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

本研究将收集一个新的数据集，通过重建Waesche火山的冰川历史，确定西南极冰盖（WAIS）如何在末次间冰期（~ 125000年前）对变暖的气候做出反应。当冰原比现在小的时候，重建WAIS的几何结构是困难的，而且缺乏数据，因为证据在现在的冰原下面。这项研究将钻穿冰盖，恢复基岩，可以分析其表面暴露历史，以帮助确定表面何时被冰盖覆盖。该研究将为末次冰期-间冰期旋回期间WAIS的最大和最小空间范围提供约束条件。了解在地球比现在更暖的时间间隔内减少的WAIS的几何形状，可以在预测温度趋势的情况下为未来的环境条件提供可能的模拟。WAIS的减少导致海平面上升，威胁到全球沿海社区。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反应。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Waesche山（位于Marie Byrd Land的一座火山，靠近WAIS（海拔2000米）的冰丘）进行浅钻孔（80米），从WAIS下方获取岩石样本。暴露在火山侧面的熔岩流的岩性非常适合宇宙成因的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，火山侧面的玄武岩熔岩流早在350年前就存在了。因此，在冰下岩心中测量到的宇宙形成核素将表明在冰高度降低期间相对较近的暴露，最有可能是在最后一次间冰期。第一个实地季节的重点是确定钻探的适当地点，并对蓝色冰区100米以下的冰下地形进行探地雷达调查。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。第二季野外活动包括使用Winkie钻头在冰缘附近的蓝冰上钻8个钻孔（两个断面）至80 m深度，从冰下熔岩流中获取岩芯。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，这些证据将独立地限制过去喷发期间较低的冰水平。本研究的结果将与Waesche山模拟的冰高程历史进行比较，以验证冰盖模拟的成果。该奖项反映了美国国家科学基金会的法定使命，并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，被认为值得支持。

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.