Multiple instabilities and modes of glacial rhythmicity in the plio-Pleistocene: a general theory of late Cenozoic climatic change
Multiple instabilities and modes of glacial rhythmicity in the plio-Pleistocene: a general theory of late Cenozoic climatic change
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上更新世冰川节律的多重不稳定性和模式：晚新生代气候变化的一般理论
DOI：
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发表时间：
1993
期刊：
影响因子：
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通讯作者：
M. Verbitsky
中科院分区：
文献类型：
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作者：
B. Saltzman;M. Verbitsky
人们注意到，在过去的几百万年里，存在着几种不同的冰川振荡模式，从上新世早期的低振幅、高频率振荡，到上新世晚期和更新世早期的相对高振幅、主要是近40 ky周期的振荡，再到更新世晚期的主要近100 ky周期的振荡。除了以前提出的解释这种多节律现象的其他可能机制之外，我们现在说明这种行为的另一种可能的贡献者，这种贡献者基于这样的假设，即缓慢响应的气候系统是不稳定的，两种内部不稳定性可能沿着由地球轨道引起的外部强迫。（米兰科维奇）辐射的变化和缓慢的，构造引起的大气二氧化碳的变化。这两个不稳定性已经讨论过了：一个是由于全球碳循环的正反馈导致近100千公里的冰盖的自由振荡，另一个是由于潜在的冰崩解灾害与基岩的变化，可能会导致振荡的周期接近40千公里，独立于重力强迫。在包含这两种不稳定性以及稳定模式的可能性的动力学模型的框架内，我们展示了（1）米兰科维奇辐射变化或影响冰盖的随机强迫如何诱导可能的稳定和不稳定模式之间的非周期性（混沌）转变，更重要的是，（2）如何渐进的，长期的，构造诱导的二氧化碳变化，在北方高纬度地区与地球轨道辐射变化协同作用，可以迫使模式之间的系统转换。这种系统性的变化可能导致过去5百万年的冰量年表，在质量上类似于全球冰量的观测记录。从本质上讲，我们已经建立了一个最小的动力学模型的晚新生代气候变化，包含什么被认为是决定这些变化的主要物理因素：冰质量，基岩凹陷，大气二氧化碳浓度，深海温盐状态，米兰科维奇辐射强迫，和缓慢的构造引起的二氧化碳强迫。这一模型为这一漫长时期的复杂气候事件提供了一个连贯的理论基础。
It has been noted that several distinct modes of glacial oscillation have existed during the past few million years, ranging from low-amplitude, high-frequency oscillations in the early Pliocene, through relatively high amplitude, predominantly near-40 ky period, oscillations in the late Pliocene and early Pleistocene, to the major near-100 ky period oscillations of the late Pleistocene. In addition to other plausible mechanisms suggested previously to explain aspects of this multirhythmic phenomenon, we now illustrate another possible contributor to this type of behavior based on the hypothesis that the slow-response climatic system is bistable and that two kinds of internal instability may be operative along with externally imposed forcing due to earth-orbital (Milankovitch) radiation changes and slow, tectonically-induced changes in atmospheric carbon dioxide. These two instabilities have been discussed previously: one is due to positive feedback in the global carbon cycle leading to near-100 ky free oscillations of the ice sheets, and the other is due to the potential for ice-calving catastrophes associated with bedrock variations that can lead to oscillations of a period near 40 ky, independent of obliquity forcing. Within the framework of a dynamical model containing the possibility for these two instabilities, as well as for stable modes, we show (1) how Milankovitch radiative changes or stochastic forcing influencing ice sheets can induce aperiodic (chaotic) transitions between the possible stable and unstable modes, and more significantly, (2) how progressive, long-term, tectonically-induced, changes in carbon dioxide, acting in concert with earth-orbital radiative variations in high Northern Hemisphere latitudes, can force systematic transitions between the modes. Such systematic changes can result in an ice mass chronology for the past 5 My that is qualitatively similar to the observed record of global ice mass. In essence, we have constructed a minimum dynamical model of the late Cenozoic climatic changes, containing what are believed to be the main physical factors determining these changes: ice mass, bedrock depression, atmospheric carbon dioxide concentration, deep ocean thermohaline state, Milankovitch radiation forcing, and slow tectonically-induced carbon dioxide forcing. This model forms the basis for a coherent theory for the complex climatic events of this long period.