In response to warming climate, methane can be released to Arctic Ocean sediment and waters from thawing subsea permafrost and decomposing methane hydrates. However, it is unknown whether methane derived from this sediment storehouse of frozen ancient carbon reaches the atmosphere. We quantified the fraction of methane derived from ancient sources in shelf waters of the U.S. Beaufort Sea, a region that has both permafrost and methane hydrates and is experiencing significant warming. Although the radiocarbon-methane analyses indicate that ancient carbon is being mobilized and emitted as methane into shelf bottom waters, surprisingly, we find that methane in surface waters is principally derived from modern-aged carbon. We report that at and beyond approximately the 30-m isobath, ancient sources that dominate in deep waters contribute, at most, 10 ± 3% of the surface water methane. These results suggest that even if there is a heightened liberation of ancient carbon-sourced methane as climate change proceeds, oceanic oxidation and dispersion processes can strongly limit its emission to the atmosphere.

中文翻译：

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古代甲烷对美国波弗特海陆架表层水的贡献有限。


为了应对气候变暖，海底永久冻土层融化和甲烷水合物分解，甲烷可能会释放到北冰洋沉积物和水域中。然而，目前尚不清楚从这个古老的冰冻碳沉积库中产生的甲烷是否会到达大气中。我们量化了美国波弗特海陆架水域中古代来源的甲烷比例，该地区既有永久冻土层又有甲烷水合物，并且正在经历严重的变暖。尽管放射性碳-甲烷分析表明古代碳正在被动员并以甲烷形式排放到陆架底部水域，但令人惊讶的是，我们发现地表水中的甲烷主要来自现代碳。我们报告说，在大约 30 米等深线及以上，深水中占主导地位的古代来源最多贡献了地表水甲烷的 10 ± 3%。这些结果表明，即使随着气候变化的进行，古代碳源甲烷的释放量增加，海洋氧化和扩散过程也可以强烈限制其向大气的排放。