Seismological Investigation of Columbia Glacier Calving Mechanics

哥伦比亚冰川崩解机制的地震学研究

• 批准号: 0240972
• 负责人: W. Tad Pfeffer
• 金额: $ 9.19万
• 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: 2003
• 资助国家: 美国
• 起止时间: 2003-05-15 至 2005-04-30
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0240972&HistoricalAwards=false
• 关键词: Seismological; Investigation; Columbia; Glacier; Calving

ABSTRACTOPP-024072PfefferIceberg calving is a major component of mass loss from many marine glaciers and is intimately connected with the dynamics of tidewater glacier retreat. Despite its importance, the calving process is very poorly understood. The need to understand calving and tidewater glacier dynamics becomes more pressing as the importance of Alaskan glaciers in modern global mass balance is better understood, and as the utility of modern tidewater glaciers as analogs for rapid retreat of marine-based paleo ice sheets is recognized. The Columbia Glacier has been studied since the early 1980's, and has yielded a large volume of very useful data. The importance of studying Columbia Glacier increases, however, as its retreat accelerates. It is the last of Alaska's major tidewater glaciers to retreat from its extended position, and currently the world's fastest glacier (at 12 km yr-1), which discharges approximately 22 km3 per year of ice into the ocean via calving, and may complete its retreat within 25 years or less.The Principal Investigator will pursue three objectives: 1) a detailed analysis of kinematics determined from the 1997- 1999 photography which describes the flow regime, strain rate characteristics, boundary tractions, and bed depth in the glacier channel within about four km of the terminus will be done. Geostatistical analysis of spatial heterogeneity of strain rates in the lowest five km of the glacier, based on terrestrial photogrammetry from 1999 ground-based photography will be completed. This work will be supplemented by additional aerial photography from 2000 and 2001. Theoretical analysis of upstream propagation of kinematic waves associated with irreversible tidewater retreat which shows how basal sliding may be the ultimate cause of the episodic and generally irreversible character of tidewater retreat will be addressed; 2) Observations of glacial icequake and calving activity using modern seismic recording equipment is relatively immature. The Principal Investigator will analyze these data sets to develop techniques that will improve future deployment and data analysis. The goal is to determine first-order time and frequency domain source characteristics, using known seismic sources. He will also digitize the smoked-paper records to enable analysis in standard software packages and apply the refined event detection software to the digitized data set; and 3) The August 2002 photo flights are the 124th and 125th flights in an unbroken series of aerial photography started in 1976, and from which most of our knowledge on the pattern of retreat since around 1980 is based. Future photogrammetric analysis now becomes his responsibility because the photogrammetric procedures are fairly straightforward, but the actual process of recognizing the correct features in the photography is not. Thus, the most difficult part of the problem is suited to the skills of a glaciologist than a photogrammetrist, so he will purchase new digital ('softcopy') photogrammetric software.

ABSTRACTOPP-024072Pfeffer 冰山崩解是许多海洋冰川质量损失的主要组成部分，与潮水冰川退缩的动态密切相关。尽管产犊过程很重要，但人们对它却知之甚少。 随着人们更好地理解阿拉斯加冰川在现代全球质量平衡中的重要性，并且认识到现代潮水冰川作为海洋古冰盖快速退缩的类似物的效用，了解崩解和潮水冰川动力学的必要性变得更加紧迫。自 20 世纪 80 年代初以来，人们一直在研究哥伦比亚冰川，并产生了大量非常有用的数据。然而，随着哥伦比亚冰川退缩的加速，研究哥伦比亚冰川的重要性也随之增加。 它是阿拉斯加最后一个从伸展位置退缩的主要潮水冰川，也是目前世界上速度最快的冰川（每年 12 公里），每年通过崩解向海洋排放约 22 平方公里的冰，并可能在 25 年或更短的时间内完成退缩。首席研究员将追求三个目标：1）对 1997-1999 年摄影确定的运动学进行详细分析，描述流程 将完成终点站约四公里范围内冰川通道的状态、应变率特征、边界牵引力和河床深度。基于 1999 年地面摄影测量的地面摄影测量，将完成冰川最低 5 公里处应变率空间异质性的地统计分析。这项工作将得到 2000 年和 2001 年额外航空摄影的补充。将讨论与不可逆潮水退缩相关的运动波上游传播的理论分析，这表明基底滑动可能是潮水退缩的间歇性和一般不可逆特征的最终原因； 2）利用现代地震记录设备对冰川冰震和冰崩活动的观测还比较不成熟。首席研究员将分析这些数据集，以开发改进未来部署和数据分析的技术。 目标是使用已知的地震源确定一阶时域和频域源特征。他还将把烟纸记录数字化，以便在标准软件包中进行分析，并将精细的事件检测软件应用于数字化数据集； 3) 2002 年 8 月的摄影飞行是 1976 年开始的不间断航空摄影系列中的第 124 次和第 125 次飞行，我们对 1980 年左右撤退模式的大部分了解都是基于这些飞行。未来的摄影测量分析现在成为他的责任，因为摄影测量程序相当简单，但识别摄影中正确特征的实际过程却并非如此。因此，问题中最困难的部分是适合冰川学家而不是摄影测量师的技能，因此他将购买新的数字（“软拷贝”）摄影测量软件。