英国纽卡斯尔大学 Davies, Richard J. 团队的一项最新研究报道了甲烷从水合物稳定带底部的远距离迁移和排放。2023年12月6日出版的《自然—地球科学》杂志发表了这项成果。
团队研究人员使用三维(3D)地震图像显示，在Mauritanian边缘，甲烷迁移了到水合物稳定带底部以下至少40千米处，并通过陆架断裂处的23个凹痕排出，这可能发生在较温暖的第四纪间冰期。研究证明，在适当的条件下，在深水远端水合物中结合的96.5 %的甲烷中的一部分可以到达海底并在海洋水合物的陆地界限之外排放到海洋中。因此，在估计全球变暖期间由气候变化引起的甲烷释放时，应该考虑这个储库。
研究人员表示，海洋甲烷水合物是一种冰状物质，在水深大于约450-700米的海洋大陆边缘沉积物中稳定存在。由于水合物融化而释放的甲烷释放被认为是过去全球碳循环扰动的一种机制，并可能加剧正在发生的人为气候变化。在大陆边缘附近海洋水合物向陆地边界的底部水温升高，促使甲烷排放到海洋中，在这些地方，脆弱的水合物存在于海床上或海床以下。然而，该环境仅占全球水合物储层的 3.5 %。深层水中的水合物产生的甲烷进入大气的可能性被认为可以忽略不计。
附：英文原文
Title: Long-distance migration and venting of methane from the base of the hydrate stability zone
Author: Davies, Richard J., Yang, Jinxiu, Ireland, Mark T., Berndt, Christian, Maqueda, Miguel ngel Morales, Huuse, Mads
Issue&Volume: 2023-12-06
Abstract: Marine methane hydrate is an ice-like substance that is stable in sediment around marine continental margins where water depths are greater than ~450–700m. The release of methane due to melting of hydrates is considered to be a mechanism for past global carbon-cycle perturbations and could exacerbate ongoing anthropogenic climate change. Increases in bottom-water temperature at the landward limit of marine hydrate around continental margins, where vulnerable hydrate exists at or below the seabed, cause methane to vent into the ocean. However, this setting represents only ~3.5% of the global hydrate reservoir. The potential for methane from hydrate in deeper water to reach the atmosphere was considered negligible. Here we use three-dimensional (3D) seismic imagery to show that, on the Mauritanian margin, methane migrated at least 40km below the base of the hydrate stability zone and vented through 23 pockmarks at the shelf break, probably during warmer Quaternary interglacials. We demonstrate that, under suitable circumstances, some of the 96.5% of methane bound in deeper water distal hydrates can reach the seafloor and vent into the ocean beyond the landward limit of marine hydrate. This reservoir should therefore be considered for estimating climate change-induced methane release during a warming world.
DOI: 10.1038/s41561-023-01333-w
Source: https://www.nature.com/articles/s41561-023-01333-w