GAS EMISSIONS FROM MUD VOLCANOES: Significance to Global Climate Change

摘要

There are about 1,000 mud volcanoes on land and 5,500 offshore - mostly in deep water. Activity varies between gentle emissions and violent eruptions accompanied by the release of enormous volumes of gas - mainly (85%+) methane and carbon dioxide. Global gas emissions are provisionally estimated to exceed 27 billion cubic metres per year, of which more than 23 billion (15.8 Tg) is methane. More than 70% of this is from short-lived eruptions, about 30% of which ignite to produce flames tens or hundreds of metres high. The majority of the methane is emitted by submarine mud volcanoes, most in deep water. About 11.4 Tg per year is lost to the hydrosphere, but a tentatively estimated 3.6 Tg per year escapes to the atmosphere. So, mud volcanoes are significant sources of atmospheric methane, much of it 'fossil'. Contributions are thought to increase when sea level is low (in glaciations), providing negative feedback to global warming and working to limit climatic extremes.