Investigating the signature of a tidewater glacier surge behaviour using geomorphological, sedimentological and geotechnical data: Borebreen, Svalbard.

The sedimentary processes taking place beneath contemporary surging glaciers are difficult to observe directly, yet they are crucial for building a holistic understanding of glacier surge processes and mechanisms. Settings where the sediment-landform assemblages characterising the ice-bed interface are preserved without significant modification are therefore an important archive of the subglacial processes that are active during a surge. At tidewater surging glaciers, landforms are often excellently preserved in a submarine setting, but analysis of these beyond mapping from high-resolution bathymetry data (where available) can be limited. However, in most cases, there are also subaerially exposed sediments and landforms at the terrestrial fjord margins, providing an accessible and rich source of data of the subglacial environment of a surging glacier. Borebreen is a tidewater glacier on the northwestern side of Isfjorden in Svalbard. Previously published detailed bathymetric data has identified a suit of submarine glacial landforms formed during the last surge of Borebreen ~100 years ago. The subsequent quiescent phase has exposed a wide spread of crevasse-squeeze ridges (CSRs) both in the fjord and on the terrestrial margins. These are important landforms that are unique to surging glaciers and can therefore provide information concerning surge dynamics and subglacial processes. We present initial geomorphological and geotechnical data from the CSRs through mapping and direct measurements using a hand-held shear vane test, pocket penetrometer and particle size analysis. High-resolution orthmosaics and Digital Elevation Models (DEMs) from drone surveys of the proglacial foreland were collected in order to assess the spatial pattern of CSRs and a Python-based ArcGIS toolbox was used to automatically extract 3D morphometric data from the DEMs. These data provide an opportunity to investigate the links between the sediment geotechnical properties, CSR geometries and surge processes and mechanisms; such as the identification of spatial patterns in the state of sediment consolidation within CSRs and CSR morphometrics.