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

南极洲罗斯海湾自始至终的古冰流路径

• 批准号: 0118455
• 负责人: Lang Farmer
• 金额: $ 9.59万
• 依托单位: University of Colorado at Boulder
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2001
• 资助国家: 美国
• 起止时间: 2001-03-15 至 2004-08-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0118455&HistoricalAwards=false
• 关键词: Paleo; Ice; Flow; Paths; Till

0118455FarmerThis 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.

该奖项由极地项目办公室的南极地质和地球物理项目提供，支持一项研究罗斯海冰川-海洋沉积物的合作研究项目，以了解南极西部冰盖（WAIS）的历史。对西洋带未来对气候变化和海平面上升的响应的可靠预测，在很大程度上取决于提高我们对末次盛冰期（~ 18000年前）冰动力的认识和理解。来自南极洲罗斯海的沉积物包含了详细的物理记录，可以用来重建过去的冰川流动模式。尽管在限制冰的范围和最大范围的时间方面取得了重大进展，但冰流路径的重建存在很大差异。研究预测，主要来自南极西部的冰流（快速流动的冰区）是罗斯冰盖的主要特征，而冰盖模型重建显示，来自南极东部和西部冰的输入大致相等。这些冰源区域下面岩石类型和年龄的根本差异，应该有助于确定罗斯海斜坡的来源，从而促进过去冰流路径的重建。因此，罗斯湾提供了一个令人兴奋的机会，将现代冰流动力学与过去的冰盖动力学和沉积联系起来。通过将这些岩心沉积物的矿物学、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，将从罗斯海海底采集的岩心中收集的沉积物进行详细的物源研究。根据这些数据，可以限定末次盛冰期冰架冰流的模式。在这项研究中，将利用从罗斯海和南极洲东部和西部源区收集的现有样品。最后一次冰进期间沉积的沉积物的组成将通过检查沉积物的砂和卵石粒度组分、粘土矿物学、元素丰度和粉砂和粘土粒度组分的钐钕（Sm-Nd）同位素组成来表征。泥沙和粘土的来源可能是有问题的，因为大陆和海洋的来源可能混合在一起。这个问题将通过确定现代海洋样品的组成来解决，然后可以从样品组成中“减去”。首先对来自源区的样品进行分析，以确定每个区域的成分指纹。冰流路径将根据冰源区域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岩石矿物学和同位素组成诊断方面的横向和垂直变化特征，以便对了解过去3万年时间尺度上冰盖动力学的变化作出重大贡献。这项研究的结果将允许通过测试各种冰盖重建的有效性来评估冰流在最近的WAIS解体中发挥重要作用的假设。此外，更好地描述末次盛冰期罗斯冰盖的结构特征，将提高南极冰盖过去和未来行为特征模型的质量和可靠性。