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中新世早期海平面/冰量重建，对南极冰盖波动提供高质量的定量估计，并从机制上了解导致观测到的中新世早期冰盖动力学的过程。此外，将检验不断演变的南极地形是否降低了南极大陆在中新世早期支持比今天更大的AIS的能力；导致比渐新世晚期更具活力的AIS。这些目标将通过生成早中新世(19.722-17.533 Ma)特定时间段的古气候替代记录来实现。将生成的替代记录基于海底有孔虫地球化学(镁/钙和稳定同位素)，以重建海水Delta18O(Delta18Osw)的变化--大陆冰量的替代。拟议的亚轨道分辨率记录将从远征342号站点U1406(北大西洋纽芬兰附近)产生，旨在记录和了解倾角调制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时期(即中新世早期的动态气候)冰冻圈的演化情况。此外，这些数据将允许对地球历史上两个根本不同的气候过程时期的冰川/间冰期周期背后的驱动机制进行复杂的比较：单极冰川作用的中新世早期和两极冰川作用的晚更新世。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)南极大陆不断演变的地形是否导致更具活力的AIS？(3)单极和两极冰川气候系统之间，冰川/间冰川三角洲变化的幅度是否相当？以及(4)早中新世冰川在多大程度上与更新世冰川相似？

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?