A MODEL FOR ATMOSPHERIC CO2 OVER PHANEROZOIC TIME
A MODEL FOR ATMOSPHERIC CO2 OVER PHANEROZOIC TIME
复制标题
DOI：
10.2475/ajs.291.4.339
复制
发表时间：
1991-04-01
影响因子：
2.9
通讯作者：
BERNER, RA
中科院分区：
文献类型：
--
作者：
BERNER, RA
我们已经建立了一个新的模型来计算显生宙时期的大气CO2水平，该模型在数学上比BLAG模型简单得多，但在地质和生物学上却更为复杂。数学上的简化是通过只关注碳的循环，将所有碳酸盐矿物集中在一起，将海洋和大气结合成一个储存库，并将大气中的二氧化碳水平计算为一系列连续的海洋-大气稳定状态。Garrels和Lerman（1984）的同位素质量平衡模型进行了扩展，纳入了大陆面积、海拔和位置的变化以及陆地植物的演化对风化速率的影响，以及海底面积生成速率的变化以及深海与浅海台地碳酸盐沉积的相对重要性对全球脱气的影响。大气CO2水平是根据硅酸盐的风化反馈函数计算出来的，随着维管植物的出现和进化，硅酸盐随时间的变化而变化。结果表明，在过去的570年里，大气CO2水平呈现出明显的变化规律，在中生代和早古生代高，在二叠-石炭世和晚新生代低。灵敏度分析表明，在主要控制参数的合理范围内，CO2变化的这种定性趋势对这些参数所选的实际值相对不敏感。二氧化碳变化的原因是多重的，没有一个单一的地质或生物过程可以用来解释所有时间的所有二氧化碳变化。计算出的CO2随时间的变化趋势与对古气候的独立估计非常吻合。因此，长地质时间尺度上的古气候温室理论得到了本研究结果的支持。
A new model has been constructed for calculating the level of atmospheric CO2 over Phanerozoic time which is much simpler mathematically than the BLAG model, but more complex geologically and biologically. Mathematical simplification comes about by following the cycle of carbon only, lumping all carbonate minerals together, combining the ocean and atmosphere into one reservoir, and calculating atmospheric CO2 level as a series of successive ocean-atmosphere steady states. The isotope mass balance model of Garrels and Lerman (1984) is expanded to include the effect of changing area, elevation, and position of the continents as well as the evolution of land plants as they affect weathering rate, and changes in seafloor area generation rate and the relative importance of deep sea versus shallow platform carbonate deposition as they affect global degassing. Atmospheric CO2 level is calculated from a weathering feedback function for silicates which varies with time as vascular land plants arise and evolve.Results suggest that there has been a notable pattern of varying atmospheric CO2 level over the past 570 my with high levels during the Mesozoic and early Paleozoic and low levels during the Permo-Carboniferous and late Cenozoic. Sensitivity analysis shows that, within reasonable limits of the principal governing parameters, this qualitative trend of varying CO2 is relatively insensitive to the actual values chosen for these parameters. Causes of the CO2 variation are multiple, and no single geological or biological process can be called upon to explain all CO2 variation for all time.The calculated trend of CO2 over time agrees well with independent estimations of paleoclimates. Thus, the greenhouse theory of paleoclimate on a long geological time scale is supported by the results of the present study.