"Offshore permafrost decay and massive seabed methane escape in water depths >20 m at the South Kara Sea shelf,"by Alexey Portnov et al., GRL (2013) in press; doi: 10.1002/grl.50735

Geophysical Research Letters, (2013) in press; doi: 10.1002/grl.50735

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

1. Alexey Portnov^*, 
2. Andrew J. Smith,
3. Jürgen Mienert, 
4. Georgy Cherkashov,
5. Pavel Rekant, 
6. Peter Semenov, 
7. Pavel Serov and
8. Boris Vanshtein

Abstract

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 of high-resolution seismic (HRS) data to map hydroacoustic anomalies, interpreted to record seabed gas release, on the West Yamal shelf. Gas flares are widespread over an area of at least 7,500 km² in water depths >20 m. We propose that continuous subsea permafrost extends to water depths of ~20 m offshore and creates a seal through which gas cannot migrate. This Arctic shelf region where seafloor gas release is widespread suggests that permafrost has degraded more significantly than previously thought.

http://onlinelibrary.wiley.com/doi/10.1002/grl.50735/abstract