Quantifying West Antarctic mantle viscosity via precise GPS measurement of Earth's response to surface mass balance anomalies

冰盖变化的卫星测量对于了解和帮助预测海平面上升是必要的，但被称为冰川均衡调整（GIA）的现象所污染。GIA是一种持续的固体地球变形形式，以响应先前的冰盖质量变化。原则上，只要我们能接触到基岩，就可以测量它，但南极大部分地区的情况并非如此，因此（也是出于实用性的原因）我们需要基于物理的GIA数学模型。必须对这些模型进行校准和验证，这可以借助安放在基岩上的连续全球定位系统接收器对地球变形进行的精确测量来完成，因此，连续的全球定位系统数据对于确定南极洲过去和现在的冰量变化以及量化冰动力学和固体地球变形之间的反馈至关重要。在这种研究中必须量化的一个基本性质是固体地球的流变学（其对作用于其上的力的变形反应）。地幔在较长的时间尺度上表现出粘性行为，但在短期内表现出弹性行为（如通过地震波的通过所观察到的），这种现象称为粘弹性。最近的研究表明，整个南极洲的地幔粘度存在很大的空间变化，但目前尚不清楚这种变化的幅度。我们建议开拓一种新的方法来确定空间可变的地幔粘度，包括分析固体地球的粘弹性响应，情节表面质量平衡（SMB）异常整个南极洲。我们的方法利用这样一个事实，即在地区的表面质量变化的幅度是众所周知的，伴随着固体地球响应的观测允许量化的流变学性质的地球。为了实现我们的目标，我们需要访问高精度，长时间的GPS记录。幸运的是，在南极洲西部已经有了一个广泛的GPS网络，虽然通过一系列NERC资助的项目（以及同等的海外赠款）建立了一个零碎的网络，但现在有可能在未来几年内提供这样的记录。因此，我们建议彻底改革属于联合王国在南极后勤支助范围内的现有全球定位系统网络;我们将在现有地点的一个战略子集延长时间序列，并通过卫星将所有数据传输到开放访问服务器。由此产生的精度和数据可访问性的阶跃变化将使我们能够实现我们的科学目标，同时将使国际科学界受益：为西南极洲提供开放获取的GPS时间序列将有助于新兴的数据反演活动，并使数百万美元的重力恢复和气候实验（GRACE）提供的地面实况冰质量平衡估计成为可能。执行使命，定于2017年发射。

Satellite measurements of ice sheet change are necessary to understand and help predict sea level rise, but are contaminated by a phenomenon known as Glacial Isostatic Adjustment (GIA). GIA is a form of ongoing solid Earth deformation in response to previous ice sheet mass changes. It can in principle be measured wherever we have access to bedrock, but this is not the case for much of Antarctica and therefore (and also for reasons of practicability) we require physically-based mathematical models of GIA. These models must be calibrated and validated, which can be done with the aid of precise measurements of Earth deformation made using continuous GPS receivers sited on bedrock.Continuous GPS data are therefore crucial to the determination of past and present ice mass change across Antarctica and the quantification of feedbacks between ice dynamics and solid Earth deformation. A fundamental property that must be quantified in such studies is the rheology of the solid Earth (its deformational response to forces acting on it). The Earth's mantle shows viscous behaviour over longer timescales but behaves elastically in the short term (as observed e.g. by the passage of seismic waves), a phenomenon known as viscoelasticity. Recent studies have demonstrated that there are large spatial variations in mantle viscosity across Antarctica, but at present the magnitude of such variations is not known. We propose to pioneer a new approach to determining spatially-variable mantle viscosity that involves analysing the viscoelastic response of the solid Earth to episodic surface mass balance (SMB) anomalies across Antarctica. Our approach makes use of the fact that in regions where the magnitude of surface mass change is well known, observations of the accompanying solid Earth response allow the quantification of the rheological properties of the Earth.In order to achieve our goal we require access to high-precision, long-duration GPS records. Fortunately there is already an extensive GPS network in West Antarctica, which although erected piecemeal via a series of NERC-funded projects (and equivalent overseas grants), now has the potential to deliver such records over the next few years. We therefore propose to overhaul the existing GPS network that lies within the remit of UK logistical support in Antarctica; we will extend the time series at a strategic subset of the existing sites, and transmit all data to open access servers via satellite. The resulting step change in precision and data accessibility will enable us to achieve our scientific goals and at the same time will benefit the international scientific community: the provision of open access GPS time series for West Antarctica will contribute to emerging data inversion activities and make it possible to ground-truth ice mass balance estimates delivered by the multi-million-dollar Gravity Recovery and Climate Experiment (GRACE) Follow-on mission, which is due for launch in 2017.