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的数据集，以确定西南极冰盖（WAIS）如何在最后一个间冰期（约125，000年前）通过重建冰川历史来应对气候变暖。瓦舍火山。当冰盖比现在小的时候，重建WAIS的几何形状是困难的，而且缺乏数据，因为证据就在现在的冰盖下面。这项研究将钻透冰盖，恢复基岩，可以分析其表面暴露的历史，以帮助确定何时表面被冰盖覆盖。这项研究将提供末次冰期-间冰期循环期间WAIS过去最大和最小空间范围的限制。在地球比现在温暖的间隔期间，了解减少的WAIS的几何形状可能为预测的温度趋势提供未来环境条件的可能模拟。WAIS的减少导致海平面上升，威胁到地球仪的沿海社区。这些数据将有助于改进冰盖数值模型，以更好地预测WAIS对当前和未来气候趋势的反应。该项目支持教师教育研讨会和研究生和本科生的培训。该项目的目标是通过在Mt.韦舍火山，位于玛丽伯德地的一座火山，靠近韦伊斯的冰穹（海拔2000米）。火山侧翼暴露的熔岩流的岩性非常适合宇宙成因的3 He和36 Cl以及40 Ar/39 Ar测量，这将建立喷发和暴露年龄。现有的40 Ar/39 Ar数据表明，火山侧翼的玄武岩熔岩流的年龄为350万年。因此，在冰表面下的岩芯中测量的宇宙成因核素将指示在冰高度降低期间（最有可能是在最后一次间冰期期间）相对较新的暴露。第一个野外季节的重点是确定适当的钻探位置和对蓝冰区100米以下的冰下地形进行探地雷达（GPR）调查。对邻近的裸露熔岩流进行测绘和测年，将能够追踪冰缘以下已知年龄和成分的熔岩流，这将是下一年钻探的目标。第二个实地调查季节的活动包括在冰缘附近用Winkie钻8个钻孔（两个断面），钻到80米深的蓝冰中，从冰下熔岩流中获取岩芯。3 He暴露年龄将限制玛丽伯德地WAIS过去地表下降的持续时间和最小程度。更深的GPR成像（高达700米）将有望揭示熔岩/冰相互作用的额外证据，这些证据将在过去的喷发中独立地限制较低的冰水平。这项研究的结果将与模拟的冰海拔历史进行比较。该奖项反映了NSF的法定使命，并被认为值得通过使用基金会的知识价值和更广泛的影响审查标准进行评估来支持。