Collaborative Research: Constraining West Antarctic Ice Sheet Elevation during the last Interglacial

合作研究：限制末次间冰期期间南极西部冰盖的海拔

• 批准号: 1744927
• 负责人: Jerry Mitrovica
• 金额: $ 18.77万
• 依托单位: Harvard University
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2018
• 资助国家: 美国
• 起止时间: 2018-09-01 至 2024-08-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1744927&HistoricalAwards=false
• 关键词: Collaborative; Research; Constraining; West; Antarctic

This study will collect a novel dataset to determine how the West Antarctic Ice Sheet (WAIS) responded to a warmer climate during the last interglacial period (~125,000 years ago) by reconstructing the glacial history at the Mt. Waesche volcano. Reconstructing WAIS geometry when the ice sheet was smaller than present is difficult and data are lacking because the evidence lies beneath the present ice sheet. This study will drill through the ice sheet and recover bedrock that can be analyzed for its surface exposure history to help determine when the surface became overridden by the ice sheet. This study will provide constraints on the past maximum and minimum spatial extent of WAIS during the last glacial-interglacial cycle. Understanding the geometry of a reduced WAIS during intervals when the planet was warmer than present may provide a possible analogue for future environmental conditions given predicted temperature trends. A reduction of WAIS results in rising sea levels which threatens coastal communities across the globe. The data will help improve numerical ice sheet models to better predict WAIS response to current and future climate trends. The project supports a teacher educational workshop and the training of graduate and undergraduate students.The goal of this project is to obtain rock samples from beneath the WAIS through shallow (80 m) drilling at Mt. Waesche, a volcano in Marie Byrd Land, near an ice dome of WAIS (2000 m elevation). The lithologies of lava flows exposed on the flank of the volcano are well-suited for cosmogenic 3He and 36Cl as well as 40Ar/39Ar measurements which will establish eruption and exposure age. Existing 40Ar/39Ar data indicate basaltic lava flows on the volcano flank as young as 350 ka. Thus, measured cosmogenic nuclides measured in rock cores from beneath the ice surface will be indicative of relatively recent exposure during periods of reduced ice elevation, most likely, during the last interglacial. The first field season is focused on identifying appropriate locations for drilling and a ground penetrating radar (GPR) survey of the subglacial topography 100m under the blue ice area. Mapping and dating the adjacent exposed lava flows will allow tracing of lava flows of known age and composition below the ice margin that will be targeted for drilling the following year. The second field season activities include drilling 8 boreholes (two transects) through blue ice with the Winkie drill near the ice margin to 80 m depth to obtain rock cores from the sub-ice lava flows. 3He exposure ages will constrain the duration and minimum extent of past surface lowering of the WAIS in Marie Byrd Land. Deeper GPR imaging (up to 700 m) will hope to reveal additional evidence of lava/ice interactions that would independently place constraints on lower ice levels during past eruptions. Results from this study will be compared with the modeled ice elevation histories at Mt. Waesche to validate ice sheet modeling efforts.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.

这项研究将收集一个新颖的数据集，通过重建韦什火山的冰川历史来确定西南极冰盖 (WAIS) 如何应对最后一个间冰期（约 125,000 年前）的变暖气候。当冰盖比现在更小时，重建 WAIS 几何结构非常困难，并且缺乏数据，因为证据位于当前冰盖之下。这项研究将钻穿冰盖并回收基岩，对其表面暴露历史进行分析，以帮助确定表面何时被冰盖覆盖。这项研究将为末次冰期-间冰期旋回期间 WAIS 过去的最大和最小空间范围提供约束。了解地球比现在温暖的时间间隔内 WAIS 减少的几何形状，可以为未来的环境条件（给定预测的温度趋势）提供一个可能的类比。 WAIS 的减少导致海平面上升，威胁着全球沿海社区。这些数据将有助于改进数值冰盖模型，以更好地预测 WAIS 对当前和未来气候趋势的响应。该项目支持教师教育讲习班以及研究生和本科生的培训。该项目的目标是通过在韦什山（Mt. Waesche）浅层（80 m）钻探从 WAIS 下方获取岩石样本，该火山位于玛丽伯德地 (Marie Byrd Land) 附近。 WAIS 的冰穹（海拔 2000 米）。火山侧面暴露的熔岩流岩性非常适合宇宙成因 3He 和 36Cl 以及 40Ar/39Ar 测量，这些测量将确定喷发和暴露年龄。现有的 40Ar/39Ar 数据表明，火山侧翼的玄武岩熔岩流早在 350ka 就已存在。因此，在冰面下方的岩芯中测量的宇宙成因核素将表明在冰海拔降低期间（最有可能是在最后一次间冰期）相对较新的暴露。第一个野外季节的重点是确定合适的钻探位置以及对蓝冰区域下方 100m 的冰下地形进行探地雷达 (GPR) 调查。对邻近暴露的熔岩流进行测绘和测年将有助于追踪冰缘以下已知年龄和成分的熔岩流，这些熔岩流将在明年进行钻探。第二个野外季节活动包括使用 Winkie 钻机在蓝冰上钻 8 个钻孔（两个横断面），靠近冰缘至 80 m 深度，以从冰下熔岩流中获取岩芯。 3He 暴露年龄将限制 Marie Byrd Land WAIS 过去地表下降的持续时间和最小程度。更深的探地雷达成像（高达 700 m）将希望揭示熔岩/冰相互作用的额外证据，这些证据将独立地限制过去火山喷发期间较低的冰层水平。这项研究的结果将与韦什山模拟的冰高度历史进行比较，以验证冰盖建模工作。该奖项反映了 NSF 的法定使命，并通过使用基金会的智力价值和更广泛的影响审查标准进行评估，被认为值得支持。