Expedition Objective Research: Early Pliocene Record Of Antarctic Ice Rafting And Paleoenvironmental Conditions, Wilkes Land Margin, Antarctica

探险目标研究：南极洲威尔克斯陆缘的上新世早期冰漂流记录和古环境条件

• 批准号: 1060080
• 负责人: Sandra Passchier
• 金额: $ 18.36万
• 依托单位: Montclair State University
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2011
• 资助国家: 美国
• 起止时间: 2011-03-15 至 2016-02-29
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1060080&HistoricalAwards=false
• 关键词: Expedition; Objective; Research; Early; Pliocene

Intellectual meritThis project investigates early Pliocene East Antarctic ice dynamics and paleoenvironmental conditions from variations in the production of ice-rafted debris and major element geochemistry of sediment cores collected during IODP Expedition 318 to the Wilkes Land margin of Antarctica. This portion of Antarctica carries the Wilkes and Aurora subglacial basins, where the East Antarctic Ice Sheet (EAIS) is grounded below sea level, and is potentially unstable. The early Pliocene is a known period of global warmth with sea surface temperatures ranging up to 5.5ºC higher than present in the Southern Ocean. The stability of the EAIS in this period of time is a major uncertainty and is considerably debated. Recent climate and ice-sheet modeling studies suggest that, in contrast to the West Antarctic Ice Sheet, the EAIS did not collapse during the Pliocene. However, the models do show that its margin retreated to within the present position and that the retreat generated a significant eustatic sea level component. The Wilkes Land margin is the location where the predicted retreat is the greatest. Here we collect a high-resolution record of IRD production, paleoproductivity, and changes in provenance, to 1) test the hypothesis of glacial retreat during early Pliocene warm periods; and 2) provide a record of sufficient resolution to correlate East Antarctic ice dynamics to global paleoclimatic proxies on 10kyr time scales. Two drillholes with well-dated early Pliocene intervals, Site U1358 on the continental shelf, and Site U1359 on the continental rise, are investigated. Ice-rafted debris (IRD) mass accumulation rates (MAR) will be determined in combination with bulk terrigenous grain-size analyses for Site U1359. Particle size analysis will also aid in the interpretation of the diamictites on the shelf at Site U1358. The sediments at both sites have 5% terrigenous fraction, so that particulate scavenging by organisms on terrigenous sediment concentrations of Fe, Ti and Al is negligible and stable element ratios can be used to derive provenance information and local paleoproductivity and weathering proxies. The integrated datasets of IRD MAR, degree of chemical alteration through weathering, and paleoproductivity, will be used to assess variations in ice extent and paleoclimatic conditions along Wilkes Land and the adjacent ocean, through early Pliocene warm periods.Broader impactsThe Pliocene was the last epoch wherein the atmospheric pCO2 was similar to today?s partial pressure and global surface temperatures were higher than the modern with a larger than average degree of warming occurring at high latitudes. Tectonically and oceanographically the Earth was similar to today and the early Pliocene is, therefore, an excellent time interval to study the long-term stability of ice sheets in a world comparable to the present and the near future. The Antarctic ice sheets are important components of the global climate system, because of their high albedo and influence on sea ice formation, ocean circulation, and sea level. Satellite data suggest that the Antarctic ice sheets at present are losing mass and that mass loss has recently accelerated resulting in a present contribution to global sea level rise of ca. 0.3 mm/yr. Due to the short monitoring period, however, it is uncertain whether ice sheets are responding to the present warming or whether this is an expression of short-term perturbations in the icesheet system. Both short-term monitoring and the analyses of long-term trends in geological records are essential to provide a complete assessment of the state of the climate system. Important broader impacts of this work are further: 1) the availability of high resolution data on cryosphere dynamics for global climate studies, 2) the increased accessibility of the core material for other researchers who target short intervals with time intensive methods of analysis, 3) the PIs activities to inform researchers in urban and coastal management policy and the general public through lectures and local media outlets, and 4) education through research participation of two students of diverse backgrounds, which can be considered an importantlong-term benefit of this work.

该项目从冰筏碎片生产的变化和IODP 318远征南极洲威尔克斯陆缘期间收集的沉积物岩心的主要元素地球化学研究上新世早期东南极冰动力学和古环境条件。南极洲的这一部分承载着威尔克斯和奥罗拉冰下盆地，在那里，东南极冰盖（EAIS）位于海平面以下，并且可能不稳定。上新世早期是一个已知的全球变暖时期，海面温度比南大洋高出5.5ºC。EAIS在这段时间内的稳定性是一个主要的不确定性，并有相当大的争议。最近的气候和冰盖模拟研究表明，与西南极冰盖相反，EAIS在上新世没有崩溃。然而，模型显示，其边缘退缩到目前的位置，并产生了显着的海平面上升分量的撤退。威尔克斯地边缘是预测的后退最大的位置。在这里，我们收集了一个高分辨率的记录IRD生产，古生产力和变化的起源，1）测试的假设，冰川退缩在上新世早期温暖的时期;和2）提供足够的分辨率记录，东南极冰动力学相关的全球古气候代理10 kyr的时间尺度。对两个具有较好年代的上新世早期地层的钻孔，即位于大陆架上的U1358和位于大陆隆起上的U1359进行了研究。冰筏碎片（IRD）质量累积率（MAR）将结合现场U1359的散装陆源粒度分析来确定。粒度分析也有助于解释研究中心U1358大陆架上的杂砾岩。这两个站点的沉积物中有5%的陆源部分，因此，颗粒清除生物对陆源沉积物中的铁，钛和铝的浓度是可以忽略不计的稳定的元素比，可以用来获得物源信息和当地的古生产力和风化代理。IRD MAR的综合数据集，通过风化作用的化学蚀变程度，和古生产力，将被用来评估冰的范围和古气候条件的变化沿着威尔克斯土地和邻近的海洋，通过上新世早期的温暖时期。的分压和全球表面温度都高于现代，高纬度地区的变暖程度高于平均水平。在构造和海洋学上，地球与今天相似，因此上新世早期是研究与现在和不久的将来相当的世界中冰盖长期稳定性的绝佳时间间隔。南极冰盖是全球气候系统的重要组成部分，因为它们的高湿度和对海冰形成，海洋环流和海平面的影响。卫星数据表明，南极冰盖目前正在失去质量，质量损失最近加速，导致目前对全球海平面上升的贡献约为100亿美元。0.3毫米/年然而，由于监测周期短，目前还不确定冰盖是否对目前的变暖做出了反应，或者这是否是冰圈系统短期扰动的表现。短期监测和对地质记录长期趋势的分析对于全面评估气候系统的状况至关重要。这项工作的更广泛的重要影响还包括：1）全球气候研究中冰冻圈动态的高分辨率数据的可用性，2）以时间密集型分析方法为目标的其他研究人员更容易获得核心材料，3）PI活动通过讲座和当地媒体向城市和沿海管理政策研究人员和公众提供信息，和4）通过两名不同背景的学生参与研究进行教育，这可以被认为是这项工作的一个重要的长期利益。