The western coastline of Alaska is highly susceptible to coastal storms, which can cause coastal erosion, flooding, and have other pernicious effects to the environment and commercial efforts. The reduction in ice coverage due to climate change could potentially increase the frequency and degree of coastal flooding and erosion. Further, estuaries and delta systems act as conduits for storm surges, so when there is less nearshore ice coverage, these systems could introduce storm surge into terrestrial environments unaccustomed to saline intrusion, flooding, or other alien biogeochemical factors.
This project quantified the effect of reduced nearshore ice coverage on coastal flooding. The project developed a large domain tide, wave and storm surge model (SWAN/WWIII + ADCIRC) for the Gulf of Alaska and Bering, Chukchi, and Beaufort Seas, with high resolution along the Western Alaska coast. This computational model was assessed using historical wind/pressure fields and station observation data and captured the complex multi-scale and interactive physics of the deep water, shelf, nearshore, coast, estuaries, and rivers, and is more robust operationally. The model’s tidal solution was validated at 115 NOAA stations along the Alaska coastline for the 8 dominant astronomical tidal components and performed extremely well (R2 > 0.948 for the major semidiurnal phases, >0.945 for the amplitudes). Simulations of summer storms (ice free) predicted maximum surges within 5.5 cm of those recorded at Nome and Red Dog dock. The model did not perform as well for stronger winter storms with ice coverage, though performance was adequate to reveal that the presence of high ice coverage (>90%) may decrease the amount of surge only slightly.