Impact of CO 2 and climate on the Last Glacial Maximum vegetation: results from the ORCHIDEE/IPSL models
Impact of CO 2 and climate on the Last Glacial Maximum vegetation: results from the ORCHIDEE/IPSL models
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DOI：
10.5194/cp-7-557-2011
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发表时间：
2011-01
影响因子：
4.3
通讯作者：
M. Woillez;M. Kageyama;G. Krinner;N. Noblet-Ducoudré;N. Viovy;M. Mancip
中科院分区：
文献类型：
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作者：
M. Woillez;M. Kageyama;G. Krinner;N. Noblet-Ducoudré;N. Viovy;M. Mancip
抽象的。根据21年前最后一次冰川高峰期(LGM)的花粉数据重建植被，揭示了与现代冰川完全不同的地貌，特别是两个半球的森林面积大规模退化。与今天潜在的植被相比，必须考虑两个主要因素来解释这些变化：总体上更凉爽、更干燥的气候和更低水平的大气二氧化碳。为了评估气候和大气CO2变化对全球植被的相对影响，我们利用IPSL_CM4_v1大气-海洋环流模式的输出，利用全球动态植被模式Orchidee模拟了现代或冰川CO2水平下潜在的现代植被和冰川植被的光合作用。兰花正确地再现了冰川植被的广泛特征。我们的模拟结果支持这样的观点，即冰川二氧化碳的生理效应是解释冰期植被变化的关键因素。在我们的模拟中，低大气二氧化碳是热带森林退化的唯一驱动因素，并解释了温带和北方森林对冰川条件的一半反应。我们的研究表明，对CO2变化的敏感性取决于一个地区的背景气候，也取决于植被类型，在我们的模型中，针叶树比阔叶树更敏感。这种敏感度的差异导致了其余模拟森林中阔叶林类型的优势，这一点没有得到花粉数据的支持，但仍表明二氧化碳对冰川植被组合有潜在影响。它还改变了树木之间的竞争关系，使对二氧化碳的反应幅度取决于最初的植被状态。
Abstract. Vegetation reconstructions from pollen data for the Last Glacial Maximum (LGM), 21 ky ago, reveal lanscapes radically different from the modern ones, with, in particular, a massive regression of forested areas in both hemispheres. Two main factors have to be taken into account to explain these changes in comparison to today's potential vegetation: a generally cooler and drier climate and a lower level of atmospheric CO2. In order to assess the relative impact of climate and atmospheric CO2 changes on the global vegetation, we simulate the potential modern vegetation and the glacial vegetation with the dynamical global vegetation model ORCHIDEE, driven by outputs from the IPSL_CM4_v1 atmosphere-ocean general circulation model, under modern or glacial CO2 levels for photosynthesis. ORCHIDEE correctly reproduces the broad features of the glacial vegetation. Our modelling results support the view that the physiological effect of glacial CO2 is a key factor to explain vegetation changes during glacial times. In our simulations, the low atmospheric CO2 is the only driver of the tropical forests regression, and explains half of the response of temperate and boreal forests to glacial conditions. Our study shows that the sensitivity to CO2 changes depends on the background climate over a region, and also depends on the vegetation type, needleleaf trees being much more sensitive than broadleaf trees in our model. This difference of sensitivity leads to a dominance of broadleaf types in the remaining simulated forests, which is not supported by pollen data, but nonetheless suggests a potential impact of CO2 on the glacial vegetation assemblages. It also modifies the competitivity between the trees and makes the amplitude of the response to CO2 dependent on the initial vegetation state.