Untitled

Abstract

Glacial ogives are transverse topographic, wave-like surface features that form below icefalls on some alpine glaciers. Groundpenetrating radar surveys from the Gorner glacier system in the Swiss Alps reveal an along-fl ow periodicity in scattering intensity that correlates with ogives. The scattering appears in the ablation zone and occurs at 5-20 m depth. The geometry of the scattering mimics that of the ogives, although exaggerated in amplitude. We interpret the scattering to represent lateral variations in water content. We propose that as glacial ice accelerated and stretched through the icefall, seasonal fl uctuations occurred in water infi ltration to crevasses during the summer and subsequent freezing of that water in the crevasses in the winter. This seasonally varying infi lling and freezing locally altered the distribution of temperature, creating zones of temperate ice with water inclusions that preferentially scatter radar energy. In addition to the scattering pattern, highly refl ective planar features associated with these periodic regions of temperate ice are interpreted as water-fi lled fractures. A three-dimensional rendering of the orientation of these planar features precludes a "fold-and-thrust" hypothesis for the formation of the ogives.

Joint geodetic and seismic analysis of surface crevassing near a seasonal glacier-dammed lake at Gornergletscher, Switzerland

“…This glacier has an area of 60 km 2 , stretches 14 km in length over altitudes 2200–4550 m with a maximum ice thickness of more than 400 m (Huss, 2005). The Gornergletscher system has been the subject of research for several decades (Bezinge and others, 1973; Aschwanden and Leibundgut, 1982; Haeberli and Funk, 1991; Iken and others, 1996; Lüthi and Funk, 2000, 2001; Suter and others, 2001; Walter and others, 2008; McBride and others, 2012). Within the glacier system, we focus on a region located at the confluence of two large tributary glaciers, Gornergletscher and Grenzgletscher, at an elevation of 2600 m ~5 km from the glacier terminus.…”