EXPROBE-WAIS: Exposed Rock Beneath the West Antarctic Ice Sheet, A Test for Interglacial Ice Sheet Collapse

该奖项支持一个项目，以确定过去南极西部冰盖（WAIS）是否变薄和崩塌，如果是，这是什么时候发生的。地质学家对这个话题很感兴趣，他们长期研究冰盖的历史和行为（包括WAIS），以确定什么样的气候条件允许冰盖生存，什么样的条件导致它们在过去崩溃。这项研究的大部分集中在最后一个冰河时代，当时的气候条件比现在冷得多；这个项目将关注过去冰盖对变暖气候的反应。一种新的、具有潜在变革意义的方法是，对WAIS下面基岩中被宇宙射线转化的原子进行分析，从而对过去的无冰条件进行明确的测试。这是因为能够产生必要反应的宇宙射线只能穿透冰川冰层几米。因此，如果在当前冰盖表面以下数百米的样本中检测到它们，这将为过去大部分无冰状态提供明确的证据。不同深度的岩心中不同宇宙射线产物的浓度将有助于回答基岩暴露的频率、冰盖变薄的程度以及过去哪个时期产生了能够使冰盖不稳定的气候条件等问题。南极洲西部皮里特山附近冰盖下的短基岩岩芯将使用一种新的灵活的冰下地质钻机（能够钻到冰面下200米）收集，该钻机由冰钻探计划办公室（IDPO）开发，以支持该项目和其他项目。根据先前的勘测测绘、样本分析和冰盖床的雷达调查，已经确定了有利的钻井地点。在这项研究中收集的岩心将被分析宇宙射线产生的不同元素的同位素，其半衰期从5700年（C-14）到1.4 Myr (be -10)，以及稳定的Ne-21。这些同位素的存在与否将为基岩表面过去是否无冰提供一个明确的测试，由于它们的半衰期不同，同位素的比例将限制过去暴露事件的年龄、频率和持续时间。不同深度基岩表面的结果将表明过去冰盖减薄的程度。其目的是将过去冰川消融的证据与气候变暖的特定时期联系起来，从而衡量冰盖对已知气候条件的反应。该项目解决了冰盖对气候变暖的敏感性这一广泛问题，而这在很大程度上是由海平面记录间接确定的。相比之下，该项目将提供直接测量结果，为南极洲西部冰盖变薄提供证据。这项工作的结果将有助于确定未来可能危及西海地区的气候因素和阈值。该项目将对正在进行的气候变化、冰盖融化和相关海平面上升的研究作出重大贡献。这个项目在南极洲进行实地考察。

Stone/1341728This award supports a project to determine if the West Antarctic Ice Sheet (WAIS) has thinned and collapsed in the past and if so, when did this occur. This topic is of interest to geologists who have long been studying the history and behavior of ice sheets (including the WAIS) in order to determine what climatic conditions allow an ice sheet to survive and what conditions have caused them to collapse in the past. The bulk of this research has focused on the last ice age, when climate conditions were far colder than the present; this project will focus on the response of ice sheets to warmer climates in the past. A new and potentially transformative approach that uses the analysis of atoms transformed by cosmic-rays in bedrock beneath the WAIS will allow a definitive test for ice free conditions in the past. This is because the cosmic rays capable of producing the necessary reactions can penetrate only a few meters through glacier ice. Therefore, if they are detected in samples from hundreds of meters below the current ice sheet surface this would provide definitive proof of mostly ice-free conditions in the past. The concentrations of different cosmic ray products in cores from different depths will help answer the question of how frequently bedrock has been exposed, how much the ice sheet has thinned, and which time periods in the past produced climatic conditions capable of making the ice sheet unstable.Short bedrock cores beneath the ice sheet near the Pirrit Hills in West Antarctica will be collected using a new agile sub-ice geological drill (capable of drilling up to 200 meters beneath the ice surface) that is being developed by the Ice Drilling Program Office (IDPO) to support this and other projects. Favorable drilling sites have already been identified based on prior reconnaissance mapping, sample analysis and radar surveys of the ice-sheet bed. The cores collected in this study will be analyzed for cosmic-ray-produced isotopes of different elements with a range of half-lives from 5700 yr (C-14) to 1.4 Myr (Be-10), as well as stable Ne-21. The presence or absence of these isotopes will provide a definitive test of whether bedrock surfaces were ice-free in the past and due to their different half-lives, ratios of the isotopes will place constraints on the age, frequency and duration of past exposure episodes. Results from bedrock surfaces at different depths will indicate the degree of past ice-sheet thinning. The aim is to tie evidence of deglaciation in the past to specific periods of warmer climate and thus to gauge the ice sheet's response to known climate conditions. This project addresses the broad question of ice-sheet sensitivity to climate warming, which previously has been largely determined indirectly from sea-level records. In contrast, this project will provide direct measurements that provide evidence of ice-sheet thinning in West Antarctica. Results from this work will help to identify the climatic factors and thresholds capable of endangering the WAIS in future. The project will make a significant contribution to the ongoing study of climate change, ice-sheet melting and associated sea-level rise. This project has field work in Antarctica.