Seismological Investigation of Columbia Glacier Calving Mechanics

冰山崩解是许多海洋冰川质量损失的主要组成部分，与冰川退缩的动力学密切相关。尽管它的重要性，产犊过程是非常了解。 需要了解产犊和冰川动力学变得更加紧迫的阿拉斯加冰川在现代全球物质平衡的重要性是更好地理解，现代冰川的效用作为类似物的快速撤退的海洋为基础的古冰盖的认可。自20世纪80年代初以来，人们一直在研究哥伦比亚冰川，并获得了大量非常有用的数据。然而，随着哥伦比亚冰川退缩速度的加快，研究它的重要性也在增加。 它是阿拉斯加最后一个从延伸位置退缩的主要冰川，也是目前世界上最快的冰川。（以12公里/年计算），每年约有22立方公里的冰通过裂冰作用排入海洋，并可能在25年或更短的时间内完全消退。首席研究员将追求三个目标：1）详细分析1997- 1999年的摄影资料所确定的运动学，该摄影资料描述了冰川末端约4公里范围内的流动状况、应变率特征、边界牵引力和河床深度。将根据1999年地面摄影的地面摄影测量完成对冰川最低5公里处应变率空间不均匀性的地质统计分析。2000年和2001年还将进行更多的空中摄影，以补充这项工作。 上游传播的运动波的理论分析与不可逆的潮汐后退，这表明如何基底滑动可能是最终的原因，情节和一般不可逆的性格的潮汐后退将被解决; 2）观测冰川冰震和崩解活动，使用现代地震记录设备是相对不成熟的。主要研究者将分析这些数据集，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性。他还将对烟纸记录进行数字化处理，以便在标准软件包中进行分析，并将改进的事件探测软件应用于数字化数据集; 3）2002年8月的照片飞行是1976年开始的一系列航空摄影中的第124和125次飞行，我们对1980年左右以来撤退模式的大部分知识都是基于这些飞行。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不是。因此，问题的最困难的部分是适合冰川学家的技能比摄影测量师，所以他将购买新的数字（“软拷贝”）摄影测量软件。

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.