A Long-Term Real Time Sea Bed Morphology Evolution System in the South Atlantic Bight

A long-term real time sea bed morphology monitoring system has been established on the middle continental shelf in the South Atlantic Bight. This constitutes part of the Southeast Coastal Ocean Observing System (SEACOOS) and now supports a project that focuses on studying material exchange processes in permeable sediments in response to large scale atmospheric and oceanic forcing. In particular the system supports studies of advective-pore water exchanges that depend on the size and geometry of the wave-induced ripples and the strength of the overlying flows. The seabed morphology system is composed of an Imagenex Model 881 tilted-head digital rotating imaging system (2.25 MHz) connected through 1.5 km of cable to a power and controller unit housed on the R2 Naval platform utilized by the South Atlantic Bight Synoptic Offshore Observational Network (SABSOON). The system collects acoustic images of the seabed along 6 meter long radials with resolution of 0.3 degrees. Data are acquired hourly, transmitted via microwave antenna to shore and reach the laboratory via T1 land line. Raw images are rectified and processed using a 2-dimensional Fast Fourier transform algorithm providing wavelength and ripple orientation values. Post-data collection image processing allows evidence of bioturbation to be identified as well. The long-term data base (since April 2007) is used for evaluation of time-dependent ripple evolution models. System design, data analysis methods and example images are presented. The long-term data are used to evaluate a recently introduce time-depended model for coarse sand ripple evolution.