Raymo M E, Lisiecki L E, Nisancioglu Kerim H
Department of Earth Science, Boston University, 685 Commonwealth Avenue, Boston, MA 02215, USA.
Science. 2006 Jul 28;313(5786):492-5. doi: 10.1126/science.1123296. Epub 2006 Jun 22.
We propose that from approximately 3 to 1 million years ago, ice volume changes occurred in both the Northern and Southern Hemispheres, each controlled by local summer insolation. Because Earth's orbital precession is out of phase between hemispheres, 23,000-year changes in ice volume in each hemisphere cancel out in globally integrated proxies such as ocean delta18O or sea level, leaving the in-phase obliquity (41,000 years) component of insolation to dominate those records. Only a modest ice mass change in Antarctica is required to effectively cancel out a much larger northern ice volume signal. At the mid-Pleistocene transition, we propose that marine-based ice sheet margins replaced terrestrial ice margins around the perimeter of East Antarctica, resulting in a shift to in-phase behavior of northern and southern ice sheets as well as the strengthening of 23,000-year cyclicity in the marine delta18O record.
我们认为，大约在300万至100万年前，北半球和南半球都发生了冰量变化，每个半球的冰量变化都受当地夏季日照的控制。由于地球轨道岁差在两个半球之间不同步，每个半球23000年的冰量变化在全球综合代理指标（如海洋δ18O或海平面）中相互抵消，使得日照的同相位倾斜（41000年）分量在这些记录中占主导地位。只需南极洲有适度的冰量变化，就能有效抵消北半球大得多的冰量信号。在中更新世过渡时期，我们认为，以海洋为基础的冰盖边缘取代了东南极洲周边的陆地冰缘，导致南北冰盖向同相位行为转变，同时海洋δ18O记录中23000年周期性增强。
