Classifying Glacier-Bed Interactions at Nigardsbreen, Norway Using Striae and Directional Landforms

Session: 37th Annual Undergraduate Research Exhibition Sponsored by Sigma Gamma Epsilon (Posters)

Presenting Author:

Authors:

Abstract:

This study investigates the glacial abrasion patterns at Nigardsbreen, a temperate outlet glacier of the Jostedalsbreen Ice Cap, Southern Norway. This accessible site is ideal for striation analyses due to recent exposure from continuous retreat. Current glacier flowline models often assume spatially uniform basal conditions, oversimplifying how ice interacts with variable terrain and generating inaccurate predictions. This research provides a spatial classification of glacier-bed interaction at Nigardsbreen, revealing that directional and geometric variability in striation clusters reflects distinct zones of basal shear, erosion and stable sliding. These divisions provide a field-based framework to constrain subglacial processes in flowline models. Field data were collected using a geologic compass, measuring tape, and digital calipers, then analyzed using circular statistics, Python, ArcGIS, and Google Earth Pro. We recorded over 430 striations (µ: 147.5°, 𝜎: 7.7°), 22 chattermarks (µ: 133°, 𝜎: 15.1), and 24 meso-scale bedrock lineaments found in mafic intruded granitic orthogneiss (µ: 139.9°, 𝜎: 61.2°). Rose diagrams (created in Python using NumPy and Matplotlib) were used to visualise directional patterns, and the Mardia-Watson-Wheeler test for homogeneity was applied to assess whether striations, chattermarks and meso-scale bedrock features were statistically distinct. The results showed significant differences between groups (p < .0001) which confirmed their independence despite superficial similarities. Azimuth-width-length trend plots were used to classify striation clusters into zones of moderate basal shear, erosion and stable sliding. Mapped in ArcGIS, these categories produced a spatial interpretation of glacier-bed interaction across the retreat path of Nigardsbreen. Interpretations suggest that striation azimuths represent primary ice flow direction, to the southeast parallel to the km-scale valley, while chattermarks may record episodic shifts in flow direction and basal shear. The lack of alignment between both striations and chattermarks with the meso-scale bedrock features (30-80m in length) confirmed that ice movement was not constrained at the decameter-scale. This method captured not only the directional trends but also morphometric characteristics of ice-bed interaction, revealing zones where basal conditions transition from sliding to stress accumulation and local erosion. Directional analysis of striations is a low-cost, high-resolution tool that supports the classification of distinct glacier-bed regimes and demonstrates how directional morphometrics can be used to identify zones of sliding, stress accumulation or erosion. This provides field-based constraints for spatially variable basal drag in flowline models.