冻土区甲烷排放研究进展

冻土区土牡表面和活动层土的ＣＨ_４排放和吸收表现出强烈的时空变化性。根据多年冻土中ＣＨ_４含量的模拟结果表明，全球尺度上，平均每米厚度多年冻土含有ＣＨ_４６５Ｔｇ。在未来的２００年间，多年冻土融化所导致的大气ＣＨ_４附加年源强变化于２～２５Ｔｇ。

METHANE EMISSIONS IN PERMAFROST REGIONS

 When global warming，the heat-moisture regimes of permafrost，ecosystems and land surface processes in cold regions will experience dramatic changes;consequently，biogeochemical cycles and gas exchange processes in these regions will undergo profound shifting. Strong spatial and temporal variability of methane emissions from permafrost surface and active layer soils have been observed，in which the CH₄ emission rates of wet tundra vary from-20 to 2400 mg/m². h with the average of 29-380 mg/m², h and that of moist and dry tundra range from-2. 1 to 2216 mg/m². h with the average of 0-85. 4 mg/m². h.The annual source strength of soil surface in global permafrost surface may exceeds 35 Tg.The emissions of CH₄ in cold regions are controlled by ecosystematic community types，soil moisture and temperature，and are also significantly influenced by wetland distribution，nutrient availability，pH and Eh，organic matter in soils and vascular piants，etc. Climatic warming may firstly thaw the shallow permafrost and that in the vicinity of the southern and lower limit of permafrost，resulting in the release of the sequestered CH₄ and organic materials in permafrost. The results of simulations based on the methane content in permafrost show that 1 m thick permafrost contain 65 Tg CH₄ in global scale;the additional methane source as the results of the release of the trapped methane due to shallow permafrost thawing is quite limited，and most of methane effluxes from permafrost layer will be oxidized and absorbed in the topmost layers and active layer，the amount of methane come into the atmosphere will be insignificant.  The clathrate methane under permafrost regions is esimated as about 540 Tg，which is vulnerable to sharp climatic and environmental changes. Onshore and offshore permafrost in the Arctic regions might have been warming and releasing methane due to the destabilization of clathrates for quite along period，
but the release at present and in the next century will be small，and its feedbacks to golbal climate might be minor.