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当今上升速度准确性缺乏了解的问题，减少与南极洲西部冰质量变化测量相关的不确定性。南极西部冰盖（WAIS）的冰损失目前占全球海平面上升的10%左右。此外，该地区正在经历加速的冰损失。对WAIS演变的准确预估目前受到当今冰质量变化测量的不确定性的阻碍。获得这种变化的两种关键方法是卫星重力场法和测高法。卫星重力场法测定地表质量再分配引起的地球重力场变化，卫星重力场法测量冰层表面高度的变化。至关重要的是，这两种技术都容易受到校正固体地球对过去冰质量损失的隆起响应所带来的误差的影响，这一过程被称为冰川均衡调整（GIA）。GIA模式需要与区域消冰历史和固体地球流变特性有关的信息。在大多数GIA模型中，只考虑地球结构的一维全球平均值；这是一种过于简单化的说法。我们建议通过一项新的被动地震学实验来确定(i)南极洲西部和南极半岛的三维地球结构；（ii）通过在半岛上扩展nerc资助的GPS网络和新的空间广泛的卫星雷达干涉测量数据（InSAR）来确定当今的隆升率。我们将部署10个宽带地震仪，为期2年，与POLENET同时部署2年，通过确定深度为400公里的s波速度-深度模型来估计地球流变学的3D变化。在南极洲西部的南极半岛南部地区从未收集过地震数据，因此对其地球结构知之甚少。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。我们建议进行为期3年的实地调查和地震研究。长时间序列的地表变形测量对于我们理解由于GIA引起的隆起率是很重要的。自2009年以来，在现已终止的NERC/AFI资助下，在南极半岛南部部署了一个由10个GPS站点组成的网络。我们建议将该网络再运营2年，增加的财政成本较小，但具有显著的科学效益。我们的项目合作伙伴马特·金（塔斯马尼亚大学）将监督这些数据的处理。地震结构的结果将被纳入一个3D GIA模型，作为CI Whitehouse奖学金工作的补充；为期1.5年的PDRA将结合GIA和变形结果，更严格地约束南极半岛南部和南极洲西部过去和现在的冰块变化。虽然GPS稀疏网络将在大范围内限制变形模式，但我们预计由于当前冰质量变化而导致的变形的波长变异性较小。因此，我们计划将卫星雷达干涉测量技术（InSAR）应用于西南极洲的岩石露头，以增加变形场的空间采样数个数量级。由于岩石露头之间的距离可能很大，因此必须根据天气模式估计干涉处理期间对流层雷达传播延迟的空间变异性。我们建议通过在南极半岛局部部署6个GPS来测试这些假设。这项赠款提案的时机至关重要，因为1)BAS已经为该地区南部资助的2年iStar计划提供了后勤保障；2)美国POLENET地震仪将暂时放置在南方，大大扩大我们台站的覆盖范围；3)支持GPS网络的拨款即将结束。

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.