A Decade of Monthly Frontal Ablation at 147 Tidewater Glaciers in Svalbard

Abstract. We present a novel, regional-scale monthly analysis of frontal ablation at 147 tidewater glacier basins in Svalbard from January 2015 through December 2024. A multi-temporal, deep-learning segmentation model was implemented to reduce the manual labor cost inherent to mapping 203,294 terminus positions, yielding 15,647 monthly-averaged calving fronts derived from Sentinel-1 SAR imagery. In addition, a monthly ice discharge time series is developed from the extensive ITS_LIVE velocity database, as well as regionally existing ice thickness products. To account for ice mass loss due to surface processes between the fluxgate and terminus (i.e. the glacier domain), the climatic mass balance is integrated over the domain area using monthly aggregated daily outputs from the MAR regional climate model. The result is a frontal ablation time series at an unprecedented spatio-temporal scale with 15,500 monthly estimates of frontal ablation, allowing new insights and progress towards a process understanding of frontal ablation. The mean annual frontal ablation rate across all glaciers from 2015 to 2024 is 21.57 ± 0.97 Gt a^-1. The Austfonna ice cap accounts for ~48% of Svalbard's frontal ablation, due to the dominant Austfonna Basin 3, with a 5.05 ± 0.35 Gt a^-1 annually averaged rate. As frontal ablation measurements have historically been limited to annual and decadal temporal resolution, this dataset addresses the intra-annual and seasonal variability knowledge gap, while providing valuable reference data for the modeling community. The frontal ablation, ice discharge, and calving front time series are publicly available at https://doi.org/10.5281/zenodo.19481461 (Pyles et al., 2026).