Collaborative Research: Investigating Four Decades of Ross Ice Shelf Subsurface Change with Historical and Modern Radar Sounding Data

合作研究：利用历史和现代雷达探测数据调查罗斯冰架地下四个十年的变化

• 批准号: 2049302
• 负责人: Matthew Siegfried
• 金额: $ 31.75万
• 依托单位: Colorado School of Mines
• 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: 2021-08-15 至 2024-07-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=2049302&HistoricalAwards=false
• 关键词: Collaborative; Research; Investigating; Four; Decades

This award is funded in whole or in part under the American Rescue Plan Act of 2021 (Public Law 117-2).Ice shelves play a critical role in restricting the seaward flow of grounded glacier ice by providing buttressing at their bases and sides. Processes that affect the long-term stability of ice shelves can therefore influence the future contribution of the Antarctic Ice Sheet to global sea-level rise. The Ross Ice Shelf is the largest ice shelf on Earth, and it buttresses massive areas of West and East Antarctica. Previous studies of modern ice velocity indicated that the Ross Ice Shelf’s mass loss is roughly balanced by its mass gain. However, more recent work that extends further back in time reveals the ice shelf is likely not in steady state, with possible long-term thinning since the late 1990s. Consequently, to accurately interpret modern-day ice-shelf changes, long-term observations are critical to evaluate how these recent variations fit into the historical context of ice-shelf variability. This project will examine more than four decades of historical and modern airborne radar sounding observations of the Ross Ice Shelf (spanning 1971 to 2017) to investigate ice-shelf changes on decadal timescales. The team will process, calibrate, and analyze radar data collected during 1971-79 field campaigns and compare them against modern observations collected between 2011-17. They will estimate basal melt rates by examining changes in ice-shelf thickness, and will determine other important metrics for melt, including ice-shelf roughness, englacial temperature, and marine-ice formation. The project will support the education of a Ph.D. student at each of the three participating institutions. In addition, the project will support the training of undergraduate and high-school researchers in radioglaciology and Antarctic sciences.The project will test the hypothesis that, over decadal timescales, the basal melt rates beneath the Ross Ice Shelf have been low, particularly under shallow ice drafts, leading to overall thickening and increased buttressing potential. The team aims to provide a direct estimate of basal melt rates based on changes in ice-shelf thickness that occurred between 1971 and 2017. This project will extend similar work completed at Thwaites Glacier and improve the calibration methods on the vertical scaling for fast-time and depth conversion. The work will also leverage the dense modern surveys to improve the geolocation of radar film collected on earlier field campaigns to produce a more precise comparison of local shelf thickness with the modern data. In addition, the team will conduct englacial attenuation analysis to calculate englacial temperature to infer the trends in local basal melting. They will also examine the radiometric and scatterometric character of bed echoes at the ice-ocean boundary to characterize changes in ice-shelf basal roughness, marine-ice formation related to local basal freezing, and structural damage from fracture processes.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.

该奖项的全部或部分资金来自《2021年美国救援计划法案》(公法117-2)。冰架通过在冰架底部和侧面提供支撑，在限制地面冰川冰向大海流动方面发挥了关键作用。因此，影响冰架长期稳定的过程可能会影响南极冰盖未来对全球海平面上升的贡献。罗斯冰架是地球上最大的冰架，它支撑着南极洲西部和东部的大片地区。以前对现代冰速的研究表明，罗斯冰架的质量损失与其质量增加大致平衡。然而，更早的研究表明，冰架可能并不处于稳定状态，自20世纪90年代末以来，冰架可能会长期变薄。因此，为了准确地解释现代冰架的变化，长期观测对于评估这些最近的变化如何适应冰架变化的历史背景至关重要。该项目将研究40多年来对罗斯冰架的历史和现代机载雷达探测观测(从1971年到2017年)，以调查冰架在十年时间尺度上的变化。该团队将处理、校准和分析1971-79年野战期间收集的雷达数据，并将它们与2011-17年间收集的现代观测数据进行比较。他们将通过检查冰架厚度的变化来估计基本融化速度，并将确定其他重要的融化指标，包括冰架粗糙度、冰川温度和海冰形成。该项目将支持三所参与机构各培养一名博士生。此外，该项目将支持本科生和高中研究人员在放射冰川学和南极科学方面的培训。该项目将检验这样一个假设，即在十年的时间尺度上，罗斯冰架下的基础融化速度一直很低，特别是在浅冰吃水的情况下，导致整体增厚和支撑潜力增加。该团队的目标是根据1971至2017年间冰架厚度的变化，直接估计基本融化速度。该项目将扩展在Thwaites冰川完成的类似工作，并改进垂直标度的校准方法，以实现快速时间和深度转换。这项工作还将利用密集的现代调查，改进在早期实地活动中收集的雷达片的地理位置，以便更准确地将当地大陆架厚度与现代数据进行比较。此外，该小组将进行冰川衰减分析，以计算冰川温度，以推断当地底部融化的趋势。他们还将研究冰海交界处海床回波的辐射和散射特征，以表征冰架基面粗糙度的变化，与局部基面冻结相关的海洋冰形成，以及断裂过程造成的结构损害。这一奖项反映了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。