在过去的6000万年中,大气中的二氧化碳度
1Department of Earth Sciences, University of Bristol, UK. Paul.Pearson@Bristol.ac.uk
Nature
|August 30, 2000
概括
大气中的二氧化碳 (CO2) 含量在地球早期的中生代时代较高,直到米奥森时代才不稳定地下降. 现代二氧化碳水平一直低于百万分之500部分 (ppm). 从那时起. 自那时以来.
科学领域:
- 古气候学 古气候学
- 地质化学 地质化学
- 海洋学 海洋学 海洋学
背景情况:
- 了解过去大气中的二氧化碳 (CO2) 度对于重建地球的气候和温度至关重要.
- 关于早期二氧化碳水平,其下降的时间和长期监管机制存在差异.
- 之前的估计表明,与今天相比,在早期代代 (大约6000万年前) 的二氧化碳水平更高.
研究的目的:
- 为了重建过去6000万年的大气二氧化碳度.
- 调查二氧化碳水平的下降,并确定潜在的控制因素.
- 为了提供更准确的二氧化碳波动和它们与气候的关系的时间表.
主要方法:
- 从古老的浮游生物中利用同位素的比率.
- 估计的表面层海水pH值来重建大气中的二氧化碳度.
- 分析了从古世末期到现在的地质时间表.
主要成果:
- 估计的二氧化碳度超过2000百万分之一 (ppm). 在古老纪晚期和古老纪早期 (60-52万年前).
- 在5500万至4000万年前观察到二氧化碳的不稳定下降,这可能与减少地质排气和增加碳埋葬有关.
- 发现的二氧化碳度保持在500ppm以下. 并且从米奥森早期 (2400万年前) 以后变得更加稳定,在冷却过程中短暂减少.
结论:
- 该研究提供了一个详细的重建Cenozoic大气二氧化碳水平.
- 减少火山排气和加强碳埋葬等机制可能推动了二氧化碳的长期下降.
- 迈奥森后的二氧化碳水平明显较低,更加稳定,这表明地球碳循环调节的转变.
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