EAR - Climate; Investigating Effects of 3-Dimensional and Non-Newtonian Mantle Viscosity on Relative Sea-Level Changes and Deglaciation History Since the Last Glacial Maximum

EAR——气候；

• 批准号: 2222115
• 负责人: Shijie Zhong
• 金额: $ 36.61万
• 依托单位: University of Colorado at Boulder
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2022
• 资助国家: 美国
• 起止时间: 2022-09-01 至 2025-08-31
• 项目状态: 未结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=2222115&HistoricalAwards=false
• 关键词: EAR; Climate; Investigating; Effects; Dimensional

Some 26,000 years ago, much of North America and Europe was covered by ice sheets several kilometers thick. These ice sheets started to melt and by about 8,000 years ago they were mostly gone, but their meltwater caused the sea level to rise globally by about 130 meters. As the ice sheets melted, the land that used to support them gradually rose in response, while the vast ocean floors subsided under the load of added weight from the meltwater. This slow rising and falling of the Earth’s surface in response to deglaciation is called glacial isostatic adjustment (GIA). GIA tells us about sea-level change and ice sheet melting history, as well as flow in the Earth's mantle and even rotation of the Earth, but it is a huge topic requiring the effort of many scientists and highly sophisticated computational models. To make this effort more efficient, Dr. Zhong will be updating his software (CitcomSVE) and sharing it freely with other researchers. Dr. Zhong's own research group will address uncertainties in deglaciation history for the last 26,000 years, and seek to resolve conflicting modeling results from previous studies. If he is successful, his software can be used with confidence to project sea level change in the near future. This will help scientists, engineers and other stakeholders understand risks associated with sea level rise and take steps to improve resilience in the highest-risk coastal regions. GIA studies determine mantle viscosity and construct deglaciation history for the last ~26,000 years since the last glacial maximum (LGM). However, the two widely used ICE6G [Peltier et al., 2015] and ANU [Lambeck et al., 2017] ice models differ significantly, and so do their accompanying mantle viscosity models. Furthermore, while various studies of rock deformation including laboratory experiments and geodynamic modeling indicate that mantle viscosity is temperature- and stress-dependent (i.e., non-Newtonian) [e.g., Karato, 2008], observational evidence for the influence of non-Newtonian viscosity in GIA process remains elusive. This project has three objectives: 1) to construct an improved ice model and mantle viscosity model that explains the combined relative sea level (RSL) datasets used by the Peltier and Lambeck groups, 2) to seek observational evidence in GIA process for non-Newtonian mantle in quasi-L shaped RSL curves from locations near former ice sheet edges, and 3) to develop a publicly available finite element package CitcomSVE for modeling GIA and tidal deformation problems. This project consists of the following three tasks to accomplish these objectives. Task 1 is to further develop the newly upgraded, open-source package, CitcomSVE code, by including more efficient computational methods for solving Earth’s gravitational field and physically more realistic features such as mantle compressibility. Task 2 is to further analyze the RSL data considered by Peltier and Lambeck groups, to seek ice models and 1-D mantle viscosity models that better explain these RSL data at near-field and far-field sites and GRACE data, and to test the effects of 3-D mantle viscosity derived from seismic models and plate boundary viscosity on GIA observables. Task 3 is to examine the effects of non-Newtonian viscosity on simulations of the GIA process, to characterize the quasi-L shaped RSL curves at near-field sites, to understand causes of the quasi-L-shaped RSL curves in terms of deglaciation history and non-Newtonian viscosity, and to test the hypothesis that the effect of non-Newtonian viscosity is evident in the RSL observations.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.

大约26，000年前，北美和欧洲的大部分地区都被冰盖覆盖了几公里。这些冰片开始融化，大约8000年前它们大部分都消失了，但是它们的融水导致全球海平面上升约130米。随着冰盖的融化，用来支撑它们的土地逐渐响应，而巨大的海板在融合水的额外重量下逐渐消失。响应脱气的这种缓慢上升和地球表面的下降称为冰川等静态调节（GIA）。 GIA告诉我们有关海平面变化和冰盖熔化历史的信息，以及地球地幔甚至旋转的流动，但这是一个巨大的话题，需要许多科学家和高度复杂的计算模型的努力。为了使这项努力更加高效，郑博士将更新他的软件（Citcomsve），并与其他研究人员免费分享。钟博士自己的研究小组将在过去26，000年中解决脱气历史的不确定性，并寻求解决以前研究的矛盾建模结果。如果他成功，他的软件可以充满信心地在不久的将来投射海平面变化。这将帮助科学家，工程师和其他利益相关者了解与海平面上升相关的风险，并采取措施提高最高风险的沿海地区的弹性。 GIA研究确定了自上次冰川最大值（LGM）以来的最后26，000年的地幔粘度和构建脱气病史。然而，两种冰的使用ICE6G [Peltier等，2015]和Anu [Lambeck等，2017]冰模型的差异很大，其参与的地幔粘度模型也是如此。此外，尽管包括实验室实验和地球动力学建模的岩石变形研究各种研究表明，地幔粘度是温度和压力依赖性的（即非牛顿）[例如，Karato，2008]，《观察证据》，对于非纽顿粘度在GIA过程中的影响仍然难以捉摸。该项目具有三个目标：1）构建改进的冰模型和地幔粘度模型，该模型解释了Peltier和Lambeck组使用的相对海平面（RSL）数据集，2）在GIA过程中寻求观察性证据，用于在Quasi-lape for for offient for i <newtonian cite e元素的元素中，以及3型元素的元素曲线，以及3），以及3）。和潮汐变形问题。该项目包括以下三个任务来实现这些目标。任务1是通过包括更有效的计算方法来求解地球引力场和物理上更现实的功能，例如地幔兼容性，以进一步开发新升级的开源软件包Citcomsve代码。任务2是要进一步分析Peltier和Lambeck组考虑的RSL数据，以寻求冰模型和1-D地幔粘度模型，以更好地解释这些RSL数据，这些RSL数据在近场和远场站点和宽限期数据上，并测试从地震模型和板界粘度对GIA观察的3-D地幔粘度的影响。任务3是要检查非牛顿粘度对GIA过程模拟的影响，以表征近场位点上的准形状RSL曲线，以了解准L形曲线的原因，以脱发历史和非纽顿粘度和非纳维顿粘度，并测试非纽约人的效应，以证明其效应是非纽顿的效应。 NSF的法定使命，并使用基金会的知识分子优点和更广泛的审查标准来评估，被认为是宝贵的支持。