NSFGEO-NERC: Collaborative Research: Two-Phase Dynamics of Temperate Ice

该奖项支持一个研究温带冰的项目，使用实验方法和建模，以确定水对其流动阻力和结构的影响，并研究冰内水的流动性。结合这些实验，建立了一个新的冰流流动和温度的数学模型。该模型包括变形冰的产水、储水和运动，以及它们对冰流边缘流动阻力和冰流床润滑用水可用性的影响。结果将改进对变暖气候下冰流速度和几何形状演变的估计，从而提高对南极冰盖对下个世纪海平面上升的贡献的评估的准确性。冰流是南极冰盖内快速流动的区域，主要负责向海洋排放冰，并对海平面上升产生重大影响。水在冰流的流动中起着核心作用。它润滑了它们的基础，软化了它们的边缘，在那里流动速度突然从快速转变为缓慢。在冰流的边缘，有些冰是“温和的”，这意味着它处于融化温度，因此含有晶间水，可以显著软化冰。两名博士后研究人员将获得学术生涯的支持、培训和指导，三名本科生将被引入地球科学研究。该奖项是NSF/GEO-UK NERC领导机构机会（NSF 14-118）的一部分，是美国爱荷华州立大学和英国牛津大学之间的合作。将研究温带冰的两阶段变形，目的是确定其对南极冰流流动的影响。该项目有两个相互加强的组成部分。首先将进行实验室实验，使用爱荷华州立大学的旋转装置来确定温带冰的含水量与其流变性和渗透性之间的关系。第二个组成部分将涉及在牛津大学发展温带冰的两相流体动力学理论，并将该理论应用于冰流动力学模型。实验结果将指导理论中考虑的本构规则和参数范围，理论元素的应用将改进对实验结果的解释。理论和由此产生的模型将预测控制冰流速度和几何演变的温带冰、水、应力、变形和基底滑移的耦合分布。建模将导致参数化，使冰流能够以一种简化但物理上可防御的方式包括在大陆尺度的冰盖模型中。

Iverson/1643120This award supports a project to study temperate ice, using both experimental methods and modeling, in order to determine the effect of water on its flow resistance and structure and to study the mobility of water within the ice. A new mathematical model of ice stream flow and temperature is developed in conjunction with these experiments. The model includes water production, storage, and movement in deforming ice and their effects on flow resistance at ice stream margins and on water availability for lubrication of ice stream beds. Results will improve estimates of the evolution of ice stream speed and geometry in a warming climate, and so improve the accuracy of assessments of the contribution of the Antarctic ice sheet to sea level rise over the next century. Ice streams are zones of rapid flow within the Antarctic ice sheet and are primarily responsible for its discharge of ice to the ocean and major effect on sea-level rise. Water plays a central role in the flow of ice streams. It lubricates their bases and softens their margins, where flow speeds abruptly transition from rapid to slow. Within ice stream margins some ice is "temperate", meaning that it is at its melting temperature and thus contains intercrystalline water that significantly softens the ice. Two postdoctoral researchers will be supported, trained, and mentored for academic careers, and three undergraduates will be introduced to research in the geosciences.This award is part the NSF/GEO-UK NERC lead agency opportunity (NSF 14-118) and is a collaboration between Iowa State University in the United States and Oxford University in the United Kingdom. The two-phase deformation of temperate ice will be studied, with the objective of determining its effect on the flow of Antarctic ice streams. The project has two components that reinforce each other. First there will be laboratory experiments in which a rotary device at Iowa State University will be used to determine relationships between the water content of temperate ice and its rheology and permeability. The second component will involve the development at Oxford University of a two-phase, fluid-dynamical theory of temperate ice and application of this theory in models of ice-stream dynamics. Results of the experiments will guide the constitutive rules and parameter ranges considered in the theory, and application of elements of the theory will improve interpretations of the experimental results. The theory and resultant models will predict the coupled distributions of temperate ice, water, stress, deformation, and basal slip that control the evolution of ice-stream speed and geometry. The modeling will result in parameterizations that allow ice streaming to be included in continental-scale models of ice sheets in a simplified but physically defensible way.