A physical record of the circumpolar circulation of the Southern Ocean - late Miocene to Pleistocene

这项工作将加深我们对深海环流在晚新生代重要气候变化方面的变化的理解。今天，三大洋的深水融入了南极绕极洋流(ACC)，因为它们不断地从一个洋盆输送到下一个洋盆以东。这股水流现在约为每秒1亿至1.5亿立方米，负责大西洋、印度洋和太平洋深海之间的大部分热量和营养物质的传输。ACC还将南极洲与北方温暖的世界隔离开来，其表面的水为该大陆提供了水分。因此，仔细构建这种流动的历史将大大增加我们对晚新生代全球变化的理解。我们建议开发一份详细的南极绕极洋流的物理记录，该洋流横跨过去9英里。为了实现这一点，我们将把在其他地方研究深海漂流沉积物中开发的方法应用于南极半岛太平洋边缘的ODP178号腿回收的漂流沉积物。由178航段的科学小组产生的数据，以及我们的初步信息，表明这些沉积物是海洋事件的忠实监测器。我们分析的主要工具将是磁化率各向异性(AMS)，这是对沉积物中组构或排列程度的定量测量。我们和其他人已经证明，更强的洋流会产生更明显的布料。将产生的其他数据包括：陆源沉积物组分的粒度分布，从而能够区分漂移相关沉积物和远端浊积岩；陆源沉积物在每个样品中的重量百分比，以及通过这种双组分沉积物的不同，蛋白石的数量；这些组分的质量积累速率；通过将组构信息定向到同一样品中记录的磁场矢量，确定流动的方向。这项工作的教育影响集中在这项研究将为其提供博士论文项目的研究生身上，但也包括本科生参与实践研究。

This work will increase our understanding of how deep-ocean circulation has changed with respect to important climate changes of the late Cenozoic. Today, deep waters of the three oceans blend in the Antarctic Circumpolar Current (ACC) as they are continually transported from one ocean basin to the next one east. This flow, now about 100 to 150 million cubic meters per second, is responsible for most of the heat and nutrient transport among the deep Atlantic, Indian and Pacific Oceans. The ACC also isolates Antarctica from the warmer world to the north and its surface waters provide moisture to the continent. As such, a carefully constructed history of this flow would significantly increase our understanding of late Cenozoic global change. We propose to develop a detailed physical record of the Antarctic Circumpolar Current that spans the last 9 Myr. To achieve this we will apply the methods developed in studying deep-sea drift deposits elsewhere to the drift sediments recovered by ODP Leg 178 on the Pacific margin of the Antarctic Peninsula. Data generated by the scientific party of Leg 178, along with our preliminary information, suggest that these deposits are a faithful monitor of ocean-wide events. The primary tool of our analysis will be the anisotropy of magnetic susceptibility (AMS) which is a quantitative measure of the fabric--or degree of alignment--in a sediment. We and others have shown that stronger currents result in more pronounced fabrics. Other data to be generated will include: the grain-size distribution of the terrigenous sediment component, which allows discrimination between drift-related sediments and distal turbidites; the weight percent of terrigenous sediment in each sample, and by difference in this two-component deposit, the amount of opal; the mass accumulation rate of these components; and by orienting the fabric information to the magnetic field vector recorded in the same sample, the direction of the flow. The educational impact of this work centers on the graduate student for whom this research will provide a Ph.D. thesis project, but also involves undergraduates in hands-on research.