Collaborative Research: Deglacial Ice Dynamics in the Weddell Sea Embayment using Sediment Provenance

合作研究：利用沉积物来源研究威德尔海海湾的冰川消融动力学

• 批准号: 1724670
• 负责人: Trevor Williams
• 金额: $ 24.89万
• 依托单位: Texas A&M University
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2016
• 资助国家: 美国
• 起止时间: 2016-09-01 至 2019-08-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1724670&HistoricalAwards=false
• 关键词: Collaborative; Research; Deglacial; Ice; Dynamics

Abstract for the general public:The margins of the Antarctic ice sheet have advanced and retreated repeatedly over the past few million years. Melting ice from the last retreat, from 19,000 to 9,000 years ago, raised sea levels by 8 meters or more, but the extents of previous retreats are less well known. The main goal of this project is to understand how Antarctic ice retreats: fast or slow, stepped or steady, and which parts of the ice sheet are most prone to retreat. Antarctica loses ice by two main processes: melting of the underside of floating ice shelves and calving of icebergs. Icebergs themselves are ephemeral, but they carry mineral grains and rock fragments that have been scoured from Antarctic bedrock. As the icebergs drift and melt, this 'iceberg-rafted debris' falls to the sea-bed and is steadily buried in marine sediments to form a record of iceberg activity and ice sheet retreat. The investigators will read this record of iceberg-rafted debris to find when and where Antarctic ice destabilized in the past. This information can help to predict how Antarctic ice will behave in a warming climate. The study area is the Weddell Sea embayment, in the Atlantic sector of Antarctica. Principal sources of icebergs are the nearby Antarctic Peninsula and Weddell Sea embayment, where ice streams drain about a quarter of Antarctic ice. The provenance of the iceberg-rafted debris (IRD), and the icebergs that carried it, will be found by matching the geochemical fingerprint (such as characteristic argon isotope ages) of individual mineral grains in the IRD to that of the corresponding source area. In more detail, the project will: 1. Define the geochemical fingerprints of the source areas of the glacially-eroded material using samples from each major ice stream entering the Weddell Sea. Existing data indicates that the hinterland of the Weddell embayment is made up of geochemically distinguishable source areas, making it possible to apply geochemical provenance techniques to determine the origin of Antarctica icebergs. Few samples of onshore tills are available from this area, so this project includes fieldwork to collect till samples to characterize detritus supplied by the Recovery and Foundation ice streams. 2. Document the stratigraphic changes in provenance of iceberg-rafted debris (IRD) and glacially-eroded material in two deep water sediment cores in the NW Weddell Sea. Icebergs calved from ice streams in the embayment are carried by the Weddell Gyre and deposit IRD as they pass over the core sites. The provenance information identifies which groups of ice streams were actively eroding and exporting detritus to the ocean (via iceberg rafting and bottom currents), and the stratigraphy of the cores shows the relative sequence of ice stream activity through time. A further dimension is added by determining the time lag between fine sediment erosion and deposition, using a new method of uranium-series isotope measurements in fine grained material. Technical abstract: The behavior of the Antarctic ice sheets and ice streams is a critical topic for climate change and future sea level rise. The goal of this proposal is to constrain ice sheet response to changing climate in the Weddell Sea during the three most recent glacial terminations, as analogues for potential future warming. The project will also examine possible contributions to Meltwater Pulse 1A, and test the relative stability of the ice streams draining East and West Antarctica. Much of the West Antarctic ice may have melted during the Eemian (130 to 114 Ka), so it may be an analogue for predicting future ice drawdown over the coming centuries. Geochemical provenance fingerprinting of glacially eroded detritus provides a novel way to reconstruct the location and relative timing of glacial retreat during these terminations in the Weddell Sea embayment. The two major objectives of the project are to: 1. Define the provenance source areas by characterizing Ar, U-Pb, and Nd isotopic signatures, and heavy mineral and Fe-Ti oxide compositions of detrital minerals from each major ice stream entering the Weddell Sea, using onshore tills and existing sediment cores from the Ronne and Filchner Ice Shelves. Pilot data demonstrate that detritus originating from the east and west sides of the Weddell Sea embayment can be clearly distinguished, and published data indicates that the hinterland of the embayment is made up of geochemically distinguishable source areas. Few samples of onshore tills are available from this area, so this project includes fieldwork to collect till to characterize detritus supplied by the Recovery and Foundation ice streams. 2. Document the stratigraphic changes in provenance of iceberg-rafted debris (IRD) and glacially-eroded material in two deep water sediment cores in the NW Weddell Sea. Icebergs calved from ice streams in the embayment are carried by the Weddell Gyre and deposit IRD as they pass over the core sites. The provenance information will identify which ice streams were actively eroding and exporting detritus to the ocean (via iceberg rafting and bottom currents). The stratigraphy of the cores will show the relative sequence of ice stream activity through time. A further time dimension is added by determining the time lag between fine sediment erosion and deposition, using U-series comminution ages.

