The role of ecosystem-atmosphere interactions in simulated Amazonian precipitation decrease and forest dieback under global climate warming
The role of ecosystem-atmosphere interactions in simulated Amazonian precipitation decrease and forest dieback under global climate warming
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DOI：
10.1007/s00704-004-0050-y
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发表时间：
2004-06-01
影响因子：
3.4
通讯作者：
Jones, CD
中科院分区：
文献类型：
--
作者：
Betts, RA;Cox, PM;Jones, CD
利用HadCM3LC耦合气候-碳循环模型对模拟的降水减少和森林枯死所涉及的各种强迫和反馈进行了研究。研究发现，大气CO2的上升通过气孔关闭的生理强迫对降水减少贡献了20%，当不考虑气孔关闭而只考虑CO2的辐射强迫时，降水减少贡献了80%。森林枯死对降水减少有两个正反馈；通过森林覆盖减少抑制当地蒸发水循环的生物地球物理反馈，以及通过二氧化碳释放加速全球变暖的生物地球化学反馈。生物地球物理反馈使降水减少率提高了20%，森林枯死树的碳循环反馈使降水减少率提高了5%。这一分析有助于解释为什么HadCM3LC模拟的亚马逊降水减少比其他GCMs模拟的更极端；在完全耦合的气候-碳循环模拟中，亚马逊地区大约一半的降水减少可归因于生理强迫、生物地球物理和全球碳循环反馈的组合，而这些通常未包括在其他GCM对未来气候变化的模拟中。分析还显示了区域尺度的气候和生态系统变化对全球二氧化碳和气候变化预估不确定性的潜在贡献。此外，反馈的重要性表明，人为引起的森林对气候变化脆弱性的增加可能对区域和全球尺度的气候敏感性产生影响。
A suite of simulations with the HadCM3LC coupled climate-carbon cycle model is used to examine the various forcings and feedbacks involved in the simulated precipitation decrease and forest dieback. Rising atmospheric CO2 is found to contribute 20% to the precipitation reduction through the physiological forcing of stomatal closure, with 80% of the reduction being seen when stomatal closure was excluded and only radiative forcing by CO2 was included. The forest dieback exerts two positive feedbacks on the precipitation reduction; a biogeophysical feedback through reduced forest cover suppressing local evaporative water recycling, and a biogeochemical feedback through the release of CO2 contributing to an accelerated global warming. The precipitation reduction is enhanced by 20% by the biogeophysical feedback, and 5% by the carbon cycle feedback from the forest dieback. This analysis helps to explain why the Amazonian precipitation reduction simulated by HadCM3LC is more extreme than that simulated in other GCMs; in the fully-coupled, climate-carbon cycle simulation, approximately half of the precipitation reduction in Amazonia is attributable to a combination of physiological forcing and biogeophysical and global carbon cycle feedbacks, which are generally not included in other GCM simulations of future climate change. The analysis also demonstrates the potential contribution of regional-scale climate and ecosystem change to uncertainties in global CO2 and climate change projections. Moreover, the importance of feedbacks suggests that a human-induced increase in forest vulnerability to climate change may have implications for regional and global scale climate sensitivity.