Measurement of Short Period Motion On A Fast Moving Glacier and Analysis of Data (Abstract)

Abstract

The investigation of glacier motion over short time periods for relatively long duration and over large longitudinal extent can yield valuable insight into the dynamics of glacier surging, basal sliding, ice stream development, and calving mechanisms. In this paper, we discuss techniques for monitoring short term horizontal and vertical motion employed on the often highly-fractured surface of Variegated Glacier, Alaska, prior to its recent surge (1980—84) and on the fast-moving outlet glacier — ice stream system of Jakobshavns Glacier, Greenland. The short period measurements described here were made continuously over one to several months, and, in many cases, encompass seasonal and longer term fluctuations as well. The positions of a relatively large number of surface markers (15-35) were followed as functions of time. Application of standard terrestrial surveying techniques and modern microwave and UHF positioning methods to these short period studies are discussed. We then describe methods of reduction and analysis on the resulting large data sets, which may be treated as quasi-stationary time series. Examples of correlation with other glacier variables, such as basal water pressure, seismicity, and stream discharge are given and the propagation of movement events discussed.