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: 1744844
• 负责人: Gregory Balco
• 金额: $ 13.19万
• 依托单位: Berkeley Geochronology Center
• 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 2024-08-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1744844&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南极东部海洋盆地在过去的温暖气候时期是否发生了完全的冰川消退。关于南极冰盖是否对过去的气候变化做出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做出重大反应的可能性非常重要。该小组将利用目前埋藏在冰盖下的基岩的宇宙生成核素测量来评估实现这一目标的可行性。 他们将进行勘察和现场调查，以确定潜在的钻探地点，随后可以使用冰下岩石暴露年代测定法来测试这些地点的冰是否在地球上一次经历目前的二氧化碳水平时不存在。该项目将寻找潜在的地点，以解决南极洲东部沿海冰下盆地的冰川消融是否发生在大约300万至330万年前。在过去的温暖气候时期，如上新世中期温暖时期，约3.0-3.3 Ma。冰盖模型模拟已经确定，海洋冰缘不稳定是这一时期海平面上升的可能原因。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盖较小，因为如果存在这样的证据，很可能在现在的冰盖下无法进入。克服这一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放射性核素的显着浓度。 只有在表面没有冰的情况下才能产生这样的浓度，因此显着的宇宙生成核素浓度将提供无可争议的证据，表明过去冰盖较小，此外，还可以提供有关何时发生这种情况的信息。 在冰盖模型模拟上新世冰消作用的指导下，确定威尔克斯冰下盆地完全冰消作用将导致基岩暴露程度发生重大变化的地区，该小组将收集地球物理和地球化学数据，以确定和评估具有未来基岩恢复潜力的地点。该奖项反映了NSF的法定使命，并被认为值得通过使用基金会的知识价值和更广泛的影响审查标准。