A Subbottom Profiler Survey of the Upper Monterey Canyon Using the MBARI Mapping AUV

During the Spring and Summer of 2004, MBARI conducted subbottom profile surveys across the main, active channel of the upper Monterey Canyon and two northward trending sub-canyons that appear in swath bathymetry mapping to be mostly filled by recent sediments. Monterey Canyon is the dominant submarine physiographic feature of the Monterey Bay region, and serves as the primary conduit for sediment transport from the coast and shelf to the deep ocean seafloor. These surveys were conducted during the initial sea tests of the new MBARI Mapping Autonomous Underwater Vehicle (AUV). The data were collected using an Edgetech FS-AU 2-16 kHz sweep Chirp subbottom profiler operated on the AUV at vehicle depths up to 250 m. Navigation and attitude data derived from an inertial navigation system (INS) incorporating a ring laser gyro and a 300 kHz Doppler velocity log (DVL). Good subbottom data, with typical penetrations of 0.05 seconds, were collected along 140 km of profiles covering an area roughly 3.6 km east-west by 8 km north-south. The profiles clearly show that a single, stratigraphically uninterrupted deposit of sediments has in fact filled the northward sub-canyons. Profiles crossing the main channel also reveal remnants of previous sediment infill along the canyon walls, suggesting that the entire upper Monterey Canyon may have once been filled by sediments as much as 100 m thick.