大气中CH4的delta13C的冰记录跨越了年轻的Dryas-Preboreal过渡
Hinrich Schaefer1, Michael J Whiticar, Edward J Brook
1School of Earth and Ocean Sciences, University of Victoria, Post Office Box 3055, V8W 3P6, Canada. schaefeh@geo.oregonstate.edu
概括
大气中的甲碳同位素比率从格陵兰岛在年轻的干旱到前北极的过渡期间,表明自然甲排放较高或比以前假设的更强的沉降分成. 这表明在这个古老的气候转变期间存在复杂的甲循环.
科学领域:
- 古气候学 古气候学
- 大气化学 大气化学
- 同位素地球化学 同位素地球化学
背景情况:
- 年轻的干旱到前北极 (YD-PB) 的过渡标志着一个重要的气候转变.
- 大气中的甲 (CH4) 度及其同位素特征对于了解过去的气候动态至关重要.
- 以前的甲预算可能无法完全考虑自然的同位素变化.
研究的目的:
- 在YD-PB过渡期间重建大气中甲碳同位素比率 (delta13CH4).
- 在这个关键的气候时期调查甲的来源和沉积点.
- 将古代甲同位素数据与现代值和预算估计进行比较.
主要方法:
- 从冰核样本中分析甲碳同位素比率 (delta13CH4).
- 冰边缘在格陵兰西部进行冰芯钻探.
- 在已知的甲来源和沉积点的背景下解释同位素数据.
主要成果:
- 在YD-PB过渡的800年里,甲碳同位素比率 (delta13CH4) 在每毫米约为-46 保持相对不变.
- 这一值大约比现代大气层高出1毫升,而如果没有人为排放,则比预期高出5.5毫升.
- 在甲上升期间的恒定delta13CH4表明来自热带湿地或有氧植物CH4生产的贡献,而不是海洋酸盐.
结论:
- 同位素数据需要比传统假设更高的天然13C丰富的甲排放量或更强的沉降分化.
- 这些发现支持在YD-PB过渡期间甲排放的多来源场景.
- 在此期间,海洋酸甲释放不太可能成为重要来源.
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