Seasonal Dynamics of Methane and Carbon Dioxide Evasion From an Open System Pingo: Lagoon Pingo, Svalbard
Seasonal Dynamics of Methane and Carbon Dioxide Evasion From an Open System Pingo: Lagoon Pingo, Svalbard
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DOI：
10.3389/feart.2019.00030
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发表时间：
2019-02-27
影响因子：
2.9
通讯作者：
Turchyn, Alexandra, V
中科院分区：
文献类型：
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作者：
Hodson, Andrew Jonathan;Nowak, Aga;Turchyn, Alexandra, V
与释放的甲烷和二氧化碳从亚永久冻土地下水的过程被认为是通过一个为期一年的监测调查在西斯匹次卑尔根岛的陆地渗漏网站。该地点是一个开放系统的冰丘，被认为与过去10，000年来当地冰盖丧失后海岸线显著均衡恢复引起的前海底凹坑隆起有关。我们发现，当地显着的排放量的甲烷和（较少）二氧化碳的大气中的结果，从渗漏< 1 L s（-1），全年发生。水文和气象条件强有力地调节排放，导致在冬季冰破裂事件后富气流体的周期性爆发，以及在初夏被融水显著稀释的流体。在100天的夏季形成的池塘中，（45.6 +/- 10.0 gCH（4）-Cm（-2）和768 +/- 211 gCO（2）-Cm（-2））约占年总排放量（223 gCH（4）-Cm（-2）a（-1）和2，040 gCO（2）-Cm（-2）a（-1））的20%至40%。季节性的最大溶解甲烷浓度（高达14.5毫克L-1甲烷）的流体中观察到的冬季冰层下积累。然而，季节性最大溶解CO2水平（高达233毫克L-1）发生在夏末。冬季样品的δ C-13-CH 4组成之间的差异[平均58.2 +/- 8.01%（s.d.）]和夏末样品[平均66.9 ± 5.75%（s.d.）]表明在冬季冰盖下临时储存期间发生轻微氧化，尽管甲烷来源的季节性变化也可能是原因。然而，这种同位素组成强烈表明，主要是生物甲烷生产的海洋沉积物，位于薄的沿海永冻层。因此，对于了解冻土景观的季节性甲烷排放量，应仔细监测冻土下地下水渗漏的甲烷排放小热点。
The processes associated with the release of CH4 and CO2 from sub-permafrost groundwaters are considered through a year-long monitoring investigation at a terrestrial seepage site in West Spitsbergen. The site is an open system pingo thought to be associated with the uplift of a former sea-floor pockmark in response to marked isostatic recovery of the coastline following local ice sheet loss over the last 10,000 years. We find that locally significant emissions of CH4 and (less so) CO2 to the atmosphere result from a seepage < 1 L s(-1) that occurs all year. Hydrological and meteorological conditions strongly regulate the emissions, resulting in periodic outbursts of gas-rich fluids following ice fracture events in winter, and significant dilution of the fluids in early summer by meltwater. Evasion of both gases from a pond that forms during the 100 days summer (45.6 +/- 10.0 gCH(4)-C m(-2) and 768 +/- 211 gCO(2)-C m(-2)) constitute between roughly 20 and 40% of the total annual emissions (223 gCH(4)-C m(-2) a(-1) and 2,040 gCO(2)-C m(-2) a(-1)). Seasonal maximum dissolved CH4 concentrations (up to 14.5 mg L-1 CH4) are observed in the fluids that accumulate beneath the winter ice layer. However, seasonal maximum dissolved CO2 levels (up to 233 mg L-1) occur during late summer. Differences between the delta C-13-CH4 composition of the winter samples [average 58.2 +/- 8.01% (s.d.)] and the late summer samples [average 66.9 +/- 5.75% (s.d.)] suggest minor oxidation during temporary storage beneath the winter ice lid, although a seasonal change in the methane source could also be responsible. However, this isotopic composition is strongly indicative of predominantly biogenic methane production in the marine sediments that lie beneath the thin coastal permafrost layer. Small hotpots of methane emission from sub-permafrost groundwater seepages therefore deserve careful monitoring for an understanding of seasonal methane emissions from permafrost landscapes.