Abundant Early Palaeogene marine gas hydrates despite warm deep-ocean temperatures
Abundant Early Palaeogene marine gas hydrates despite warm deep-ocean temperatures
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DOI：
10.1038/ngeo1301
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发表时间：
2011-12
影响因子：
18.3
通讯作者：
G. Gu;G. Dickens;Gaurav Bhatnagar;F. Colwell;G. Hirasaki;Walter G Chapman
中科院分区：
文献类型：
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作者：
G. Gu;G. Dickens;Gaurav Bhatnagar;F. Colwell;G. Hirasaki;Walter G Chapman
5700万年前到5000万年前的全球变暖的突然时期-被称为古近纪早期高温事件-与大量的碳反复注入大气层有关。天然气水合物分解后从海底释放的甲烷常常被认为是一种来源。然而，事件发生前的海底温度至少比今天高4-7 °C，这将限制适合容纳天然气水合物的海底面积。因此，古近系天然气水合物储层可能不足以提供释放的碳的重要部分。在这里，我们使用数值模拟的天然气水合物积累在古近纪海底温度显示，近今天的价值的天然气水合物可能已经托管在古近纪。我们的模拟表明，在古近纪温暖的温度会增加到达海底的有机碳的数量以及甲烷生成的速度。我们发现，在合理的温度和压力条件下，天然气水合物的丰度在古近纪将类似或高于现在。我们的结论是，甲烷水合物可能是一个重要的碳源，在古近纪超热事件。
Abrupt periods of global warming between 57 and 50 million years ago—known as the Early Palaeogene hyperthermal events—were associated with the repeated injection of massive amounts of carbon into the atmosphere,,,. The release of methane from the sea floor following the dissociation of gas hydrates is often invoked as a source. However, seafloor temperatures before the events were at least 4–7 °C higher than today, which would have limited the area of sea floor suitable for hosting gas hydrates,. Palaeogene gas hydrate reservoirs may therefore not have been sufficient to provide a significant fraction of the carbon released. Here we use numerical simulations of gas hydrate accumulation at Palaeogene seafloor temperatures to show that near-present-day values of gas hydrates could have been hosted in the Palaeogene. Our simulations show that warmer temperatures during the Palaeogene would have enhanced the amount of organic carbon reaching the sea floor as well as the rate of methanogenesis. We find that under plausible temperature and pressure conditions, the abundance of gas hydrates would be similar or higher in the Palaeogene than at present. We conclude that methane hydrates could have been an important source of carbon during the Palaeogene hyperthermal events.