Ocean Color Reveals Sand Ridge Morphology on the West Florida Shelf

Inner shelf sand ridges are common features along many sandy coastlines. Here, I demonstrate that ocean color imagery from the operational satellite instrument Moderate Resolution Imaging Spectroradiometer can clearly show their morphology, including orientation, width, length, spacing, thickness, and distribution, on the inner west Florida shelf between the Big Bend and the Florida Bight (about 500 km N-S) up to 35-m water depth and 150 km from the shoreline. Some of the sand ridges were previously unknown due to lack of in situ data. Most of the periodic, parallel, and static features agree well with the existing high-resolution bathymetry. However, there are also mismatches between the bathymetric features and those revealed by the consistent satellite measurements, suggesting possible errors in the bathymetry data. Using a simple optical model, I show that the 500-m resolution imagery can accurately reveal sand ridge thickness from several meters to < 1 m. Because of the repeated and synoptic coverage, these medium-resolution ocean color imageries provide unprecedented capability in studying distributions and changes of the sand ridge morphology, which are otherwise expensive and difficult to obtain.