Research Seminar – John Malito

The UNC-CH Department of Marine Sciences presents a research seminar from graduate student, John Malito. This event will be held on Monday, October 19th, at 12:00 pm. However, this seminar is remote only and can be viewed online via Zoom (Meeting ID: 974 6573 2747).

Seminar Title: How Arctic continental shelves may respond to climate-driven changes in sediment supply and sea states

Abstract: Polar coastal environments, including the Alaskan Beaufort Shelf (ABS), are experiencing rapid declines in sea ice coverage and duration, increasingly energetic sea states, and accelerating coastal retreat. Morphological feedbacks between the shelf and the coastline will likely play an important role in future hydrodynamic and sediment transport regimes of ice-dominated shelves. This study will evaluate the evolution of the ABS given expected increases in wave energy related to declining sea ice coverage and increases in fluvial sediment supply and coastal erosion. A stable 2DV cross-shelf model has been developed in Delft3D using Beaufort shelf bathymetry, representative tides and wind derived from multi-decadal records, and wave parameters scaled to represent morphodynamically significant waves. Two 1000-year trials were conducted using two 20-year wave records (1979–1997 and 1997–2017) in order to evaluate the sensitivity of the shelf to wave climates with a 21% difference in steepness. In both cases, the modeled shelf attained dynamic equilibrium within 300 years, characterized by stable morphologic changes on the order of millimeters per 100 years. Wave induced onshore-directed sediment fluxes shaped the shelf profile and produced a sigmoidal profile with a convex-upward offshore depocenter transitioning into a concave-up nearshore and shoreface. We find that the shelf is sensitive to changes in wave conditions. At depths >10 m, moderate waves generated 0.02-0.72 m of bed erosion, and steeper waves generated 0.03-0.89 m of bed erosion over a 1000-yr timescale. Wind shear stresses produced setup and setdown at the shoreline on the order of tens of centimeters, with resultant downwelling and upwelling currents near the seabed producing erosion and accretion, respectively, at depths between 20 m and 40 m. These initial trials will serve as a foundation for testing the effects of changing sediment inputs and hydrodynamic regimes expected in the rapidly warming Arctic.