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EOS, TRANSACTIONS AMERICAN GEOPHYSICAL UNION, VOL. 87, NO. 22, doi:10.1029/2006EO220001, 2006

Shallow Seabed Methane Gas Could Pose Coastal Hazard

Angus I. Best

National Oceanography Centre, University of Southampton, UK


Michael D. Richardson

Naval Research Laboratory, Stennis Space Center, Mississippi, USA


Bernard P. Boudreau

Department of Oceanography, Dalhousie University, Halifax, Nova Scotia, Canada


Alan G. Judd

Wilderspool House, Stocksfield, UK


Ira Leifer

Marine Science Institute,Institute for Crustal Studies, University of California, Santa Barbara, California, USA


Anthony P. Lyons

Applied Research Laboratory, Pennsylvania State University, Pennsylvania, USA


Christopher S. Martens

Department of Marine Sciences, University of North Carolina, Chapel Hill, North Carolina, USA


Danial L. Orange

Department of Earth Sciences, University of California, Santa Cruz, California, USA
AOA Geophysics, Inc., Moss Landing, California, USA


Simon J. Wheeler

Department of Civil Engineering, University of Glasgow, UK


Abstract

Abnormally high levels of methane gas in seafloor sediments could pose a major hazard to coastal populations within the next 100 years through their impact on climate change and sea level rise. Marine scientists have known for many years that biogenic methane (CH4) is generated in shallow seabed sediments on continental margins, especially in rapidly deposited muddy sediments with high organic matter content (see Methane Flux Control in Ocean Margin Sediments (METROL) project in Mienert et al., [2004]). Gassy sediments are found in river deltas, estuaries, and harbors, but also in deeper waters on continental shelves and slopes. Human activities can accelerate natural seafloor gas generation by increasing the supply of sediments and organic matter from rivers through deforestation and intensive farming, and also by the disposal of human waste at sea. When this extra organic matter becomes buried to about one meter beneath the seabed, biogeochemical processes start to convert it to CH4 [Floodgate and Judd, 1992]. The impact of this extra CH4 could be left within the next 100 years, assuming a one-centimeter-per-year sediment accumulation rate.

Published 30 May 2006.

Index Terms: 1615 Global Change: Biogeochemical cycles, processes, and modeling (0412, 0414, 0793, 4805, 4912); 3002 Marine Geology and Geophysics: Continental shelf and slope processes (4219); 3004 Marine Geology and Geophysics: Gas and hydrate systems.

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Citation: Best, A. I., M. D. Richardson, B. P. Boudreau, A. G. Judd, I. Leifer, A. P. Lyons, C. S. Martens, D. L. Orange, and S. J. Wheeler (2006), Shallow Seabed Methane Gas Could Pose Coastal Hazard, Eos Trans. AGU, 87(22), doi:10.1029/2006EO220001.