近日，中国科学院广州地球化学研究所张一歌团队报道了古新世-始新世极热期间，有氧甲烷氧化放大了北极的二氧化碳排放。2025年9月25日出版的《自然—地球科学》杂志发表了这项成果。
在北冰洋，极地放大推动的变暖速度是全球平均速度的两到三倍，而这种升温和相关的变冷预计将加速甲烷循环，影响区域和全球的碳循环。然而，他们对更温暖、更新鲜的北极甲烷循环的理解受到短期观测记录的限制。
研究组提出了古新世-始新世热极大期(PETM; ~56百万年前)，通过一种hopanoid化合物hop-17（21）-ene的出现而被鉴定出来，该化合物具有细菌甲烷煌斑岩的独特同位素特征。早新生代整体低硫酸盐海洋上的强化水文循环限制了沉积硫酸盐的有效性，抑制了硫酸盐依赖的厌氧甲烷氧化，促进了水柱中的好氧甲烷氧化，这与地质证据和沉积成岩模型结果一致。
与产生碱度的厌氧氧化不同，好氧甲烷氧化消耗氧气并产生二氧化碳。他们基于生物标志物的CO2重建表明，北冰洋成为一个净CO2存在，特别是在恢复阶段，这导致了PETM期间碳输入延长、温度上升和海洋酸化。这些发现强调了未来气候变化对北极碳循环的潜在重大扰动。
附：英文原文
Title: Arctic CO2 emissions amplified by aerobic methane oxidation during the Palaeocene–Eocene Thermal Maximum
Author: Kim, Bumsoo, Zhang, Yi Ge, Zeebe, Richard E., Shen, Jiaheng
Issue&Volume: 2025-09-25
Abstract: In the Arctic Ocean, polar amplification drives warming rates that are two to three times the global average, and this enhanced warming and the associated freshening are expected to accelerate methane cycling, impacting regional and global carbon cycling. However, our understanding of methane cycling in a warmer and fresher Arctic is limited by short observational records. Here we present biomarker evidence for prevalent aerobic methanotrophy in the Arctic Ocean during the Palaeocene–Eocene Thermal Maximum (PETM; ~56million years ago), identified through the occurrence of a hopanoid compound, hop-17(21)-ene, with a distinct isotopic signature characteristic of bacterial methanotrophy. During the PETM, intensified hydrological cycling atop an overall low-sulfate ocean of the early Cenozoic limited sedimentary sulfate availability, suppressing sulfate-dependent anaerobic methane oxidation and facilitating aerobic methane oxidation in the water column, consistent with our geological evidence and sediment diagenesis model results. Unlike anaerobic oxidation, which generates alkalinity, aerobic methane oxidation consumes oxygen and produces CO2. Our biomarker-based CO2 reconstructions indicate that the Arctic Ocean became a net CO2 source, particularly during the recovery stage, contributing to prolonged carbon input, temperature rise and ocean acidification during the PETM. These findings highlight potential major perturbations to Arctic carbon cycling under future climate change.
DOI: 10.1038/s41561-025-01784-3
Source: https://www.nature.com/articles/s41561-025-01784-3