Assessing movement of the Barry Arm landslide using multi-sensor repeat topographic and bathymetric surveys

Abstract:

Ongoing global atmospheric warming is pushing the mean annual air temperature above freezing in many high elevation and high latitude areas. This change in climate is having a dramatic influence on the cryosphere, including the continued mass loss of glaciers, and the widespread warming and thawing of permafrost. As permafrost thaws and glaciers thin and retreat, support of valley walls is greatly diminished or removed, leading to slope failures; landslides entering a lake or a fiord have the potential to generate tsunamis.

A large landslide in Barry Arm, a fiord in northwest Prince William Sound, 100 km east of Anchorage, Alaska, has the potential to slide into the water and generate a tsunami that could have devastating local effects on fishermen and recreationists using the area, and potentially impact nearby communities and infrastructure. Barry Glacier, like many tidewater glaciers in Alaska, has thinned and retreated rapidly in the last two decades, exposing valley walls that were previously buttressed by the glacier. Previous studies that analyzed optical satellite imagery indicated that landslide movement covaried with the retreating terminus of Barry Glacier, with rapid changes in both occurring between 2009 and 2015, and a reduced rate of movement in recent years. Here we present results from repeat airborne lidar surveys, and autonomous surface vehicle and ship-based bathymetric surveys of this recently deglacierized, unstable mountain slope near the terminus of Barry Glacier. These new, high-resolution datasets, acquired during summer and fall of 2020, reveal continued, differential movement of the slope, though at a much slower speed than previously measured. The multi-sensor-derived topography-bathymetry product shows both subaerial and submarine components of the landslide and allows the complete landslide morphology to be assessed. Future paired topographic and bathymetric surveys will allow us to monitor changes in the full landslide as Barry Glacier continues to retreat, removing support from the base of the unstable slope.