Increasing Wave Energy Moves Arctic Continental Shelves Toward a New Future

Abstract

Arctic continental shelves, including the Alaskan Beaufort Shelf (ABS), are experiencing declines in sea ice coverage leading to increasingly energetic sea states and coastal erosion. In this study we investigated the morphologic response of the ABS to increasing wave energy, and how shelf profile adjustments modify wave energy propagating toward the coast. We developed a 2D cross-shelf morphodynamic model using Delft3D and tested shelf response to a present-day wave climate and a future Arctic wave climate projected under the RCP8.5 climate-change scenario. Simulations lasting 1000 years were conducted for relatively steep (Flaxman Island, AK, slope 0.0008) and flat (Harrison Bay, AK, slope 0.0003) cross-shelf profiles. We found that morphologic evolution and regulation of future waves depends primarily on existing shelf morphology. On the steeper profile, RCP 8.5 waves drove sediment erosion at 0–15 m water depth and redeposition at 15–30 m water depth. Over 1000 years, this redistribution of sediment from the inner to middle shelf resulted in a 7.6% reduction in wave heights at the 2 m isobath. This morphologic adjustment represented a regulatory feedback in which shallowing of the middle shelf led to attenuation of waves reaching the inner shelf. In contrast, effective wave attenuation across the flatter and wider Harrison Bay section limited cross-shelf transport and morphologic change under both wave climates. Together our results suggest that coastal changes in response to the growing Arctic wave climate may be dependent on shelf morphology, and even mitigated in some regions by morphologic adjustment.