Seasonal variations in proglacial lake area revealed by high spatial resolution planetscope satellite imagery

Abstract Seasonal variations in proglacial lakes are often omitted from long‐term records of lake behaviour due to the trade‐off between high‐spatial versus high‐temporal resolution satellite imagery. Understanding the impact of these short‐term fluctuations on long‐term studies of proglacial lake growth is essential for accurately predicting future growth, as well as for understanding the risk of jökulhlaups or glacial lake outburst floods (GLOFs). Here, we use high spatial resolution (3.7 m) PlanetScope imagery to detect short‐term variations in the area of Fjallsárlón, a large proglacial lake in southeast Iceland. We demonstrate that between 2017 and 2023, moderate resolution imagery underestimates seasonal variations in lake behaviour by ~7% compared with PlanetScope imagery. In addition, the use of a single image from summer months (June to August) underestimates the annual maximum lake area by up to ~2%. The omission of these short‐term variations in longer‐term studies risks misrepresenting patterns of lake growth and behaviour, which has implications for glacier retreat, contribution to sea level rise and downstream flood risk from GLOFs.