – OBS deployment, SYSIF profiling and OBS recovery in

Vestnesa Ridge area• Days 7 – 9 – profiling with mini-GI gun with multichannel streamer in both

areas and additional SYSIF profiling in methane plume area• Day 10 – depart for UK