Sub-monthly to inter-annual Arctic gravel beach change and controlling factors

Sixteen uncrewed aerial vehicle (UAV) surveys were conducted along a 2.5 km stretch of coastline of Isbjørnhamna, Hornsund, Svalbard during summer months between 2018 and 2025 to quantify topographic change within a gravel beach neighboring the Polish Polar Station (PPS) from days to years. Spectral wave model of Herman et al. (2025) was used to extract hourly nearshore significant wave height, peak period, energy period and wave energy flux. The model was validated against observational data of Swirad et al. (2023). Storms were extracted as events when significant wave height exceeded 95th percentile. Near-daily high-resolution ice/open water maps of Swirad et al. (2024) were used to create timeseries of ice coverage in the main basin of Hornsund and in Isbjørnhamna. Hourly wave runup was calculated for 10 m alongshore blocks using wave parameters, beach topography and an empirical runup formula developed by Poate et al. (2016) for gravel beaches. Wave runup combined with water level was used to extract timing of wave overtopping and coastal flooding.We observed a great inter-annual variability in wave and ice conditions with the icy 2019/20 and 2021/22, the stormy 2018/19, 2020/21 and 2022/23, and the moderate 2023/24 and 2024/25. There was a great variability in volumetric coastal change with near-zero change after 7 years. Erosion focused in some hotspots, notably the vicinity of the PPS infrastructure, while the eastern part of the analysed beach experienced net deposition. At the sub-monthly to monthly scales high rates of coastal change were related to beach erosion by moving growlers, development of beach cusps, melting of ice buried under beach sediments and hydrological processes. References:Herman A., Swirad Z.M. & Moskalik M. 2025. Increased exposure of the shores of Hornsund (Svalbard) to wave action due to a rapid shift in sea ice conditions. Elementa: Science of the Anthropocene 13(1): 00067. https://doi.org/10.1525/elementa.2024.00067Poate T.G., McCall R.T. & Masselink G. 2016. A new parameterisation for runup on gravel beaches. Coastal Engineering 117: 176–190. https://doi.org/10.1016/j.coastaleng.2016.08.003Swirad Z.M., Moskalik M. & Herman, A. 2023. Wind wave and water level dataset for Hornsund, Svalbard (2013–2021). Earth System Science Data: 15, 2623-2633. https://doi.org/10.5194/essd-15-2623-2023Swirad Z.M., Johansson A.M. & Malnes E. 2024. Extent, duration and timing of the sea ice cover in Hornsund, Svalbard, from 2014–2023. The Cryosphere 18: 895-910. https://doi.org/10.5194/tc-18-895-2024