Seasonal flow variability as an indicator of mountain glacier basal conditions

季节性流量变化作为山地冰川基础条件的指标

• 批准号: 2604193
• 金额: --
• 依托单位: University of Leeds
• 依托单位国家: 英国
• 项目类别: Studentship
• 财政年份: 2021
• 资助国家: 英国
• 起止时间: 2021 至 无数据
• 项目状态: 未结题
• 来源: https://gtr.ukri.org/projects?ref=studentship-2604193
• 关键词: Seasonal; flow; variability; indicator; mountain

Seasonal flow variability as an indicator of mountain glacier basal conditionsLead supervisor: Duncan Quincey (University of Leeds)Co-supervisors: Francesca Pellicciotti (WSL), John Elliott (Leeds), Noel Gourmelen (Edinburgh)Glacier thermal regime, and in particular the presence or absence of meltwater at the bed, is a key control of subglacial processes. It governs rates of sediment erosion, entrainment and transport1, the nature of subsurface hydrological networks2, and patterns and rates of glacier flow3. Evidence suggests that rising air temperatures are influencing englacial and subglacial thermal conditions even at high-altitude4, meaning that in a future warming world polythermal and temperate ice conditions will become more widespread. Being able to characterise glacier basal conditions, and how they change, will therefore be critical for predicting landscape evolution, meltwater storage and conveyance, glacier discharge, and ultimately for forecasting glacier decay.Given that direct observations of subglacial conditions are limited to localised exposures or speleological investigations5, a remote sensing approach that serves as a proxy for subglacial water storage would be a useful tool for mountain glaciologists. Previous work2,3 has suggested that seasonal changes in glacier velocity can indicate subglacial water storage, associated with glacier sliding, and therefore temperate ice (Figure 1).Figure 1: The Baltoro Glacier, Karakoram (left), and its annually averaged centreline velocity. Seasonal velocities (right) indicating warm ice at higher elevations as the profiles diverge at ~10 km from the terminus.This PhD project will therefore seek to test and expand this hypothesis, by initially deriving seasonal velocity data for mountain glaciers with known thermal characteristics, to describe spatial patterns of flow, and their change through time. It will build on previous work from within the supervisory group, primarily making use of image feature tracking and radar interferometry for bespoke velocity analyses, supplemented by freely available datasets from existing repositories such as ITS_LIVE. It will explore a range of space-based SAR (e.g. Sentinel-1) and optical (e.g. Planet) imagery, as well as off-the-shelf and custom-built digital elevation datasets, and will develop existing and derive new routines for automating processing workflows. Subsequent steps will assimilate regional datasets of speed-up/slow-down, supported by modelled climate, ice thickness and energy balance data, to infer broader subglacial conditions. There is also the opportunity to collect complementary field-based velocity data, using micro-dgps, depending on the interests/skills of the successful applicant.ReferencesCook et al., (2020) 10.1038/s41467-020-14583-8. 2. Benn et al., (2017) 10.5194/tc-11-2247-2017. 3. Quincey et al., (2009) 10.3189/002214309790794913. 4. Vincent, C. et al., (2020) 10.5194/tc-14-925-2020. 5. Temminghoff et al., (2018) 10.1080/04353676.2018.1545120.

季节性流动变化作为山区冰川基础条件的指标首席主管：邓肯昆西（利兹大学）共同主管：弗朗西斯卡佩利乔蒂（WSL），约翰埃利奥特（利兹），诺埃尔古梅伦（爱丁堡）冰川热状况，特别是在床融水的存在或不存在，是冰下过程的关键控制。它控制着沉积物侵蚀、夹带和运输的速率1，地下水文网络的性质2，以及冰川流动的模式和速率3。有证据表明，即使在高海拔地区，气温上升也在影响冰内和冰下的热条件，这意味着在未来变暖的世界中，多温和温带冰条件将变得更加普遍。因此，能够了解冰川基础条件及其变化，对于预测景观演变、融水储存和输送、冰川排放以及最终预测冰川衰退至关重要。鉴于对冰下条件的直接观测仅限于局部暴露或洞穴学调查5，作为冰下水储存替代物的遥感方法将是山区冰川学家的一个有用工具。以前的研究表明，冰川速度的季节性变化可以指示冰下水的储存，与冰川滑动有关，因此是温带冰（图1）。图1：喀喇昆仑巴尔托洛冰川（左）及其年平均中心线速度。季节性流速（右）表明，当剖面在距离终点约10公里处发散时，较高海拔处的暖冰。因此，本博士项目将试图测试和扩展这一假设，通过初步推导具有已知热特征的山地冰川的季节性流速数据，来描述流动的空间模式及其随时间的变化。它将建立在监督小组内部以前的工作基础上，主要利用图像特征跟踪和雷达干涉测量进行定制速度分析，并辅之以ITS_LIVE等现有储存库中免费提供的数据集。它将探索一系列天基合成孔径雷达（如哨兵-1）和光学（如行星）图像，以及现成的和定制的数字高程数据集，并将开发现有的和派生的自动化处理工作流程的新例程。随后的步骤将吸收加速/减速的区域数据集，并得到模拟气候，冰厚度和能量平衡数据的支持，以推断更广泛的冰下条件。根据成功申请人的兴趣/技能，也有机会使用微型差分全球定位系统收集补充的基于场的速度数据。（2020）10.1038/s41467-020-14583-8. 2. Benn等人，（2017）10.5194/tc-11-2247-2017。3. Quincey等人，（2009）10.3189/002214309790794913。4.文森特角例如，（2020）10.5194/tc-14-925-2020。5. Temminghoff等人，（2018）10.1080/04353676.2018.1545120.