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隆升速度的准确性的缺乏，来减少与测量南极洲西部冰块变化有关的不确定性。西南极冰盖(WAIS)的冰损失目前约占当今全球海平面上升的10%。此外，这一地区的冰层正在加速融化。目前，对WAIS演变的准确预测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和测高，卫星重力测量确定了由于地表质量重新分布而导致的地球重力场的变化，测高测量测量了冰面高度的变化。至关重要的是，这两种技术都容易受到误差的影响，这些误差是通过修正固体地球对过去冰川质量损失的隆起反应而引入的，这一过程被称为冰川均衡调整(GIA)。GIA模型需要与区域冰川消融历史和固体地球的流变性有关的信息。在大多数GIA模型中，只考虑了地球结构的一维全球平均值，这是一种严重的过于简单化。我们建议通过新的被动地震学实验来确定(I)西南极和南极半岛的三维地球结构，以及(Ii)通过扩展由NERC资助的半岛GPS网络和新的空间扩展的卫星雷达干涉数据(InSAR)来确定现今的隆升速率。我们将部署10台宽带地震仪，为期2年，与同期的2年POLENET部署相邻，通过确定深至400公里的S波速度-深度模型来估计地球流变学的三维变化。西南极南部南极半岛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理解。我们提出了为期3年的PDRA来开展野外工作和地震研究。地表形变测量的长时间序列对于我们理解GIA的隆升速率是很重要的。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个全球定位系统站点组成的网络。以较小的额外财务成本，但具有显著的科学效益，我们建议将该网络再运营两年。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 Whitehouse联谊会工作的补充；一项为期1.5年的PDRA将结合GIA和形变结果，以更紧密地约束南极半岛南部和西南极过去和现在的冰块变化。虽然全球定位系统的稀疏网络将在大范围内限制形变模式，但我们预计由于当今冰块质量的变化，形变中的波长变化较小。因此，我们计划将卫星雷达干涉测量(InSAR)应用于南极洲西部露头的岩石，以增加变形场的空间采样数量级。由于岩石露头之间的距离可能很大，因此必须从天气模型估计干涉处理过程中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部署6个全球定位系统的当地实地部署来检验这些假设。这一赠款提议的时机至关重要，因为1)在该地区南部资助的为期2年的iStar计划的BAS后勤已经到位；2)美国POLENET地震仪将暂时部署在南部，显著扩大我们的测站覆盖范围；3)支持全球定位系统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.