Meteorological drivers of seasonal motion at the Barry Arm Landslide, Prince William Sound, Alaska

Global climate change creates geologic hazard cascades as the cryosphere experiences warming. The rapid retreat of Barry Glacier, a tidewater glacier in Prince William Sound, Alaska, has destabilized the cliff walls adjacent to the fjord, including a large landslide, approximately 2-km-wide, 1-km-tall, and ∼500 Mm3 in volume. The Barry Arm landslide was first identified in 2019 but has since been noted in photographs dating back to the 1930s. Catastrophic failure of the landslide has the potential to generate a tsunami with life-threatening waves in nearby fjords, including the port town of Whittier, 60 km from the landslide. Since monitoring began in 2021, slow downslope movement with short periods of acceleration has been observed. In this study, we refine the observations of landslide acceleration and correlate these periods with meteorological observations to assess the potential for further acceleration and catastrophic failure. We use ground-based synthetic aperture radar data (GBInSAR) collected sub-hourly from a location across the Barry Arm fjord since May 2022 with a line of sight that captures ~90% of the downslope landslide vector movement to generate time series of the landslide’s three main kinematic elements (distinct regions of deformation). This time series shows landslide-wide motion from late August to early November 2022 (2 months) at rates of 20-80 mm/day, then again from late September to mid-October 2023 (1.5 months) at 10-20 mm/day. No landslide-wide motion was detected in 2024. The Cascade Glacier sits stratigraphically above and to the northwest of the landslide and has been identified as a potential source of water for the landslide system. Ice-penetrating radar data collected in 2024 show an over-deepened section of Cascade Glacier adjacent to the most active kinematic element of the landslide, the Kite, suggesting melt water might pool and subsequently seep into the Kite kinematic element. Two full meteorological stations, each with additional node stations, monitor weather near the landslide and provide 15-minute precipitation and temperature data. We combine a simple positive degree-day factor melt model with precipitation analysis to show that the timing of movement of the Kite is correlated with the effects of seepage into the landslide subsurface, which are primarily driven by snow and ice melt. Understanding links between landslide displacement and melting of snow and ice could potentially lead to the use of meteorological conditions or forecasts as an additional risk assessment tool for identifying when the hazard of failure could be most severe. Our study accompanies others’ analyses of the Barry Arm Landslide using lidar, satellite InSAR, seismic, and infrasound data and contributes to our limited but critical understanding of landslide hazards in Alaska.