Longyearbyen Lagoon (Spitsbergen): Gravel Spits Movement Rate and Mechanisms

Understanding lagoon behavior is crucial for both scientific research and engineering, especially in delicate Arctic environments. Lagoons are vital to coastal areas, often bol-stering infrastructure resilience. Since Spring 2019, we've monitored the Longyearbyen lagoon (Spitsbergen), vital for coastal erosion defense and serving as a natural laboratory. The location's well-developed infrastructure and accessible logistics make it an ideal testing site available at any time. It can be used for many natural scientific studies. Spanning 400x50m, the lagoon continually shifts due to waves and tides, with a maximum tidal range of 2m. This article focuses on gravel spit movement, accelerating in recent years to several meters monthly. Through methods like aerial and satellite images, laser scanning and hydrodynamic measurements, we've delineated processes, rates, and mechanisms behind this movement. Bed-load transport along the spit, coupled with gravel slides, primarily drives expansion and lagoon growth. Modeling these processes aids in forecasting lagoon system development, crucial for informed management and engineering decisions in Arctic coastal regions.