Sediment accretion in a lower-energetic location during two consecutive cold fronts

ABSTRACT During the passage of two consecutive atmospheric cold fronts that migrated eastward along the northern Gulf of Mexico, currents, waves, and seafloor elevation were observed from instrumentation attached to a metal structure called ‘quadpod’ at the 7.5 m bathymetric contour off the coast of Panama City, Florida. During the passage of the first front, significant wave height (Hs) increased from 0.15 m to 1.2 m, and seafloor elevation relative to the quadpod increased by up to 5 cm at the quadpod location. During the passage of the second front, Hs peaked at 2 m, and seafloor elevation increased by up to 15 cm over 24 h. The increase in the seafloor elevation is consistent with the burial of surrogate munitions observed with sonar imagery and with sediment accretion from a Delft3D simulation. The model predicts cross-shore seafloor changes with erosion nearshore and accretion offshore, starting at approximately 250 m from the coast. The seafloor elevation increase is attributed to sediment accretion driven by wave forcing. The results of this study have important implications for morphological changes and object burial during a period of front-driven waves in the northern Gulf of Mexico, which is typically a lower energetic environment.