Subsea ice‐bearing permafrost on the U.S. Beaufort Margin: 1. Minimum seaward extent defined from multichannel seismic reflection data

• Published in: Geochemistry, geophysics, geosystems : G3 Vol. 17; no. 11; pp. 4354 - 4365
• Main Authors: Brothers, Laura L., Herman, Bruce M., Hart, Patrick E., Ruppel, Carolyn D.
• Format: Journal Article
• Language: English
• Published: Washington John Wiley & Sons, Inc 01.11.2016
• Subjects: Arctic Ocean; Average velocity; Climate; Climate change; Continental shelves; Data; Degassing; Gas hydrates; Geographical distribution; Global warming; History; Hydrates; Ice; Isobaths; Modelling; multichannel seismic data; Permafrost; Permafrost distribution; Pleistocene; Reflection; Refraction; Saline intrusion; Saltwater intrusion; Seismic refraction; Shelf edge; Shorelines; subsea permafrost; Travel time; Velocity; Velocity distribution; Water depth; United States > US; PN, Arctic
• DOI: 10.1002/2016GC006584
• ISSN: 1525-2027

Subsea ice‐bearing permafrost (IBPF) and associated gas hydrate in the Arctic have been subject to a warming climate and saline intrusion since the last transgression at the end of the Pleistocene. The consequent degradation of IBPF is potentially associated with significant degassing of dissociating gas hydrate deposits. Previous studies interpreted the distribution of subsea permafrost on the U.S. Beaufort continental shelf based on geographically sparse data sets and modeling of expected thermal history. The most cited work projects subsea permafrost to the shelf edge (∼100 m isobath). This study uses a compilation of stacking velocity analyses from ∼100,000 line‐km of industry‐collected multichannel seismic reflection data acquired over 57,000 km2 of the U.S. Beaufort shelf to delineate continuous subsea IBPF. Gridded average velocities of the uppermost 750 ms two‐way travel time range from 1475 to 3110 m s−1. The monotonic, cross‐shore pattern in velocity distribution suggests that the seaward extent of continuous IBPF is within 37 km of the modern shoreline at water depths < 25 m. These interpretations corroborate recent Beaufort seismic refraction studies and provide the best, margin‐scale evidence that continuous subsea IBPF does not currently extend to the northern limits of the continental shelf. Key Points: Spatially extensive and dense velocity analyses are used to map subsea permafrost distribution on the U.S. Beaufort continental shelf This study provides margin‐scale evidence that continuous subsea IBPF does not currently extend to the edge of the continental shelf U.S. Beaufort subsea permafrost has degraded substantially and the shelf‐edge should be dismissed as the presumed extent of continuous IBPF