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Open Water Sediment Dynamics on the Alaskan Beaufort Sea Shelf: A Numerical Modeling Study
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  • Brianna Undzis,
  • Julia M. Moriarty,
  • Emily Eidam,
  • Irina Overeem
Brianna Undzis
University of Colorado Boulder

Corresponding Author:brianna.undzis@colorado.edu

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Julia M. Moriarty
University of Colorado - Boulder
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Emily Eidam
Oregon State University
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Irina Overeem
University of Colorado Boulder
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Abstract

Sediment dynamics on continental shelves can impact coastal geomorphology, habitat suitability, and biogeochemical cycling. In the coastal Arctic, for example, the rate at which sediment is transported to locations where it can be sequestered impacts the fate of carbon from thawing permafrost. To complement observational studies, this paper uses a numerical model to better understand variability in shelf sediment transport over timescales of hours to months. Specifically, a coupled hydrodynamic – sediment transport model, the Regional Ocean Modeling System (ROMS) - Community Sediment Transport Modeling System (CSTMS), is implemented within the Coupled Ocean-Atmosphere-Wave-Sediment Transport (COAWST) Modeling System, for the 2019 open water (nearly ice-free) season on the Alaskan Beaufort Sea shelf. Results showed that wave- and current-induced bed shear stresses frequently exceeded the critical stress for erosion and caused resuspension. Waves dominated bed shear stresses in depths shallower than 10 m and currents dominated in depths deeper than 20 m. Suspended sediment concentrations were highest during energetic wave events, although time periods with fast currents also caused resuspension, especially on the mid-to-outer shelf. When averaged over the open water season, modeled suspended sediment fluxes were westward, despite prevailing eastward currents, because of events characterized by fast westward currents. We expect these events may become more important for future sediment fluxes as storm frequency is projected to increase. Overall, the results improve our understanding of how sediment dynamics vary on the Beaufort Sea shelf during the open water season and provide insight into shelves characterized by strong currents and wave-induced resuspension.