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.

智力绩效该项目研究了上新世东南极冰动力学和古环境条件，从冰上生产的碎屑生产的变化以及在IODP Expedition 318期间收集到的冰原岩心的主要元素地球化学，向北极地区的Wilkes Land Margin收集的沉积物核心。南极的这一部分带有威尔克斯和奥罗拉亚冰川贝斯，南极冰盖（EAIS）的海平面下于海平面以下，并且可能不稳定。上新世早期是一个已知的全球温暖时期，海面温度的范围比南大洋地区高出5.5ºC。 EAIS在这段时期的稳定性是一个主要的不确定性，被认为是辩论。最近的气候和冰片建模研究表明，与西南冰原相比，EAI在上新世期间没有崩溃。但是，这些模型确实表明其边缘退回到当前位置，并且撤退产生了显着的有效海平面成分。威尔克斯土地边缘是预测的务虚会最大的地方。在这里，我们收集了IRD产生，古生物生产率和预期变化的高分辨率记录，以测试上新世季节早期温暖时期冰川撤退的假设； 2）提供了足够的分辨率记录，以将东南极冰动力学与10公里时间尺度上的全球古气候代理相关联。投资了两个钻孔，具有良好的早期上新世间隔，连续架子上的站点U1358和连续升高的站点U1359进行了投资。冰的碎屑（IRD）质量积累速率（MAR）将结合用于现场U1359的散装式晶粒大小分析。粒度分析还将有助于解释位于U1358的架子上的脉冲岩。两个地点的沉积物均具有5％的陆源分数，因此，有机体在Fe，Ti和Al的陆源沉积物浓度上的特殊清除量可以忽略不计，并且可以使用稳定的元素比率来得出出处信息，以及局部的古生物生产力和效果代理。 IRD MAR的综合数据集，通过风化的化学改变程度以及古生产力将用于评估Wilkes Land和邻近海洋沿冰范围和古气候条件的变化，直到上新世早期的温暖时期。上新世比当今的平均水平更高，而在整体上，大气层的压力较高，而较高的是，大气层的压力要高。发生在高纬度地区。从构造和海洋上，地球与今天相似，因此，早期的上新世是研究冰盖在一个与现在和不久的将来相比的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，因为它们的反照率很高，并且对海冰形成，海洋循环和海平面的影响。卫星数据表明，目前南极冰盖正在损失质量，并且群众损失最近加速了，导致目前对CA的全球海平面上升的贡献。 0.3毫米/年。然而，由于监测期很短，尚不确定冰盖是否正在响应当前的变暖，还是这是ICESHEET系统中短期扰动的表达。短期监测和地质记录中长期趋势的分析对于提供气候系统状态的完整评估至关重要。 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 divers backgrounds, which can be considered an important long-term这项工作的好处。