对于公众来说，摘要：在过去的几百万年中，南极冰盖的边缘已经晋升并撤退。从19,000年前到9，000年前的最后一次静修会融化冰，将海平面提高了8米或更多，但以前的务虚会的范围却鲜为人知。 该项目的主要目的是了解南极冰的撤退是如何：快速或缓慢，步进或稳定，哪些部分最容易撤退。南极通过两个主要过程失去了冰：浮动冰架的底面融化和冰山的产犊。冰山本身就是短暂的，但它们携带矿物谷物和岩石碎片，这些岩石碎片已经从南极基岩搜寻。随着冰山的漂移和融化，这种“冰山羊碎片”落在海床上，并稳步地埋在海洋沉积物中，形成了冰山活动和冰盖静修的记录。调查人员将阅读此记录的冰山羊碎片记录，以查找过去南极冰的何时何地稳定。这些信息可以帮助预测南极冰在温暖的气候下如何行事。研究区域是南极大西洋地区的Weddell Sea Embayment。冰山的主要来源是附近的南极半岛和Weddell Sea Embayment，那里的冰溪流耗尽了大约四分之一的南极冰。将通过与IRD中各个矿物质的地球化学指纹（例如特征性的氩同位素年龄）匹配冰山羊皮碎屑（IRD）和携带它的冰山的出处。更详细的是，该项目将：1。使用进入Weddell Sea的每个主要冰流的样品来定义冰川化材料源区域的地球化学指纹。 现有数据表明，Weddell胚胎的腹地由地球化学上可区分的来源区域组成，因此可以应用地球化学出处技术来确定南极冰山的起源。该区域中很少有陆上耕种样品，因此该项目包括田野调查，以收集直到样品，以表征恢复和基础冰流提供的碎屑。 2。记录了西北韦德尔海的两个深水沉积物核心中冰山羊皮碎片（IRD）和冰川磨削材料的出处的地层变化。韦德尔·格雷（Weddell Gyre）从叶片中的冰流产量的冰山是在冰河上携带的，并沉积了ird，当它们通过核心地点时。出处信息确定了哪些冰流正在积极侵蚀并将碎屑出口到海洋（通过冰山漂流和底部电流），而岩心的地层图显示了随着时间的推移冰流活性的相对顺序。通过使用新的铀系列同位素测量方法在细粒料材料中确定细沉积物侵蚀和沉积之间的时间滞后，添加了进一步的维度。 技术摘要：南极冰盖和冰流的行为是气候变化和未来海平面上升的关键话题。该提案的目的是限制在最近三个冰川终止的三个最新冰川终止期间对韦德尔海气候变化的反应，作为潜在未来变暖的类似物。该项目还将检查对融合水脉冲1a的可能贡献，并测试排出东和南极的冰流的相对稳定性。在EEMIAN（130至114 ka）期间，南极西部的大部分地区可能已经融化，因此它可能是预测未来几个世纪未来冰量的类似物。冰川侵蚀的碎屑的地球化学指纹指纹为重建韦德尔海胚胎中这些终止期间冰川撤退的位置和相对时机提供了一种新颖的方法。该项目的两个主要目标是：1。通过表征AR，U-PB和ND同位素特征来定义出处源区域，以及来自每个主要冰流的碎屑矿物质的重矿物和Fe-Ti氧化物组成，进入Weddell海上，使用陆上耕种和现有的矿井中的矿床和菲尔奇纳冰架。试点数据表明，源自Weddell Sea Embayment的东部和西侧的碎屑可以明确区分，并且已发布的数据表明，胚胎的腹地由地球化学上可区分的源区域组成。该区域中很少有陆上耕种样品，因此该项目包括收集直到的现场工作，以表征恢复和基础冰流提供的碎屑。 2。记录了西北韦德尔海的两个深水沉积物岩心中冰山羊皮碎片（IRD）和冰川磨削物质的出处的地层变化。韦德尔·格雷（Weddell Gyre）从叶片中的冰流产量的冰山是在冰河上携带的，并沉积了ird，当它们通过核心地点时。这些出处信息将确定哪些冰流正在积极侵蚀并将碎屑出口到海洋（通过冰山漂流和底部电流）。核心的地层学将随着时间的流逝显示冰流活性的相对顺序。通过使用U系列粉刺年龄来确定细胞侵蚀和沉积之间的时间滞后，添加了进一步的时间维度。