Totten Glacier Active and Passive Source Experiment

The Totten Glacier (TG) system drains 10% of the East Antarctic Ice Sheet [Rignot and Thomas, 2002], with enough ice to cause global sea level to rise by 6 m [Roberts et al., 2011]. TG has undergone substantial modulation of both flow and ice thickness since 1989 [Li et al. 2016], with retreat of the grounding line observed since 1996 [Li et al. 2015]; however, the origins of the changes remain poorly understood. This uncertainty hampers the reliable quantification of future risk due to the fact that only a few days of fieldwork have been undertaken on the glacier in the last four decades. We aim to improve our understanding of ice-ocean interactions and the mass balance of the TG system through acquiring new ground-based data across the ice shelf and grounding zone region, and also reoccupying nearby historic geophysical sites [Allen and Whitworth, 1970]. In particular, we aim to undertake simultaneous measurements of ice shelf basal melting and velocity, as well as map firn depth-density, basal geometry, subglacial conditions and reoccupy geophysical sites from the 1960s to quantify both current and long-term changes in the glacier system. The specific objectives of this research are to: 1. Measure basal melt (or freeze-on) and firn compaction (or thickening), and determine the degree of ice-ocean interactions beneath the ice shelf using autonomous phase-sensitive radar (ApRES) at a series of locations on the ice shelf and grounded ice to evaluate ice-shelf/ocean models of the region 2. Determine the tidal influence on ice dynamics, capture ice flow velocities and determine the limits of where the ice shelf is in isostatic equilibrium in the grounding zone region 3. Map the geometry of the ocean cavity, capture ocean stratification and map firn densification through the use of active seismic across the ice shelf 4. Characterise the subglacial environment and its role in ice dynamics through the use if active seismic data along the grounding zone region of TG.

托滕冰川（Totten Glacier, TG）系统承担了南极东冰盖10%的冰体排泄任务[Rignot与Thomas, 2002]，其蕴含的冰量足以使全球海平面上升6米[Roberts等人, 2011]。自1989年以来，托滕冰川的流速与冰厚均发生了显著变化[Li等人, 2016]，且1996年起观测到其接地线出现退缩现象[Li等人, 2015]；但目前学界对这类变化的成因仍知之甚少。这种不确定性阻碍了未来风险的可靠量化——因为在过去四十年间，针对该冰川开展的野外实地工作仅寥寥数日。本研究旨在通过在冰架与接地线区域获取新的地面观测数据，并重测附近的历史地球物理观测测点[Allen与Whitworth, 1970]，以加深对托滕冰川系统冰-海相互作用与物质平衡的理解。具体而言，本研究计划同步开展冰架底部融化与流速的测量，同时绘制粒雪层深度-密度分布、冰架底部几何形态与冰下环境分布图，并重测20世纪60年代的地球物理观测测点，以量化该冰川系统当前与长期的变化。本研究的具体目标如下：
1. 在冰架与接地冰的一系列测点处部署自主相敏雷达（Autonomous Phase-sensitive Radar, ApRES），测量冰架底部的融冰（或冻结）过程与粒雪压实（或增厚）情况，以此评估本区域的冰架-海洋模型，量化冰架下方的冰-海相互作用程度；
2. 确定潮汐对冰体动力学的影响，获取冰流流速数据，并明确接地线区域内冰架处于等静压平衡的范围；
3. 通过在冰架上开展主动地震勘探，绘制海洋空腔几何形态、获取海洋层结数据，并完成粒雪致密化过程的测绘；
4. 通过在托滕冰川接地线区域采集主动地震数据，刻画冰下环境特征及其在冰体动力学中的作用。