Measuring Antarctic uplift due to ice loss, from space

这个令人兴奋的项目将使用从太空进行的地面运动测量，以限制地面对南极当前和过去冰块变化的反应。这反过来将改善对正在进行的冰川融化的估计。这名学生将常驻利兹，并将在南极进行可选的实地考察。西南极冰盖的冰损失已经占到了当今全球海平面上升的10%左右，而且还在加速。当冰的质量发生变化时，下面的地面对地表负荷的变化既有立即的反应，也有长达数千年的延迟反应，这种效应被称为冰川均衡调整(GIA)。了解GIA的响应是限制正在进行的冰流失的关键，因为它也影响到用于限制正在进行的冰流失的主要测量方法：卫星重力和校时仪。GIA的响应取决于地幔的流动特性(流变性)，这些特性在垂直和横向上都是可变的，而且鲜为人知。我们确实受到的这些限制来自地震研究，也来自全球导航卫星系统对地面运动测量进行的粘弹性建模(例如，Nfield等人，2014年；Samrat等人，2020年)。然而，在如此恶劣和偏远的位置运行全球导航卫星系统仪器所面临的后勤挑战意味着，测量结果在空间上是稀疏的，并且不能捕捉到地面位移的全部变异性，因为各个冰川对变化的条件作出不同的反应。在南极进行这些测量是具有挑战性的，因为冬季的积雪和大片区域被冰覆盖，但我们的初步努力表明这是可能的。InSAR通常用于自然灾害社区的地震分析和火山监测，在利兹大学，我们开发了大量数据处理的算法，并减少了由多变的大气条件引入的测量误差。InSAR还被用于商业应用，如监测基础设施，SatSense Ltd开发了他们自己的最先进的InSAR处理和解释方法。该项目的目的是利用利兹和SatSense的综合专业知识在整个南极半岛进行InSAR测量，并与BAS和Durham的专家合作，使用这些数据通过建模更好地约束该地区的流变特性。该项目还将涉及在南极半岛的关键地点安装雷达反射器的实地工作，前提是成功申请BAS的支持。具体目标是：处理整个南极半岛的InSAR数据，并提取单个岩石露头的时间序列；将最新的大气校正技术应用于InSAR数据；在半岛上安装雷达反射器，以提供对速度的绝对约束；将InSAR测量与GNSS数据结合使用，以约束粘弹性模型。合成孔径雷达干涉测量地壳形变时间序列分析的最新进展。《构造物理学》，第514页，第1-13页。2014年。南极半岛基岩的快速抬升可用粘弹性对近期冰卸载的响应来解释。《地球与行星科学通讯》，397，32-41。Samrat，Nahidul Hoque，等人。从GPS推断的南极半岛北部冰质量减少和三维粘弹性形变

This exciting project will use measurements of ground movement made from space, to constrain the response of the ground to current, and past, ice mass change in the Antarctic. This in turn will improve estimates of ongoing ice loss. The student will be based in Leeds and optional fieldwork in the Antarctic will be involved.Ice loss from the West Antarctic Ice Sheet already accounts for around 10% of present-day global sea-level rise and is accelerating. As the mass of the ice changes, the ground beneath responds to the change in surface loading both immediately, and with a delayed response lasting up to thousands of years, an effect known as glacial isostatic adjustment (GIA). Understanding the GIA response is key to constraining ongoing ice loss, as it also affects the main measurement methods used to constrain ongoing ice loss: satellite gravimetry and altimetry.The GIA response depends on the flow characteristics (rheology) of the mantle, which are vertically and laterally variable, and poorly known. Those constraints we do have come from seismic studies and also from viscoelastic modelling of ground motion measurements made by GNSS (e.g. Nield et al, 2014; Samrat et al, 2020). However, the logistical challenge of running GNSS instruments in such a hostile and remote location means that the measurements are spatially sparse, and are not able to capture the full variability of ground displacements, as individual glaciers respond differently to changing conditions.Radar Interferometry (InSAR), on the other hand, is a technique that can provide spatially dense measurements of surface displacement from space (Hooper et al, 2012). Making these measurements in the Antarctic is challenging, due to snow coverage in winter and with large regions covered by ice, but our preliminary efforts have shown it to be possible.InSAR is commonly used in the natural hazards community for earthquake analysis and monitoring of volcanoes, and at the University of Leeds we have developed algorithms for mass processing of data, and the reduction of measurement errors introduced by variable atmospheric conditions. InSAR is also used for commercial applications, such as monitoring of infrastructure, and SatSense Ltd have developed their own state-of-the-art approach to InSAR processing and interpretation.The aim of this project is to use the combined expertise from Leeds and SatSense to make InSAR measurements over the whole Antarctic Peninsula and, working with experts in BAS and Durham, to use these data to better constrain the rheological properties of the region through modelling. The project will also involve fieldwork to install radar reflectors at key locations on the Antarctic Peninsula, subject to a successful application for support from BAS. This will enable the InSAR results, which are relative measurements, to be tied to a global reference frame.Specific objectives are:Process InSAR data for the whole Antarctic Peninsula and extract time series for individual rocky outcrops;Apply the latest atmospheric correction techniques to the InSAR data;Install radar reflectors on the peninsula to provide absolute constraints on velocity;Use the InSAR measurements combined with GNSS data to constrain viscoelastic models.ReferencesHooper, A., Bekaert, D., Spaans, K. and Arikan, M., 2012. Recent advances in SAR interferometry time series analysis for measuring crustal deformation. Tectonophysics, 514, pp.1-13.Nield, G. A., et al. 2014. Rapid bedrock uplift in the Antarctic Peninsula explained by viscoelastic response to recent ice unloading. Earth and Planetary Science Letters, 397, 32-41.Samrat, Nahidul Hoque, et al. "Reduced ice mass loss and three-dimensional viscoelastic deformation in northern Antarctic Peninsula inferred from GPS