Icebergs Modify Antarctic Landfast Sea Ice Mass Balance

Abstract. Icebergs locked in landfast sea ice strongly modify snow redistribution on Antarctic landfast sea ice, with important but still poorly constrained consequences for local ice and snow mass balance and ecology. Here, we revisit ice and snow accumulation around icebergs in Atka Bay (eastern Weddell Sea) using a combination of a digital elevation model (DEM) generated from drone photogrammetry, ground-based electromagnetic (EM) induction sounding, manual drilling, snow pits, and ice core analyses. The DEM reveals a characteristic snowdrift morphology consisting of a thick windward drift, two lateral drifts, and a snow-free tail, consistent with previous airborne observations. Snow depths derived from the DEM agree well with manual measurements. Snow properties in the drifts are dominated by dense, wind-compacted slabs. Despite substantial snow loading in drift areas, only limited slush was observed at the snow–sea ice interface, with maximum slush thicknesses of 20 cm. Instead, heavily snow-loaded areas coincide with anomalously thick sea ice (7.8 m), compared to 1.6 m in areas with undisturbed snow cover. Ice core analyses indicate extensive snow-ice formation, suggesting efficient refreezing of flooded snow and a substantial contribution to sea ice mass balance. Basal-origin ice is inferred to be thinner beneath the drifts, while thicker consolidated ice was observed in the snow-free tail. In contrast to previous airborne and modeling studies that limited mass-balance assessments to the snow distribution, this study provides direct, co-located observations of snow, slush, and ice properties, providing evidence that iceberg-induced snowdrifts in Atka Bay can promote substantial snow-ice formation and upward ice growth.