Development of a Viscoelastic Ice-flow Model for Process-based Prediction of Ice-Sheet Evolution

开发用于基于过程的冰盖演化预测的粘弹性冰流模型

• 批准号: 0909335
• 负责人: Richard Alley
• 金额: $ 29.51万
• 依托单位: Pennsylvania State Univ University Park
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2009
• 资助国家: 美国
• 起止时间: 2009-09-01 至 2013-08-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0909335&HistoricalAwards=false
• 关键词: Development; Viscoelastic; Ice; flow; Model

This award is funded under the American Recovery and Reinvestment Act of 2009 (Public Law 111-5).Alley 0909335Pennsylvania State UniversityThe glaciology community lacks a quantitatively predictive understanding of sliding and bed deformation. The PIs propose a modeling effort to develop viscoelastic ice-flow models overlying a viscous-plastic bed and associated techniques for data assimilation to help constrain basal flow laws describing this bed. For ice, the Maxwell model (consisting of a spring and dashpot in series) is anticipated to prove sufficient when the standard Newtonian (linear) dashpot is replaced by one obeying Glen's (nonlinear) flow law. The Maxwell model allows instantaneous elastic response, as well as stress relaxation, in which the stress required to sustain a given strain rate in the material diminishes over time. Thus, the Maxwell model is well-suited to materials for which viscous and elastic behavior are relatively independent, so that changing a model from viscous to Maxwell viscoelastic may be viewed as adding an elastic "overlay" to the existing model. Prior success in modeling tidal forcing of a purely elastic ice stream lends support to this approach. However, should the Maxwell model prove inadequate, the PIs are prepared to investigate a Burgers model, which consists of a Maxwell unit in series with a Kelvin unit (itself consisting of a spring and dashpot in parallel). In addition to the viscous and instantaneous elastic behavior of the Maxwell model, the Burgers model also displays delayed elastic response to forcing at certain frequencies. At the longer timescales of interest for glacial flow, though, the PIs expect that any lag between forcing and (nonlocal) response will result from the finite propagation speed of elastic waves. They plan to begin by adding Maxwell viscoelastic behavior to a depth-integrated, width-averaged ice stream-ice shelf model. This type of one-dimensional model allows for relatively straightforward incorporation of new physics, yet is sophisticated enough to assess the effects of ice shelf buttressing and basal melting.

该奖项是根据2009年美国复苏和再投资法案(公法111-5)资助的。宾夕法尼亚州立大学小巷冰川学界缺乏对滑动和河床变形的定量预测理解。PI提出了一种模拟工作，以开发覆盖在粘塑性床上的粘弹性冰流模型和相关的数据同化技术，以帮助约束描述该床的基本流动规律。对于冰，麦克斯韦模型(由弹簧和仪表盘串联组成)被符合格伦(非线性)流动定律的标准牛顿(线性)仪表盘取代时，预计将被证明是足够的。麦克斯韦模型允许瞬时弹性响应以及应力松弛，其中维持材料中给定应变率所需的应力随着时间的推移而减小。因此，Maxwell模型非常适用于粘性和弹性行为相对独立的材料，因此将模型从粘性改为Maxwell粘弹性可以被视为在现有模型的基础上增加了一层弹性“覆盖”。以前在模拟纯弹性冰流的潮汐强迫方面的成功为这种方法提供了支持。然而，如果麦克斯韦模型被证明是不充分的，PI准备研究Burgers模型，该模型由一个串联的Maxwell单元和一个开尔文单元(本身由弹簧和仪表盘并联组成)组成。除了Maxwell模型的粘性和瞬时弹性行为外，Burgers模型还表现出对某些频率的强迫的延迟弹性响应。然而，在冰川流感兴趣的较长时间尺度上，PI预计，强迫和(非局部)响应之间的任何滞后都将由弹性波的有限传播速度造成。他们计划首先将麦克斯韦粘弹性行为添加到深度集成、宽度平均的冰流-冰架模型中。这种类型的一维模型允许相对直截了当地结合新物理，但也足够复杂，可以评估冰架支撑和底部融化的影响。