Simulation of climate, ice sheets and CO2 evolution during the last four glacial cycles with an Earth system model of intermediate complexity
Simulation of climate, ice sheets and CO2 evolution during the last four glacial cycles with an Earth system model of intermediate complexity
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DOI：
10.5194/cp-13-1695-2017
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发表时间：
2017-11-29
影响因子：
4.3
通讯作者：
Brovkin, Victor
中科院分区：
文献类型：
--
作者：
Ganopolski, Andrey;Brovkin, Victor
尽管在古气候重建和模拟过去的冰川周期的不同方面取得了重大进展，但将太阳辐射的区域和季节变化转化为长期和全球尺度的冰川-间冰期周期的机制仍然没有完全理解，特别是与CO2变化有关。在这里，使用中等复杂性的地球系统模型CLIMBER-2，我们进行了模拟的气候，冰盖和碳循环在过去的40万年的共同进化，使用轨道强迫作为唯一的外部强迫。该模型模拟的时间动态的CO2，全球冰量，和其他气候系统的特征与古气候重建。这些结果提供了强有力的支持的想法，长期和强烈不对称的晚第四纪冰川周期代表了一个直接的，但强烈的非线性响应的北方半球冰盖轨道强迫。这种反应被碳循环反馈强烈放大和全球化。使用不同配置的模型进行模拟，我们还分析了单个过程的作用和模型参数选择的敏感性。虽然模拟的冰川循环的许多功能是相当强大的，一些细节的CO2演变，特别是在冰川终止，是敏感的模型参数的选择。具体来说，我们发现两个主要制度的CO2变化在终止：在第一个，当大西洋纬向翻转环流（AMOC）的恢复只发生在终止结束时，一个明显的过冲CO2浓度发生在开始的间冰期和CO2几乎保持不变，在间冰期甚至下降到年底，类似Eemian CO2动态。然而，如果AMOC的恢复发生在冰期终止的中期，CO2浓度在间冰期继续上升，类似于全新世。我们还讨论了盐水排斥机制的CO2和碳同位素在大气和海洋在过去的冰期终止的潜在贡献。
In spite of significant progress in paleoclimate reconstructions and modelling of different aspects of the past glacial cycles, the mechanisms which transform regional and seasonal variations in solar insolation into long-term and global-scale glacial-interglacial cycles are still not fully understood-in particular, in relation to CO2 variability. Here using the Earth system model of intermediate complexity CLIMBER-2 we performed simulations of the coevolution of climate, ice sheets, and carbon cycle over the last 400 000 years using the orbital forcing as the only external forcing. The model simulates temporal dynamics of CO2, global ice volume, and other climate system characteristics in good agreement with paleoclimate reconstructions. These results provide strong support for the idea that long and strongly asymmetric glacial cycles of the late Quaternary represent a direct but strongly nonlinear response of the Northern Hemisphere ice sheets to orbital forcing. This response is strongly amplified and globalised by the carbon cycle feedbacks. Using simulations performed with the model in different configurations, we also analyse the role of individual processes and sensitivity to the choice of model parameters. While many features of simulated glacial cycles are rather robust, some details of CO2 evolution, especially during glacial terminations, are sensitive to the choice of model parameters. Specifically, we found two major regimes of CO2 changes during terminations: in the first one, when the recovery of the Atlantic meridional overturning circulation (AMOC) occurs only at the end of the termination, a pronounced overshoot in CO2 concentration occurs at the beginning of the interglacial and CO2 remains almost constant during the interglacial or even declines towards the end, resembling Eemian CO2 dynamics. However, if the recovery of the AMOC occurs in the middle of the glacial termination, CO2 concentration continues to rise during the interglacial, similar to the Holocene. We also discuss the potential contribution of the brine rejection mechanism for the CO2 and carbon isotopes in the atmosphere and the ocean during the past glacial termination.