Summary:
Geophysical methods are key in the characterization of physical systems. This project applies two key geophysical methods to the Alabama continental shelf:
1. Seismic reflection to characterize the water column
2. Sidescan to characterize the seafloor of the Alabama continental shelf
Seismic reflection, though typically used to image below the seafloor, can also be applied to the water column. Salinity boundaries within the water column create acoustic impendence boundaries, which will reflect energy in the same way that contrasting rock layers do. The resulting images illuminate the temperature-salinity structure of the water column and provide essential constraints to physical models of water circulation. Sidescan imagery is used to constrain seafloor lithology without physical sampling.
The lithology of the seafloor is important in determining how fluids (and hence pollutants such as oil) are transmitted into the rocks and sediments on the seafloor. Biologists are also interested in the nature of the seafloor due to the affinity of certain organisms for particular seafloor types. Sidescan sonar is a tool that is routinely used to map variations in seafloor acoustic reflectivity, which is directly related to seafloor texture and hence rock/sediment type. Modern interferometric sidescan systems such as HAWAII-MR1 allow determination of seafloor acoustic reflectivity with a dynamic range of over 1,000,000 and a horizontal resolution on the order of meters even in the deep ocean. Such systems allow the mapping of subtle variations in the seafloor type with high precision. Disturbed areas of the seafloor, as might be associated with gas seeps, can also be readily identified.