A 5 million year reconstruction of sea level, temperature, and sea water δ¹⁸O

Marine sediment records from the Oligocene and Miocene reveal clear 400,000-year (400-kyr) climate cycles related to variations in orbital eccentricity. These cycles are also observed in the Plio-Pleistocene records of the global carbon cycle. However they are absent in the Late Pleistocene ice-age record over the past 1.5 million years. Here, we present a simulation of global ice volume over the past 5 million years with a coupled system of four 3-D ice-sheet models. Our simulation shows that the 400-kyr long eccentricity cycles of Antarctica vary coherently with d13C records during the Pleistocene suggesting that they drive the long-term carbon cycle changes throughout the past 35 million years. The 400-kyr response of Antarctica is eventually suppressed by the dominant 100-kyr glacial cycles of the large ice sheets in the Northern Hemisphere (NH).

渐新世（Oligocene）与中新世（Miocene）的海洋沉积物记录清晰揭示了与轨道偏心率变化相关的40万年（400-kyr）气候周期。这类周期在全球碳循环的上新世-更新世（Plio-Pleistocene）记录中也有体现。然而在过去150万年的晚更新世（Late Pleistocene）冰期记录中，这类周期却并未出现。本研究借助包含四个三维冰盖模型的耦合系统，开展了过去500万年全球冰量的模拟实验。模拟结果显示，更新世（Pleistocene）期间南极地区的40万年尺度长偏心率周期与δ¹³C记录变化高度同步，表明该周期驱动了过去3500万年以来全球碳循环的长期演变。南极地区的40万年周期响应最终会被北半球（NH）大型冰盖主导的10万年尺度冰期周期所抑制。