Coastal Freeze

The rapid decline in landfast ice in the coastal Arctic is increasing the duration of wave exposure and strength of wave energy reaching the coast each year. Because landfast ice forms in shallow water, entrainment in ice also plays a key role in mediating sediment export (where it can exceed the annual regional river input). The overarching aim of the proposed work is to understand the feedbacks between new landfast ice formation, surface waves, and sediment transport during the highly spatially and temporally heterogeneous freeze-up period each autumn. The field experiment will use moorings, autonomous systems, and seafloor cables to capture the spatio-temporal variability in freeze-up processes over an approximately 75 km x 50 km region on the Alaskan Beaufort shelf. Our research will take a nested approach, utilizing seasonal observations and pre-existing inter-annual time series to capture the roles of offshore forcing, local hydrodynamic processes, and air-sea exchange. Measurements will be made using novel integration of multiple new low-cost telemetered sensors, amphibious drones, seafloor cables, and traditional moorings optimized for harsh Arctic conditions.

We hypothesize that surface waves modulate ice formation both through thermodynamics, by enhancing sensible heat loss, and through momentum transfer, where radiation stress gradients drive transport. We expect that sediment resuspension and availability will follow related spatial and temporal gradients during the freeze-up season, where the relative timing of storms and freezing onset in a given year plays a significant role in the rate of ice formation, ice sediment entrainment, and relative shutdown of sediment transport for winter. The expected outcomes of this project include better predictions of the atmospheric and off-shelf conditions that lead to landfast ice formation, and improved understanding of the sediment pathways during the autumn freeze-up season.