COLLABORATIVE RESEARCH: Site Survey for Subglacial Bedrock Exposure Dating at the Margin of the Wilkes Basin in Northern Victoria Land

合作研究：维多利亚州北部威尔克斯盆地边缘冰下基岩暴露年代测定现场调查

• 批准号: 1744850
• 负责人: Claire Todd
• 金额: $ 12.57万
• 依托单位: Pacific Lutheran University
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2021
• 资助国家: 美国
• 起止时间: 2021-09-01 至 2022-01-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1744850&HistoricalAwards=false
• 关键词: COLLABORATIVE; RESEARCH; Site; Survey; Subglacial

The goal of this project is to establish, through direct geological evidence, whether complete deglaciation of East Antarctic marine basins took place during past warm-climate periods. Direct geological information about whether the Antarctic Ice Sheet responded catastrophically to past climate changes is important to evaluating the likelihood of significant ice-sheet response to future climate change. The team will assess the feasibility of achieving this goal using cosmogenic-nuclide measurements on bedrock that is currently buried under the ice sheet. They will conduct a reconnaissance and site survey to identify potential drill sites where subglacial bedrock-exposure dating could subsequently be used to test whether ice at those sites was absent when the Earth last experienced current levels of carbon dioxide—at approximately 3.0 to 3.3 million years ago.This project will seek out potential sites that can address whether total deglaciation of subglacial basins in coastal East Antarctica took place during past warm-climate periods like the middle Pliocene warm period at circa 3.0-3.3 Ma. Ice-sheet model simulations have identified marine ice-margin instability as a possible cause for higher eustatic sea level during this period. In general, it is difficult to obtain direct and unambiguous geological evidence that an ice sheet was smaller in the past because if such evidence exists it is most likely inaccessible beneath the present ice sheet. One means of overcoming this problem is to search for significant concentrations of cosmic-ray-produced radionuclides in bedrock surfaces beneath the present ice sheet. Such concentrations can only be produced if the surface is ice-free, so significant cosmogenic-nuclide concentrations would provide incontrovertible evidence that the ice sheet was smaller in the past, and, in addition, can provide information about when this occurred. Guided by ice-sheet model simulations of Pliocene deglaciation to identify areas where complete deglaciation of the Wilkes subglacial basin would cause substantial changes in the extent of bedrock exposure, the team will collect geophysical and geochemical data to identify and evaluate sites with potential for future bedrock recovery.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.

该项目的目标是通过直接的地质证据，确定在过去的温暖气候时期，南极东部海洋盆地是否发生了完全的消冰。关于南极冰盖是否对过去的气候变化作出了灾难性反应的直接地质信息，对于评估冰盖对未来气候变化作出重大反应的可能性非常重要。该小组将利用目前埋在冰盖下的基岩上的宇宙核素测量来评估实现这一目标的可行性。他们将进行一次勘察和现场调查，以确定潜在的钻探地点，在那里，冰川下的基岩暴露年代测定可以随后用于测试这些地点的冰是否在地球最近一次经历目前的二氧化碳水平时（大约300万到330万年前）不存在。该项目将寻找潜在的地点，以确定在过去的温暖气候时期，如大约3.0-3.3 Ma的上新世中期温暖时期，东南极洲沿海的冰下盆地是否发生了完全的冰川消融。冰盖模式模拟已经确定，海洋冰缘不稳定是这一时期海平面上升的一个可能原因。一般来说，很难获得直接和明确的地质证据来证明过去的冰原更小，因为即使存在这样的证据，也很可能无法在现在的冰原下面找到。克服这个问题的一种方法是在目前冰盖下的基岩表面寻找宇宙射线产生的大量放射性核素。这样的浓度只有在表面无冰的情况下才会产生，因此，显著的宇宙生成核素浓度将提供无可争议的证据，证明过去的冰盖更小，此外，还可以提供这种情况发生的时间的信息。在上新世冰川消融的冰盖模型模拟的指导下，确定威尔克斯冰川下盆地的完全冰川消融将导致基岩暴露程度发生实质性变化的区域，该团队将收集地球物理和地球化学数据，以确定和评估未来基岩恢复的潜力。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。