Cenozoic global ice volume and temperature simulations over the past 40 million years

Variations in global ice volume and temperature over the Cenozoic era have been investigated with a set of one-dimensional (1-D) ice-sheet models. Simulations include three ice sheets representing glaciation in the Northern Hemisphere, i.e. in Eurasia, North America and Greenland, and two separate ice sheets for Antarctic glaciation. The continental mean Northern Hemisphere surface-air temperature has been derived through an inverse procedure from observed benthic d18O records. These data have yielded a mutually consistent and continuous record of temperature, global ice volume and benthic d18O over the past 35 Ma. The simple 1-D model shows good agreement with a comprehensive 3-D ice-sheet model for the past 3 Ma. On average, differences are only 1.0°C for temperature and 6.2 m for sea level. Most notably, over the 35 Ma period, the reconstructed ice volume–temperature sensitivity shows a transition from a climate controlled by Southern Hemisphere ice sheets to one controlled by Northern Hemisphere ice sheets. Although the transient behaviour is important, equilibrium experiments show that the relationship between temperature and sea level is linear and symmetric, providing limited evidence for hysteresis. Furthermore, the results show a good comparison with other simulations of Antarctic ice volume and observed sea level.本研究采用一套一维（1-D）冰盖模型，对新生代时期全球冰量与地表温度的演变特征展开了探究。模拟方案共包含五座冰盖：三座对应北半球冰川作用，分别覆盖欧亚大陆、北美大陆与格陵兰岛；另外两座独立冰盖则表征南极冰川作用。研究通过反演流程，由观测得到的底栖d¹⁸O记录重建了北半球大陆平均地表气温序列。该数据集构建了过去35百万年（Ma）间温度、全球冰量与底栖d¹⁸O的连续且自洽的演化记录。在过去3 Ma的时间尺度上，该简化一维模型与一套完备的三维（3-D）冰盖模型的模拟结果吻合度较高。平均而言，两者在温度模拟上的差值仅为1.0℃，海平面模拟差值仅为6.2米。尤为关键的是，在35 Ma的时间跨度内，重建得到的冰量-温度敏感性参数呈现出显著转变：气候调控主体由南半球冰盖逐渐切换为北半球冰盖。尽管瞬态演化过程至关重要，但平衡态实验结果表明，温度与海平面间的关系呈线性对称特征，仅能为滞后效应提供有限的佐证依据。此外，本研究结果与其他南极冰量模拟结果及观测海平面记录均展现出良好的一致性。