Holocene carbon cycle dynamics, links to model files

We are investigating the late Holocene rise in CO2 by performing four experiments with the climate-carbon-cycle model CLIMBER2-LPJ. Apart from the deep sea sediments, important carbon cycle processes considered are carbon uptake or release by the vegetation, carbon uptake by peatlands, and CO 2 release due to shallow water sedimentation of CaCO3. Ice core data of atmospheric CO2 between 8 ka BP and preindustrial climate can only be reproduced if CO2 outgassing due to shallow water sedimentation of CaCO3 is considered. In this case the model displays an increase of nearly 20 ppmv CO2 between 8 ka BP and present day. Model configurations that do not contain this forcing show a slight decrease in atmospheric CO2. We can therefore explain the late Holocene rise in CO2 by invoking natural forcing factors only, and anthropogenic forcing is not required to understand preindustrial CO2 dynamics.

本研究借助气候-碳循环模型CLIMBER2-LPJ开展四组模拟实验，探究全新世晚期大气二氧化碳（CO₂）浓度上升的成因。除深海沉积物过程外，本研究考量的关键碳循环过程包括植被的碳吸收与释放、泥炭地的碳固存，以及碳酸钙（CaCO₃）浅水环境沉积作用引发的二氧化碳脱气。若未考虑碳酸钙浅水环境沉积导致的二氧化碳脱气过程，则无法复现距今8 ka BP（即8000年前）至工业革命前的冰芯大气二氧化碳记录。在此模型配置下，可模拟出距今8 ka BP至今大气二氧化碳浓度上升近20 ppmv（体积百万分比）的结果。未纳入该强迫因子的模型配置，则会输出大气二氧化碳浓度小幅下降的模拟结果。因此，仅依靠自然强迫因子即可解释全新世晚期大气二氧化碳浓度上升的现象，阐释工业革命前的大气二氧化碳动态变化无需引入人为强迫因子。