Annual Satellite Era Accumulation Patterns Over WAIS Divide: A Study Using Shallow Ice Cores, Near-Surface Radars and Satellites

This award supports a project to broaden the knowledge of annual accumulation patterns over the West Antarctic Ice Sheet by processing existing near-surface radar data taken on the US ITASE traverse in 2000 and by gathering and validating new ultra/super-high-frequency (UHF) radar images of near surface layers (to depths of ~15 m), expanding abilities to monitor recent annual accumulation patterns from point source ice cores to radar lines. Shallow (15 m) ice cores will be collected in conjunction with UHF radar images to confirm that radar echoed returns correspond with annual layers, and/or sub-annual density changes in the near-surface snow, as determined from ice core stable isotopes. This project will additionally improve accumulation monitoring from space-borne instruments by comparing the spatial-radar-derived-annual accumulation time series to the passive microwave time series dating back over 3 decades and covering most of Antarctica. The intellectual merit of this project is that mapping the spatial and temporal variations in accumulation rates over the Antarctic ice sheet is essential for understanding ice sheet responses to climate forcing. Antarctic precipitation rate is projected to increase up to 20% in the coming century from the predicted warming. Accumulation is a key component for determining ice sheet mass balance and, hence, sea level rise, yet our ability to measure annual accumulation variability over the past 5 decades (satellite era) is mostly limited to point-source ice cores. Developing a radar and ice core derived annual accumulation dataset will provide validation data for space-born remote sensing algorithms, climate models and, additionally, establish accumulation trends. The broader impacts of the project are that it will advance discovery and understanding within the climatology, glaciology and remote sensing communities by verifying the use of UHF radars to monitor annual layers as determined by visual, chemical and isotopic analysis from corresponding shallow ice cores and will provide a dataset of annual to near-annual accumulation measurements over the past ~5 decades across WAIS divide from existing radar data and proposed radar data. By determining if temporal changes in the passive microwave signal are correlated with temporal changes in accumulation will help assess the utility of passive microwave remote sensing to monitor accumulation rates over ice sheets for future decades. The project will promote teaching, training and learning, and increase representation of underrepresented groups by becoming involved in the NASA History of Winter project and Thermochron Mission and by providing K-12 teachers with training to monitor snow accumulation and temperature here in the US, linking polar research to the student's backyard. The project will train both undergraduate and graduate students in polar research and will encouraging young investigators to become involved in careers in science. In particular, two REU students will participate in original research projects as part of this larger project, from development of a hypothesis to presentation and publication of the results. The support of a new, young woman scientist will help to increase gender diversity in polar research.本项目获该奖项资助，旨在通过处理2000年美国国际横穿南极科学考察（ITASE）航线上采集的现有近地表雷达数据，以及采集并验证深度约15米的近地表层的超/特高频（UHF）雷达图像，拓展对西南极冰盖（West Antarctic Ice Sheet, WAIS）年度积累模式的认知，将近年年度积累模式的监测能力从点源冰芯拓展至雷达测线。研究团队将同步采集浅冰芯与UHF雷达图像，以验证雷达回波与近地表积雪的年度层理、次年度密度变化（通过冰芯稳定同位素分析确定）的对应关系。此外，本项目还将把空间雷达反演得到的年度积累时间序列与覆盖南极大部分区域、时长超30年的被动微波时间序列进行对比，以此优化星载仪器的积累监测能力。本项目的学术价值在于，绘制南极冰盖积累速率的时空变化图谱，是理解冰盖对气候强迫响应的核心前提。据预测，未来百年南极降水速率将因气候变暖提升最高20%。积累量是决定冰盖质量平衡、进而影响海平面上升的关键参数，但在卫星时代的过去50年里，人类对年度积累变异性的监测手段仍主要局限于点源冰芯。本项目研发的基于雷达与冰芯的年度积累数据集，将为星载遥感算法、气候模型提供验证数据，并确立区域积累趋势。本项目的广义社会影响体现为：通过验证UHF雷达监测年度层理的可行性（结合对应浅冰芯的目视、化学与同位素分析），推动气候学、冰川学与遥感学界的研究发现与认知深化；基于现有雷达数据与拟采集的雷达数据，构建西南极冰盖分水岭区域过去约50年的年度至近年度积累测量数据集。通过验证被动微波信号的时序变化与积累量时序变化的相关性，可评估被动微波遥感技术在未来数十年间监测冰盖积累速率的应用价值。本项目将推动教学、培训与学习工作，并通过参与NASA“冬季历史”项目与热年代学任务（Thermochron Mission），为K-12阶段教师提供美国本土积雪积累与温度监测培训，将极地研究与学生的日常环境相联结，提升代表性不足群体的参与度。本项目将培训本科生与研究生参与极地研究，并鼓励青年研究者投身科研事业。具体而言，将有2名大学生研究经验项目（Research Experiences for Undergraduates, REU）学生参与原创性研究工作，从假说构建到成果展示与发表均纳入本项目范畴。此外，资助一位新锐女性科学家将有助于提升极地研究领域的性别多样性。