School of Geosciences, University of Louisiana at Lafayette, Lafayette, LA, 70503, USA.
Institute of Geosciences, Johannes Gutenberg University Mainz, D-55128, Mainz, Germany.
Sci Rep. 2020 Feb 13;10(1):2562. doi: 10.1038/s41598-020-59431-3.
Seafloor methane seepage is a significant source of carbon in the marine environment. The processes and temporal patterns of seafloor methane seepage over multi-million-year time scales are still poorly understood. The microbial oxidation of methane can store carbon in sediments through precipitation of carbonate minerals, thus providing a record of past methane emission. In this study, we compiled data on methane-derived carbonates to build a proxy time series of methane emission over the last 150 My and statistically compared it with the main hypothesised geological controllers of methane emission. We quantitatively demonstrate that variations in sea level and organic carbon burial are the dominant controls on methane leakage since the Early Cretaceous. Sea level controls methane seepage variations by imposing smooth trends on timescales in the order of tens of My. Organic carbon burial is affected by the same cyclicities, and instantaneously controls methane release because of the geologically rapid generation of biogenic methane. Both the identified fundamental (26-27 My) and higher (12 My) cyclicities relate to global phenomena. Temporal correlation analysis supports the evidence that modern expansion of hypoxic areas and its effect on organic carbon burial may lead to higher seawater methane concentrations over the coming centuries.
海底甲烷渗漏是海洋环境中碳的重要来源。然而，对于数百万年时间尺度上的海底甲烷渗漏过程和时间模式，我们仍知之甚少。通过碳酸盐矿物的沉淀，甲烷的微生物氧化可以将碳储存在沉积物中，从而为过去甲烷排放提供记录。在本研究中，我们汇编了有关甲烷衍生碳酸盐的数据，构建了过去 1.5 亿年来甲烷排放的代理时间序列，并对其与甲烷排放的主要假设地质控制因素进行了统计比较。我们定量证明，自白垩纪早期以来，海平面变化和有机碳埋藏是控制甲烷泄漏的主要因素。海平面通过在数十万年的时间尺度上施加平滑趋势来控制甲烷渗漏的变化。有机碳埋藏受到相同周期性的影响，并且由于生物成因甲烷的地质快速生成，瞬间控制着甲烷的释放。已识别的基本（26-27 万年）和更高（12 万年）周期性都与全球现象有关。时间相关分析支持这样的证据，即缺氧区的现代扩张及其对有机碳埋藏的影响可能导致未来几个世纪海水中甲烷浓度升高。
