The East Siberian Arctic Shelf holds large amounts of inundated carbon and methane (CH₄). Holocene warming by overlying seawater, recently fortified by anthropogenic warming, has caused thawing of the underlying subsea permafrost. Despite extensive observations of elevated seawater CH₄ in the past decades, relative contributions from different subsea compartments such as early diagenesis, subsea permafrost, methane hydrates, and underlying thermogenic/ free gas to these methane releases remain elusive. Dissolved methane concentrations observed in the Laptev Sea ranged from 3 to 1,500 nM (median 151 nM; oversaturation by ∼3,800%). Methane stable isotopic composition showed strong vertical and horizontal gradients with source signatures for two seepage areas of δ¹³C-CH₄ = (−42.6 ± 0.5)/(−55.0 ± 0.5) ‰ and δD-CH₄ = (−136.8 ± 8.0)/(−158.1 ± 5.5) ‰, suggesting a thermogenic/natural gas source. Increasingly enriched δ¹³C-CH₄ and δD-CH₄ at distance from the seeps indicated methane oxidation. The Δ¹⁴C-CH₄ signal was strongly depleted (i.e., old) near the seeps (−993 ± 19/−1050 ± 89‰). Hence, all three isotope systems are consistent with methane release from an old, deep, and likely thermogenic pool to the outer Laptev Sea. This knowledge of what subsea sources are contributing to the observed methane release is a prerequisite to predictions on how these emissions will increase over coming decades and centuries.

东西伯利亚北极大陆架拥有大量淹没的碳和甲烷 (CH ₄ )。由上覆海水引起的全新世变暖，最近因人为变暖而加强，导致下面的海底永久冻土融化。尽管在过去几十年中对升高的海水 CH ₄进行了广泛的观察，但不同海底区域（例如早期成岩作用、海底永久冻土、甲烷水合物和潜在的热成因/游离气体）对这些甲烷释放的相对贡献仍然难以捉摸。在拉普捷夫海中观察到的溶解甲烷浓度范围为 3 到 1,500 nM（中值 151 nM；过饱和度约为 3,800%）。甲烷稳定同位素组成显示出强烈的垂直和水平梯度以及δ ^{13 的}两个渗流区域的源特征C-CH ₄ = (-42.6 ± 0.5)/(-55.0 ± 0.5) ‰ 和 δD-CH ₄ = (-136.8 ± 8.0)/(-158.1 ± 5.5) ‰，表明存在热成因/天然气源。离渗漏处越远越富集的 δ ¹³ C-CH ₄和 δD-CH ₄表明甲烷氧化。Δ ¹⁴ C-CH ₄信号在渗漏附近强烈消耗（即，旧）（-993 ± 19/-1050 ± 89‰）。因此，所有三个同位素系统都与从一个古老的、深的、可能是热成因池到外部拉普捷夫海的甲烷释放一致。了解哪些海底来源导致观察到的甲烷释放是预测未来几十年和几个世纪这些排放量将如何增加的先决条件。