Characterization of subglacial marginal channels using 3-D analysis of high-density ground-penetrating radar data

Abstract

Studying subglacial drainage networks is important for understanding the potential relationship between channel dynamics and rapid glacier recession as well as the role of subglacial channels in subglacial sediment evacuation. In order to delineate the planform geometry of snout marginal subglacial channels, densely spaced ground-penetrating radar (GPR) measurements at a frequency of ~70 MHz were carried out over the snout marginal zones of two temperate glaciers in the southwestern Swiss Alps, the Haut Glacier d'Arolla and the Glacier d'Otemma. Three-dimensional (3-D) data processing and amplitude analysis of the GPR reflection along the glacier bed was used to map the channels. At the Haut Glacier d'Arolla, two relatively straight channels of several meters in width were identified. The positions of these channels correspond well with the locations of channel outlets at the glacier terminus, as well as with fractures appearing on the glacier surface one month after the GPR data acquisition. The latter are believed to represent the beginning of ice collapse above the subglacial channels. At the Glacier d'Otemma, a major subglacial conduit was detected with similar dimensions to those identified at the Haut Glacier d'Arolla, but greater sinuosity. The position of this channel was confirmed by drone-based imagery acquired after glacier margin collapse. Our results confirm that high-density 3-D GPR surveys can be used to map subglacial channels near temperate alpine glacier margins.

Ground-penetrating radar imaging reveals glacier's drainage network in 3D

“…Alongside Harper et al (2010) and Egli et al (2021), this study is one of a few times that a glacier's drainage network is imaged in 3D with GPR data, thus providing highresolution information of the geometry from such a system. The Rhonegletscher's drainage network identified in this study has a meandering nature throughout the survey area, with an increasing network width towards the terminus of the glacier.…”

“…A 3D GPR data set was used by Harper et al (2010) to investigate basal crevasses and the subglacial hydraulic network on Bench Glacier, Alaska. More recently, Egli et al (2021) acquired and processed 3D GPR surveys over two Swiss glaciers and successfully imaged the subglacial drainage network with the analysis of the reflected GPR amplitudes. Several glaciological studies (Schaap et al, 2019;Hansen et al, 2020;Church et al, 2020) have used multiple 2D GPR profiles to investigate the englacial drainage structure in both cold and temperate ice; however, as far as we are aware, there are no studies leveraging 3D GPR in order to image an englacial drainage network.…”

UAV and GPR Data Integration in Glacier Geometry Reconstruction: A Case Study from Irenebreen, Svalbard

“…GPR has been proven to be an effective tool for glacier thickness and inner structure mapping [39][40][41][42]. Approximately 21 km of GPR profile lines were recorded on Irenebreen (Figure 2).…”

“…198-246), as well as in samples of glacier ice [75,76]; also, this value is obtained in most cases of direct measurements in the field, where glaciers consist of cold ice [24] (pp. [32][33][34][35][36][37][38][39][40][41][42][43][44][45][46][47][48].…”

Subsurface Flow Path Modeling From Inertial Measurement Unit Sensor Data Using Infinite Hidden Markov Models

“…In karst studies, direct measurements of underground rivers would add to the knowledge needed for ground water monitoring and management [2]. Often, the subsurface mapping is done using ground penetrating radars (GPR) [3]- [5]. However, the material composition can effect the range of GPR and image quality, and high energy consumption can limit extensive field surveys.…”