Collaborative Research: Paleo Ice Flow Paths from Till Provenance in the Ross Embayment, Antarctica

0003600 Licht该奖项由极地项目办公室南极地质和地球物理项目提供，支持一个合作研究项目，研究罗斯海的冰川海洋沉积物，以了解南极西部冰盖（WAIS）的历史。WAIS对气候变化和海平面上升的未来响应的可靠预测在很大程度上取决于我们对末次盛冰期（约18，000年前）冰动力学的认识和理解。 南极洲罗斯海的沉积物包含详细的物理记录，可用于重建过去的冰川流动模式。虽然在限制冰的范围及其最大范围的时间方面取得了重大进展，但冰流路径的重建差异很大。研究预测，主要来自西南极洲的冰流（快速流动的冰）是罗斯冰盖的主要特征，而冰盖建模重建显示，东南极洲和西南极洲的冰输入大致相等。这些源区下面的岩石类型和年龄的根本差异应该允许罗斯海的冰碛物的来源被确定，促进过去的冰流路径的重建。因此，罗斯湾为将现代冰流动力学与过去冰盖动力学和沉积物联系起来提供了一个令人兴奋的机会。通过将这些岩心中沉积物的矿物学、地球化学和同位素特征与从可能的源区收集的参考沉积物联系起来，将对从罗斯海底采集的岩心中收集的沉积物进行详细的物源研究。从这些数据中，冰流穿过大陆架的模式可以被限制为末次冰期最大。在这项研究中，将利用从罗斯海以及东南极洲和西南极洲源区收集的现有样本。组成的冰碛沉积在最后一个冰前进的特点是检查砂和卵石粒度级的沉积物，粘土矿物学，元素丰度和钐钕（Sm-Nd）同位素组成的粉砂和粘土粒度级。粉砂和粘土部分的来源可能是有问题的，因为可能混合了大陆和海洋来源。这个问题将通过确定现代海洋样品的成分来解决，然后可以从冰碛物成分中“减去”，首先将分析来源地区的样品，以确定每个地区的成分指纹。冰流路径将根据源区与罗斯海测量值之间的对应关系来确定。该项目的目标是描述冰碛物矿物学和同位素组成诊断方面的横向和垂直变化，以便为理解过去30年时间尺度上冰盖动态变化做出重大贡献，这项研究的结果将允许评估的假设，冰流发挥了重要作用，在最近解体的WAIS，测试各种冰盖重建的有效性。此外，更好地描述末次盛冰期罗斯冰盖的结构将提高南极冰盖行为过去和未来特征模型的质量和可靠性。

0003600LichtThis award, provided by the Antarctic Geology and Geophysics Program of the Office of Polar Programs, supports a collaborative research project to study glacio-marine sediments from the Ross Sea toward an understanding of the history of the West Antarctic Ice Sheet (WAIS). Reliable predictions of the future response of the WAIS to changing climate and rising sea level depend, to a large extent, on improving our knowledge and understanding of its ice dynamics during the last glacial maximum (~18,000 yrs ago). Sediments from the Ross Sea, Antarctica, contain a detailed physical record that can be used to reconstruct past glacier flow patterns. Although significant progress has been made in constraining the extent of ice and the timing of its maximum extent, reconstructions of ice flow paths vary substantially. Studies have predicted that ice streams (regions of fast flowing ice) derived primarily from West Antarctica were dominant features of the Ross Ice Sheet, whereas an ice sheet modeling reconstruction showed roughly equal input from East and West Antarctic ice. Fundamental differences in rock types and ages beneath these source areas should allow the provenance of tills across the Ross Sea to be determined, facilitating the reconstruction of past ice flow paths. Thus the Ross Embayment provides an exciting opportunity to relate modern ice flow dynamics to past ice sheet dynamics and deposits.A detailed provenance study of sediment collected in cores taken from across the Ross Sea floor will be carried out by linking the mineralogical, geochemical, and isotopic characteristics of the sediments from these cores to reference sediments collected from the probable source areas. From these data, the patterns of ice flow across the shelf can be constrained for the last glacial maximum. For this study, existing samples collected from the Ross Sea, and the source areas of East and West Antarctica will be utilized. Composition of the till deposited during the last ice advance will be characterized by examining the sand and pebble size fraction of the sediment, the clay mineralogy, elemental abundance and samarium-neodymium (Sm-Nd) isotopic composition of the silt and clay size fraction. The source of silt and clay fraction may be problematic because of possible mixing of continental and marine sources. This problem will be addressed by determining the composition of modern marine samples which can then be 'subtracted' from the till composition.Samples from the source areas will be analyzed first to determine the compositional fingerprint of each area. Ice flow paths will be determined based on the correspondence between the source areas and the measured values across the Ross Sea. The goal of this project is to characterize both lateral and vertical variations in diagnostic aspects of till mineralogy and isotopic composition in order to make a significant contribution to the understanding of changes in ice sheet dynamics on time scale of the past 30,000 years.Results of this study will allow assessment of the hypothesis that ice streams played a significant role in the most recent disintegration of the WAIS by testing the validity of various ice sheet reconstructions. Additionally, better characterization of the configuration of the Ross Ice Sheet during the last glacial maximum will improve the quality and reliability of models of the past and future characteristics of Antarctic ice sheet behavior.