Defining models of glacial isostatic adjustment in West Antarctica and Antarctic Peninsula (UKANET): better constraints on Earth structure and uplift

我们的目标是通过解决我们对地球结构和现今抬升速率准确性的缺乏了解来减少与南极洲西部冰量变化测量相关的不确定性。目前，南极西部冰盖（WAIS）的冰损失约占当今全球海平面上升的10%。此外，这一地区的冰正在加速流失。对WAIS演变的准确预测目前受到当今冰量变化测量的不确定性的阻碍。得出这种变化的两个关键方法是卫星重力测量法和测高法，卫星重力测量法确定由于表面质量重新分布而引起的地球重力场的变化，测高法测量冰面高度的变化。至关重要的是，这两种技术都容易受到误差的影响，这些误差是通过校正固体地球对过去冰质量损失的抬升响应而引入的，这一过程被称为冰川均衡调整（GIA）。GIA模型需要有关区域冰川消退历史和固体地球流变特性的信息。在大多数GIA模型中，只有1D的全球平均地球结构考虑，这是一个毛oversimplification.我们建议确定（一）三维地球结构在南极洲西部和南极半岛通过一个新的被动地震实验和（ii）现今的隆起率通过扩展的NERC资助的GPS网络在半岛和新的空间广泛的卫星雷达干涉测量数据（干涉合成孔径雷达）。我们将部署10个宽带地震仪2年，邻近同期的2年POLENET部署，通过确定S波速度-深度模型估计地球流变学的三维变化，深度为400公里。西南极洲南部的南极半岛地区从未采集过地震资料，因此对其地球结构了解甚少。岩石圈结构的确定也将提高我们对该地区构造演化的认识。我们建议一个为期3年的PDRA进行实地考察和地震学研究。长时间序列的地表形变测量对于我们理解GIA引起的抬升速率是很重要的。自2009年以来，根据现已终止的NERC/AFI赠款，在南极半岛南部部署了一个由10个GPS站点组成的网络。我们建议再运行该网络2年，这只需要少量额外的财务费用，但会带来重大的科学效益。我们的项目合作伙伴Matt King（塔斯马尼亚大学）将监督这些数据的处理。地震结构结果将被纳入3D GIA模型，作为CI怀特豪斯奖学金工作的补充;为期1.5年的PDRA将联合收割机结合GIA和变形结果，以更严格地约束南极半岛南部和南极西部过去和现在的冰量变化。虽然GPS的稀疏网络将在广泛的范围内限制变形模式，但我们预计由于现今冰量的变化，变形的波长变化较小。因此，我们计划将卫星雷达干涉测量（干涉合成孔径雷达）应用于西南极洲的岩石露头，以增加几个数量级的变形场的空间采样。由于岩石露头之间的距离可能很大，在干涉处理期间对流层雷达传播延迟的空间变化必须根据天气模型进行估计。我们建议在南极半岛当地实地部署6个全球定位系统来检验这些假设。这一赠款建议的时机至关重要，因为：1）BAS后勤工作已经到位，用于该地区南部为期2年的iStar计划; 2）美国POLENET地震仪将暂时定位在南部，大大扩大我们的台站覆盖范围; 3）支持GPS网络的赠款即将结束。

We aim to decrease the uncertainty associated with the measurement of ice mass change in West Antarctica by addressing our lack of knowledge of Earth structure and accuracy of present-day uplift rates. Ice loss from the West Antarctic Ice Sheet (WAIS) currently accounts for around 10% of present-day global sea-level rise. Moreover, this region is undergoing accelerated ice loss. Accurate projections for the evolution of WAIS are currently hindered by uncertainties in measurements of present-day ice mass change. Two key methods for deriving this change are satellite gravimetry, which determines changes in Earth's gravity field due to surface mass redistribution, and altimetry, which measures modifications to the height of the ice surface. Crucially, both of these techniques are susceptible to errors introduced by correcting for the uplift response of the solid Earth to past ice mass loss, a process known as Glacial Isostatic Adjustment (GIA). GIA models require information relating to the regional deglaciation history and the rheological properties of the solid Earth. In most GIA models only 1D global averages of Earth structure are taken in to account; this is a gross oversimplification.We propose to determine (i) 3D Earth structure in West Antarctica and Antarctic Peninsula through a new passive seismological experiment and (ii) present-day uplift rates through the extension of a NERC-funded GPS network in the Peninsula and new spatially extensive satellite radar interferometry data (InSAR). We will deploy 10 broadband seismometers for 2 years, adjacent to a contemporaneous 2 year POLENET deployment, to estimate 3D variations in Earth rheology by determining S-wave velocity-depth models down to depths of 400 km. Seismic data have never been collected in the southern Antarctic Peninsula region of West Antarctica, and hence very little is known about its Earth structure. The determination of lithospheric structure will also improve our understanding of the tectonic evolution of the region. We propose a 3 year PDRA to carry out the fieldwork and seismological research. Long time series of surface deformation measurements are important to our understanding of uplift rates due to GIA. A network of 10 GPS sites has been deployed in the southern Antarctic Peninsula since 2009 under a now terminating NERC/AFI grant. At minor additional financial cost, but with significant scientific benefit, we propose to operate this network for a further 2 years. Our Project Partner Matt King (University of Tasmania) will oversee the processing of these data. The seismic structure results will be incorporated into a 3D GIA model as an addition to CI Whitehouse's Fellowship work; a 1.5 year PDRA will combine the GIA and deformation results to more tightly constrain past and present ice mass change in the southern Antarctic Peninsula and West Antarctica. While the sparse network of GPS will constrain the deformation pattern on a broad scale, we expect smaller wavelength variability in deformation due to present-day ice mass change. Therefore, we plan to apply satellite radar interferometry (InSAR) to the rock outcrops in West Antarctica to increase the spatial sampling of the deformation field by orders of magnitude. Because distances between rock outcrops can be large, the spatial variability of the tropospheric radar propagation delay during interferometric processing has to be estimated from weather models. We propose to test these assumptions with a local field deployment of 6 GPS in the Antarctic Peninsula.The timing of this grant proposal is critical as 1) BAS logistics are already in place for the funded 2 year iStar programme in the south of the region; 2) US POLENET seismometers will temporarily be positioned to the south and significantly extend our station coverage; 3) the grant supporting the GPS network is ending.