Characterizing submarine ice roughness at icebergs from a temperate tidewater glacier

Abstract Glacier ice melt, a key driver of sea level rise, depends on how the ocean currents interact with ice. The roughness and shape of the ice on scales smaller than 10 m are important and remain poorly understood due to a lack of observations. We investigate submarine ice roughness using fine-resolution multibeam sonar measurements from 13 grounded icebergs and a drone survey of a recently capsized floating iceberg in the temperate tidewater glacial fjord Xeitl Geeyi’ (LeConte Bay), Alaska. From these 14 icebergs, 55 gridded iceberg surfaces (20–40 cm resolution) were derived. We apply a spectral, scale-resolved approach to quantify iceberg roughness. Spectral analysis shows that 40 of these surfaces were dominated by vertically oriented channels with wavelengths ranging from 0.9 m to 3.7 m, likely shaped by buoyancy-driven meltwater plumes. Statistical analyses reveal a mean peak wavelength of 1.9 m, RMS height of 0.3 m, skewness of -0.3 and kurtosis of 4.3. Roughness at medium- to small-scales $\mathcal{O}$ (0.5-5 m) can nearly double the ice–ocean boundary surface area and, when combined with iceberg-scale morphology $\mathcal{O}$ (10 m), underscores the need to integrate realistic roughness and morphology parameters into melt models, which may improve melt predictions.