Collaborative Research: EAGER: Dating Glacier Retreat and Readvance near Mount Waesche, West Antarctica

在最近两个冰期（125 000年前），全球气温和海平面都比今天高，获得关于南极西部冰盖大小的冰川学和地质学数据，直接限制了冰盖对气候变暖的反应。 这些数据也为预测未来海平面的冰盖模型提供了验证点。 然而，获得这些数据是困难的，因为冰期之间的冰范围的证据位于现在的冰面以下。确定这一冰范围的一个关键位置是瓦舍山，这是一座火山，位于冰盖圆顶附近的冰面之上。 为了准备钻透冰层，从冰盖下延伸的熔岩流中获取岩芯，该团队先前使用探地雷达来绘制冰下地形和内部冰川分层。 这些雷达剖面显示了冰内的不连续性，这代表了可能在最后两个冰期之间发生的较低的冰水平。 通过该奖项增加的冰芯工作旨在通过测定冰中的不连续性来加强该团队在瓦舍山的岩芯钻探计划。 了解这些间断的年龄将为过去的冰水平提供独立的证据。在南极洲其他地方的雷达剖面图中也观察到了类似的内部冰川不连续性;如果研究小组在韦舍山成功测定了它们的年代，这项技术可能会在南极洲更广泛地应用于限制较低的冰盖水平。为了最大限度地提高该项目钻岩部分的科学回报，研究小组将收集和分析冰样本，以限制冰内不整合面的年代。具体来说，该团队将使用Eclipse Drill获得包括冰内不整合面的垂直冰芯，并使用水平冰挖沟机对暴露的冰内火山灰地层进行采样，这些地层可以追溯到118，000年前。 该小组将使用雷达将由此产生的表面年代学外推到地下深度，提供地层学的横向深度年龄限制。 同位素和火山灰分析将用于提供冰芯的年龄限制。这些数据将与其他日期明确的西南极冰芯相关联，以获得当地的年表和不整合面的日期。这项探索性工作的目标是提供补充冰下岩芯结果的数据，以更好地限制自末次间冰期以来的地表高程变化，包括后退和再前进。该奖项反映了NSF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。

Obtaining glaciological and geologic data on the size of the West Antarctic Ice Sheet between the last two glacial periods (125,000 years ago), when global temperatures and sea level were higher than today, provides direct constraints on the ice sheet’s response to warmer climate. These data also provide validation points for ice-sheet models used to project future sea level. However, obtaining these data is difficult as the evidence for between glacial period ice extent lies below the present ice surface. A key location for determining this ice extent is Mount Waesche, a volcano that rises above the ice surface near the dome of the ice sheet. In preparation for drilling through the ice to obtain rock cores from lava flows that extend under the ice sheet, the team previously used ground-penetrating radar to map the sub-ice topography and internal glacial layering. These radar profiles revealed discontinuities within the ice that represent lower ice levels that may have occurred during the last between glacial periods. The ice-core work to be added through this award aims to enhance the team’s rock core drilling program at Mount Waesche by dating the discontinuities in the ice. Knowing the age of the discontinuities would provide independent evidence for past ice levels. Similar internal glacial discontinuities have been observed in radar profiles elsewhere in Antarctica; if the team is successful dating them at Mount Waesche, the technique could have wider application for constraining lower ice-sheet levels across Antarctica.To maximize scientific return from the rock-drilling portion of the project, the team will collect and analyze ice samples to constrain the ages of englacial unconformities. Specifically, the team will obtain vertical ice cores that include the englacial unconformities using the Eclipse Drill and surface horizontal cores that sample exposed englacial tephra stratigraphy extending back to 118,000 years before present using a horizontal ice trencher. The team will extrapolate the resulting surface chronology to subsurface depths using radar, providing lateral depth-age constraints of stratigraphy. Isotopic and tephra analysis will be used to provide age constraints on the ice cores. These data will be correlated with other, well-dated West Antarctic ice cores to obtain a local chronology and date the unconformities. The goal of this exploratory work is to provide data that complement the results from subglacial rock cores to better constrain surface-elevation change, including both retreat and readvance, since the last interglacial.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.