Accession Number : ADP007358

Title :   A Review of Arctic Gas Hydrates as a Source of Methane in Global Change,

Corporate Author : GEOLOGICAL SURVEY MENLO PARK CA

Personal Author(s) : Kvenvolden, Keith A.

Report Date : MAR 1992

Pagination or Media Count : 6

Abstract : Atmospheric concentrations of methane are currently increasing at rates of about one percent per year, leading to a concern that methane, a greenhouse gas, will become an increasingly significant factor in global warming. One potential source of enormous volumes of methane is natural gas hydrates, which are solids composed of cages of water molecules that contain gas molecules, mainly methane. Gas hydrates are stable only within certain ranges of temperature and pressure; outside these ranges, the cages break down and the gas molecules escape. The Arctic is particularly well endowed with gas hydrates because conditions for their occurrence are met in three distinct regions: (1) offshore in sediments of the outer continental margin, at water depths between about 400 and 2800 m, where the base of the zone of gas hydrate stability ranges from about 300 to 700 m below the sea floor; (2) onshore in areas of continuous permafrost, where the zone of gas hydrate stability ranges in subsurface depth from about 200 to 1200 m; and (3) on the nearshore continental shelf, where relict permafrost has persisted since times of lower sea level when the present shelf was exposed to cold subaerial temperatures. Because gas hydrates occur close to the earth's surface in these three regions, they are affected by surficial changes in pressure and temperature, and thus destabilized gas hydrates may be sources of atmospheric methane.

Descriptors :   *ATMOSPHERICS, *METHANE, *ARCTIC REGIONS, DEPTH, GLOBAL, HYDRATES, MOLECULES, NATURAL GAS, OCEANS, OFFSHORE, PERMAFROST, PRESSURE, RATES, REGIONS, SEA LEVEL, SEDIMENTS, SOLIDS, STABILITY, SUBSURFACE, SURFACES, TEMPERATURE, VOLUME, WATER, SYMPOSIA, GREENHOUSE EFFECT.

Subject Categories : Geography
      Geology, Geochemistry and Mineralogy
      Meteorology

Distribution Statement : APPROVED FOR PUBLIC RELEASE