Structural weaknesses in ice mélange revealed by high resolution ICEYE SAR imagery

The mixture of icebergs and sea ice in tidewater glacier fjords, known as ice mélange, is postulated to impact iceberg calving directly through physical buttressing and indirectly through freshwater fluxes altering fjord circulation. In this contribution, we assess the textural characteristics of ice mélange in summer and winter at the terminus of Helheim Glacier in Greenland using high resolution (1-3 m) X-band Synthetic Aperture Radar (SAR) imagery from the ICEYE small satellite constellation. The Grey Level Co-occurrence Matrix (GLCM) and statistical variations in pixel intensity downfjord reveal structural banding within the mélange matrix in both summer and winter. The boundary between these bands represent shear zones, demonstrating structural weaknesses in the mélange that may persist throughout the year. Furthermore, we compare two iceberg segmentation methods, texture-based vs the Segment Anything Model (SAM). Both techniques detect large (>0.1 km2) icebergs in summer when pixel variations are larger, but SAM has high iceberg detection accuracy in both seasons. The detected icebergs stabilise near the mélange shear zones, suggesting they act as the nucleus of the mélange bands and control matrix stability. Our study demonstrates the potential for using high resolution ICEYE SAR imagery for studying dynamic processes in glaciology and beyond.