Assessing Glacier Dynamics and Debris-Cover-Controlled Ablation in Svalbard: Insights from Gåsbreen (2003 2023)

Abstract

The Svalbard Archipelago is a highly glaciated region, making it particularly sensitive to progressive climate shifts. This sensitivity is evident in the major changes observed in glacier dynamics. For this reason, both experimental observations and long-term monitoring of glaciers' mass loss in Svalbard are necessary and urgent. Responding to these needs, this study presents a quantitative analysis of melt rate and mass balance of Gåsbreen – a debris-covered land-based glacier located in Hornsund fjord, Spitsbergen. We combined a direct observation on the glacier with satellite data spanning the period 2003–2023 to quantify glacier dynamics and the role of debris cover on glacier ablation. Results covering the study period (2003–2023) indicate a shrinking glacier area (1.47 ±0.07 km 2 ) and a notable retreat of the lower terminus (280 ± 45 m at a rate of 13.3 ma melting doubled in recent years (2016–2023: 0.78 ± 0.07 km 2 a 1 1 ). Notably the rate of ). The surface elevation changes across the glacier ranged within ±2 m a 1 , indicating moderate spatial variability between the ablation and accumulation zones. The computed total ice flux was ~9.9 × 10 5 m yr 1 m 3 yr 1 , corresponding to a mean emergence velocity of 0.09 . Overall, Gåsbreen exhibited a slight positive average mass balance of 0.13 m w.e. a 1 , suggesting that accumulation marginally exceeded ablation during the study period. Approximately 10% of the glacier area was covered by debris during the study period, with a noticeable increase in debris accumulation observed during 2016–2023. Importantly, analysis of ablation rates revealed varying thinning rates across different debris thickness categories, with a significant reduction (25–30%) in ablation rates observed over thicker debris. The study also highlights the projected increase in debris cover and its implications for glacier morphology including the formation of supraglacial ponds and ice cliffs, which are anticipated to contribute significantly to total mass loss. This quantitative assessment provides new insights into the complex interplay between debris thickness and glacier response to the warming climate.