Ice and Fire: Investigating Links between Mantle Dynamics and Ice Sheet Stability

南极西部和格陵兰冰盖正在以越来越快的速度失去质量，如果温室气体排放继续有增无减，预计到2100年，海平面将上升0.5至1.8米。这些预测对沿海人口具有巨大的经济和人道主义影响，约有10亿人生活在预计将被风暴潮永久淹没或定期淹没的地区。然而，未来海平面变化的速率、幅度和空间分布仍然高度不确定，这在很大程度上是由于在人类和地质时间尺度上对极地冰量变化和固体地球变形之间的相互作用缺乏约束。该项目旨在填补这一知识空白，方法是将先进的数值建模技术与新的地球物理和地质数据集相结合，以量化不断演变的地幔动力学对过去、现在和未来冰盖稳定性的贡献，地幔动力学可以通过几个重要方式影响冰盖稳定性：地幔对流驱动的地表隆起和下沉可以改变主要冰川的接地线位置;上涌地幔柱可增加流入冰盖底部的热流，引发融化并增加冰流速度;温度升高可降低地幔粘度，加速冰川均衡调整以应对冰量变化。这些不同影响的准确量化仍然具有挑战性，但由于最近的进展，现在已经成为可能。首先，地震成像技术的改进大大提高了我们对地幔三维速度结构的认识。第二，现代岩石力学实验使将地震速度映射到关键的物理性质，如温度、密度和粘度成为可能。第三，最近开发了一种先进的软件，可以精确模拟具有显著横向粘度变化的地球中的地幔对流和冰川均衡调整。最后，地球物理和地质数据集的快速增长，特别是在极地地区，使数值模型输出的基准比以前更严格。 该项目旨在利用地球科学领域的这些突破，主要目标包括但不限于：（一）建立地球内部温度、密度和粘度结构的精确三维模型; ii）用这些修订的地球模型量化对流支持的垂直运动和冰川均衡调整，以评估过去温暖时期的海平面（如上新世中期温暖期和末次间冰期）及其对现代海平面上升的影响; iii）确定更新的粘度结构对现有极地冰质量损失测量的影响。

The West Antarctic and Greenland ice sheets are losing mass at increasingly rapid rates and are projected to contribute between 0.5 and 1.8 m of sea-level rise by 2100 if greenhouse gas emissions continue unabated. These forecasts have huge economic and humanitarian implications for coastal populations with ~1 billion people living in regions expected to be permanently inundated or regularly flooded by storm surges. However, the rate, magnitude and spatial distribution of future sea-level change remains highly uncertain due, in large part, to poor constraint on the interaction between polar ice mass changes and solid Earth deformation on both human and geological timescales. This project aims to address this knowledge gap by combining advanced numerical modelling techniques with new geophysical and geological datasets to quantify the contribution of evolving mantle dynamics to past, present and future ice sheet stability.Mantle dynamics can influence ice sheet stability in several important ways: mantle convection-driven uplift and subsidence of the Earth's surface can alter the grounding line position of major glaciers ); upwelling mantle plumes can increase heat flow into the base an ice sheet, triggering melting and increasing ice flow velocities ; and elevated temperatures can reduce mantle viscosity, accelerating glacial isostatic adjustment in response to ice mass changes. Accurate quantification of these different effects remains challenging but is now possible thanks to recent advances. First, improvements in seismic imaging have greatly enhanced our knowledge of the threedimensional velocity structure of the mantle. Secondly, modern rock mechanics experiments have made it possible to map seismic velocities into key physical properties, like temperature, density and viscosity. Thirdly, sophisticated software that can accurately model mantle convection and glacial isostatic adjustment in an Earth with significant lateral viscosity variations has recently been developed. Finally, the rapid growth of geophysical and geological datasets, especially in the polar regions, allows numerical model outputs to be benchmarked far more stringently than was previously possible. This project aims to leverage these breakthroughs from across the geosciences, with major objectives including, but not limited to: i) creation of accurate three-dimensional models of Earth's internal temperature, density and viscosity structure; ii) quantification of convectivelysupported vertical motions and glacial isostatic adjustment with these revised Earth models to evaluate sea-levels during past warm periods (e.g. Mid-Pliocene Warm Period and Last Interglacial) and their implications for modern sea-level rise; iii) determination of the impact of updated viscosity structure on existing measurements of ice mass loss from the poles.