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

这项研究将收集一个新的数据集，以确定西南极冰盖(WAIS)如何通过重建西南极冰盖(WAIS)的冰川历史来响应上一次间冰期(约12.5万年前)的气候变暖。威斯切火山。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。这项研究将钻探冰盖并恢复基岩，这些基岩可以分析其表面暴露历史，以帮助确定冰盖覆盖表面的时间。这项研究将提供对上一次冰川-间冰期循环期间WAIS过去最大和最小空间范围的限制。了解在地球温度高于现在的时间间隔内减少的WAIS的几何结构，可能会为未来的环境条件提供一个可能的类比，因为预测的温度趋势。WAIS的减少导致海平面上升，对全球沿海社区构成威胁。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。该项目支持教师培训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Mt.Wesche火山，玛丽·伯德大陆的一座火山，靠近WAIS(海拔2000米)的冰穹。暴露在火山侧面的熔岩流的岩性非常适合于宇宙成因的3He和36Cl以及40Ar/39Ar测量，这将确定火山喷发和暴露年龄。现有的40Ar/39Ar数据表明，早在350ka之前，玄武岩熔岩就在火山两侧流动。因此，在冰面下的岩芯中测量到的宇宙成因核素将表明，在冰川高度降低的时期，最有可能是在最后一次间冰期期间，相对较新的暴露。第一个实地考察季的重点是确定合适的钻探地点，并对蓝色冰层下100米处的冰下地形进行探地雷达(GPR)测量。对邻近裸露的熔岩流进行测绘和年代测定，将可以追踪冰缘下已知年龄和成分的熔岩流，这些熔岩流将在下一年进行钻探。第二个野外季节的活动包括用Winkie钻机在冰缘附近钻8个钻孔(两个横断面)穿过蓝冰，深度达到80米，以从冰下熔岩流中获取岩芯。3暴露年龄将制约玛丽·伯德地区过去WAIS地表下降的持续时间和最小程度。更深入的探地雷达成像(高达700米)将有望揭示熔岩/冰相互作用的更多证据，这将独立地限制过去喷发期间较低的冰层水平。这项研究的结果将与模拟的山顶冰高程历史进行比较。该奖项反映了NSF的法定使命，并通过使用基金会的智力优势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.