Antarctic ice-sheet dynamics of the early Miocene

拟议项目的主要目标是严格测试现有的早中新世海平面/冰量重建，提供高质量的南极冰盖波动的定量估计，并获得对导致早中新世观察到的冰盖动态过程的机械理解。此外，它将被测试，如果不断变化的南极地形降低了南极大陆的能力，以支持一个比今天更大的AIS在中新世早期，导致一个更动态的AIS比渐新世晚期。这些目标将通过生成中新世早期（19.722-17.533 Ma）特定时间间隔的古气候代用记录来实现。要生成的代理记录的基础上底栖有孔虫地球化学（镁/钙和稳定同位素）重建海水中的变化delta 18 O（delta 18 Osw）-大陆冰量的代理。拟议的亚轨道分辨率记录将从远征342站点U1406（北大西洋纽芬兰附近）生成，目的是记录和了解受生命力调节的南极冰盖的动态和演变。提供这一信息将使我们能够详细了解新生代气候演变的关键间隔（即，中新世早期的动态气候）。此外，这些数据将允许一个复杂的比较背后的驱动机制冰川/间冰期周期在两个根本不同的间隔地球的历史，其气候过程：单极冰川早中新世和两极冰川晚更新世。简而言之，拟议的项目将解决以下主要研究问题：（1）早中新世冰量/海平面变化率是多少？(2)南极大陆不断变化的地形是否导致了一个更动态的AIS？(3)单极与双极冰川气候系统之间冰川/间冰期三角洲18 OSW变化的幅度是否具有可比性？中新世早期冰川与更新世冰川的可比性如何？

The principal objectives of the proposed project are to critically test available early Miocene sea-level/ice-volume reconstructions, to provide high-quality quantitative estimates of Antarctic ice-sheet fluctuations, and to obtain a mechanistic understanding of the processes that led to the ice-sheet dynamics observed for the early Miocene. Furthermore, it will be tested if the evolving Antarctic topography decreased the ability of the Antarctic continent to support a larger-than-today AIS in the early Miocene; leading to an even more dynamic AIS than compared to the late Oligocene. These objectives will be reached through the generation of paleoclimate proxy records for a specific time interval of the early Miocene (19.722-17.533 Ma). Proxy records to be generated are based on benthic foraminiferal geochemistry (Mg/Ca and stable isotopes) to reconstruct changes in seawater delta18O (delta18Osw) - a proxy for continental ice-volume. The proposed suborbital-resolution records will be generated from Expedition 342 Site U1406 (off Newfoundland, North Atlantic) and aim to document and understand the dynamics and evolution of obliquity-modulated Antarctic ice sheets. Providing this information will allow detailed insight into the evolution of the cryosphere for a critical interval of Cenozoic climate evolution (i.e., the dynamic climate of the early Miocene). Moreover, the data will allow a sophisticated comparison of the driving mechanisms behind glacial/interglacial cycles during two fundamentally different intervals of Earth’s history with respect to their climatic processes: the unipolar-glaciated early Miocene and the bipolar-glaciated Late Pleistocene. In short, the proposed project will address the following major research questions: (1) what was the rate of early Miocene ice-volume/sea-level variability? (2) does the evolving topography of the Antarctic continent lead to a more dynamic AIS? (3) is the amplitude of glacial/interglacial delta18Osw changes comparable between a unipolar vs. bipolar glaciated climate system? and (4) to what extent are early Miocene glacials comparable to those from the Pleistocene?