Past extreme warming events linked to massive carbon release from thawing permafrost
Past extreme warming events linked to massive carbon release from thawing permafrost
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DOI：
10.1038/nature10929
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发表时间：
2012-04-05
期刊：
影响因子：
64.8
通讯作者：
Beerling, David J.
中科院分区：
文献类型：
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作者：
DeConto, Robert M.;Galeotti, Simone;Beerling, David J.
大约 55.5 至 5200 万年前，地球经历了一系列突然且极端的全球变暖事件（高温），并叠加了长期变暖趋势(1)。这些事件中的第一个也是最大的事件是古新世-始新世最热事件 (PETM)，其特点是大量碳输入、海洋酸化 (2) 以及全球温度在几千年内上升约 5 摄氏度 (3)。尽管人们对 PETM 提出了各种解释(4-6)，但仍然难以找到一个令人满意的模型来解释 PETM 和连续高温的碳释放的来源、强度和时间。在这里，我们使用来自意大利中部的新的天文校准旋回地层记录(7)来表明早始新世高温发生在高偏心率和高倾角组合的轨道上。相应的气候-生态系统-土壤模拟考虑了背景温室气体(8)浓度上升和轨道强迫，表明PETM和随后的高温的强度和时间可以通过轨道触发的环北极和南极陆地永久冻土中土壤有机碳的分解来解释。一旦在 PETM 之前达到长期变暖阈值，这个巨大的碳库就有可能反复向大气-海洋系统释放数千拍克（10（15）克）的碳。峰值变暖后永久冻土碳储量的补充可能有助于每次事件的快速恢复(9)，同时为下一次高温提供敏感的碳库(10)。随着PETM之后背景温度继续上升，永久冻土的面积范围稳步下降，导致可用碳库逐渐变小，并且在每个连续的轨道强迫最大值处的高温也逐渐变小。将地球轨道特性与永久冻土层土壤碳释放联系起来的机制提供了一个统一的模型来解释高温的显着特征。
Between about 55.5 and 52 million years ago, Earth experienced a series of sudden and extreme global warming events (hyperthermals) superimposed on a long-term warming trend(1). The first and largest of these events, the Palaeocene-Eocene Thermal Maximum (PETM), is characterized by a massive input of carbon, ocean acidification(2) and an increase in global temperature of about 5 degrees C within a few thousand years(3). Although various explanations for the PETM have been proposed(4-6), a satisfactory model that accounts for the source, magnitude and timing of carbon release at the PETM and successive hyperthermals remains elusive. Here we use a new astronomically calibrated cyclostratigraphic record from central Italy(7) to show that the Early Eocene hyperthermals occurred during orbits with a combination of high eccentricity and high obliquity. Corresponding climate-ecosystem-soil simulations accounting for rising concentrations of background greenhouse gases(8) and orbital forcing show that the magnitude and timing of the PETM and subsequent hyperthermals can be explained by the orbitally triggered decomposition of soil organic carbon in circum-Arctic and Antarctic terrestrial permafrost. This massive carbon reservoir had the potential to repeatedly release thousands of petagrams (10(15) grams) of carbon to the atmosphere-ocean system, once a long-term warming threshold had been reached just before the PETM. Replenishment of permafrost soil carbon stocks following peak warming probably contributed to the rapid recovery from each event(9), while providing a sensitive carbon reservoir for the next hyperthermal(10). As background temperatures continued to rise following the PETM, the areal extent of permafrost steadily declined, resulting in an incrementally smaller available carbon pool and smaller hyperthermals at each successive orbital forcing maximum. A mechanism linking Earth's orbital properties with release of soil carbon from permafrost provides a unifying model accounting for the salient features of the hyperthermals.