ABSTRACT

The Pleistocene glacial cycles are the most prominent climate variations over the past three million years. They are the climatic response to variations in the incoming solar radiation, insolation, due to the deviations of the Earth's orbital configuration from the perfect Keplerian orbit is caused by the influence of the other planets in the solar system. This climatic response to astronomical forcing is highly non-linear, which is most pronounced expressed in the changing duration of the glacial cycles through the Middle Pleistocene Transition around a million years ago, where the duration of glacial cycles changed from 40 kyr to approximately 100 kyr without any corresponding changes in the astronomical forcing. In the late Pleistocene glaciations, the Northern Hemisphere ice sheets have grown larger than before, causing an increased cooling through the ice-albedo feedback, which makes it harder with increased insolation to cause deglaciation. The cold climate with extended glaciations has also made the climate more unstable, where strong millennial-scale oscillations related to changes in the Atlantic Meridional Overturning Circulation are observed in the paleoclimatic records.

摘要

更新世冰川周期是过去 300 万年中最显着的气候变化。它们是对入射太阳辐射变化的气候反应，日照，由于地球的轨道配置与完美的开普勒轨道的偏差是由太阳系中其他行星的影响引起的。这种对天文强迫的气候响应是高度非线性的，这在大约一百万年前通过中更新世过渡期的冰川周期变化持续时间中表现得最为明显，其中冰川周期的持续时间从 40 kyr 变为大约 100 kyr天文强迫没有任何相应的变化。在更新世晚期的冰川作用中，北半球的冰盖变得比以前更大，通过冰反照率反馈导致冷却增加，这使得随着日照的增加更难导致冰川消融。冰期延长的寒冷气候也使气候更加不稳定，在古气候记录中观察到与大西洋经向翻转环流变化相关的千年尺度的强烈振荡。