Earth system model simulations show different feedback strengths of the terrestrial carbon cycle under glacial and interglacial conditions
Earth system model simulations show different feedback strengths of the terrestrial carbon cycle under glacial and interglacial conditions
复制标题
DOI：
10.5194/esd-9-413-2018
复制
发表时间：
2018-04-25
影响因子：
7.3
通讯作者：
Claussen, Martin
中科院分区：
文献类型：
--
作者：
Adloff, Markus;Reick, Christian H.;Claussen, Martin
在MPI地球系统模式的模拟中，我们研究了冰期和间冰期条件下陆地碳循环和大气CO2浓度之间的反馈。我们发现不同的敏感性陆地碳储量上升的CO2浓度在这两个设置。这一结果是通过比较陆地碳循环的瞬态响应快速和强烈的大气CO2浓度增加（约900 ppm）耦合气候碳循环模型相互比较项目（C4 MIP）型模拟从气候代表末次冰期最大（LGM）和前工业时代（PI）。在这种设置中，我们解开陆地贡献的反馈，从碳浓度的影响，通过增强光合生产力时，二氧化碳浓度增加，和碳气候效应，通过温室效应影响碳循环的地球化学作用。我们发现，碳浓度的影响是更大的LGM比PI条件下，因为光合生产力是更敏感的，从较低的，冰川CO2浓度和CO2施肥饱和后。这导致LGM实验中更大的生产率增加。关于碳-气候效应，这是PI实验，在该实验中，陆地碳对CO2上升下的变暖反应更敏感，因为在最初的较高温度下，热带植物生产力恶化得更厉害，热带外的碳被更有效地呼吸。因此，土地碳损失在PI比在LGM的情况下增加得更快。分离的碳气候和碳浓度的影响，我们发现，他们几乎是添加剂为我们的模型设置，即它们的协同作用是在全球碳变化的总和很小。总之，这两种效应导致陆地碳循环反馈的总体强度几乎是LGM实验中PI实验的两倍。对于PI，海洋和陆地对总反馈的贡献大小相似，而在LGM的情况下，陆地反馈占主导地位。
In simulations with the MPI Earth System Model, we study the feedback between the terrestrial carbon cycle and atmospheric CO2 concentrations under ice age and interglacial conditions. We find different sensitivities of terrestrial carbon storage to rising CO2 concentrations in the two settings. This result is obtained by comparing the transient response of the terrestrial carbon cycle to a fast and strong atmospheric CO2 concentration increase (roughly 900 ppm) in Coupled Climate Carbon Cycle Model Intercomparison Project (C4MIP)-type simulations starting from climates representing the Last Glacial Maximum (LGM) and pre-industrial times (PI). In this set-up we disentangle terrestrial contributions to the feedback from the carbon-concentration effect, acting biogeochemically via enhanced photosynthetic productivity when CO2 concentrations increase, and the carbonclimate effect, which affects the carbon cycle via greenhouse warming. We find that the carbon-concentration effect is larger under LGM than PI conditions because photosynthetic productivity is more sensitive when starting from the lower, glacial CO2 concentration and CO2 fertilization saturates later. This leads to a larger productivity increase in the LGM experiment. Concerning the carbon-climate effect, it is the PI experiment in which land carbon responds more sensitively to the warming under rising CO2 because at the already initially higher temperatures, tropical plant productivity deteriorates more strongly and extratropical carbon is respired more effectively. Consequently, land carbon losses increase faster in the PI than in the LGM case. Separating the carbon-climate and carbon-concentration effects, we find that they are almost additive for our model set-up; i.e. their synergy is small in the global sum of carbon changes. Together, the two effects result in an overall strength of the terrestrial carbon cycle feedback that is almost twice as large in the LGM experiment as in the PI experiment. For PI, ocean and land contributions to the total feedback are of similar size, while in the LGM case the terrestrial feedback is dominant.