据研究人员介绍，研究使用CLIMBER-2地球系统模型模拟从上新世中期到现代前工业时代(3My-0My BP)，发现上新世-更新世冰川演化具有很强的路径依赖性，其驱动因素是火山二氧化碳排放的逐渐减少和基底冰相互作用的风化层去除。
研究利用在时间上向前和向后交替驱动模型，以探究路径的依赖性和滞后性。研究人员使用前工业化条件启动模型，并以时间反转的作用力驱动模型后向推动，火山除气后向时间(BIT)的增加并没有产生高CO2水平和上新世晚期相对无冰的条件，这在同一模型的前向时间(FIT)模拟中可以看到。这种行为似乎源于碳循环的非线性和初始状态依赖。
在FIT模拟中，从低振幅正弦倾角(~41 ky)和进动(~23 ky)驱动的冰期/间冰期旋回到高振幅~100 ky可能与偏心率相关的锯齿旋回(在1.25 My和0.75 My BP之间)的转变(中更新世转变或“MPT”)在BIT积分中消失，这取决于如何处理风化层去除过程的细节。为了再现MPT，需要向枯竭的风化层过渡和降低大气中的二氧化碳水平。
附：英文原文
Title: Path-dependence of the Plio–Pleistocene glacial/interglacial cycles
Author: Carrillo, Judit, Mann, Michael E., Larson, Christopher J., Christiansen, Shannon, Willeit, Matteo, Ganopolski, Andrey, Li, Xueke, Murphy, Jack G.
Issue&Volume: 2024-6-17
Abstract: We find strong path dependence in the evolution of the Plio–Pleistocene glaciations using CLIMBER-2 Earth System Model simulations from the mid-Pliocene to modern preindustrial (3 My-0 My BP) driven by a gradual decrease in volcanic carbon dioxide outgassing and regolith removal from basal ice interaction. Path dependence and hysteresis are investigated by alternatively driving the model forward and backward in time. Initiating the model with preindustrial conditions and driving the model backward using time-reversed forcings, the increase in volcanic outgassing back-in-time (BIT) does not generate the high CO2 levels and relatively ice-free conditions of the late Pliocene seen in forward-in-time (FIT) simulations of the same model. This behavior appears to originate from nonlinearities and initial state dependence in the carbon cycle. A transition from low-amplitude sinusoidal obliquity (~41 ky) and precession (~23 ky) driven glacial/interglacial cycles to high-amplitude ~100 ky likely eccentricity-related sawtooth cycles seen between 1.25 My and 0.75 My BP (the Mid-Pleistocene transition or “MPT”) in FIT simulations disappears in BIT integrations depending on the details of how the regolith removal process is treated. A transition toward depleted regolith and lowered atmospheric CO2 levels are both required to reproduce the MPT.
DOI: 10.1073/pnas.2322926121
Source: https://www.pnas.org/doi/abs/10.1073/pnas.2322926121