Distribution and characteristics of supraglacial channels on mountain glaciers in Valais, Switzerland

Abstract

Supraglacial channels form a key component of glacier hydrology, transporting surface meltwater to englacial and proglacial positions, which impacts ice flow dynamics, surface mass balance and the hydrochemistry of glacial runoff. The presence of supraglacial channels is well-documented on ice sheets using satellite imagery, but much less is known about their properties on mountain glaciers. Here we use high-resolution (0.1 m) orthophotos to identify channels across 285 glaciers in Valais Canton, Switzerland. For the 85 glaciers with visible supraglacial drainage networks, we map 1890 channels (>0.5 m wide) and investigate their distribution and characteristics. We find that mean elevation and slope exert the strongest influence on glacier drainage density, with glaciers characterised by shallow slopes (which have fewer crevasses) and a large portion of their area at lower elevations (resulting in a higher meltwater supply) exhibiting higher drainage densities. There is also significant inter-glacier variability in channel termini locations. On average, 80 % of channels drain across the glacier surface and directly onto proglacial areas, with only 20 % terminating englacially. However, 48 % of glaciers contain no englacially-terminating channels and 3.5 % of glaciers host channels that all terminate englacially. Lastly, most channels on glaciers in Valais are only slightly sinuous, with higher sinuosities typically occurring in flatter areas and associated with patchy debris cover. Future research should assess the importance of channels below our mapping resolution and investigate how drainage networks may evolve under continued climatic warming.