Exploratory Data Analyses on Deep-Sea Side-Scan Sonar Data in the Northern Pacific Ocean: Implication on Interactions between Sedimentation and Bottom Currents

We elicit various geologic information from the seafloor, including topographic changes due to the past plate movement, climate change, and submarine volcanic activities. Useful mineral resources such as manganese nodules are also littered on the seafloor. Since 1992, Korea Institute of Ocean Science and Technology (KIOST) has conducted multidisciplinary cruises to examine minability of deep-sea mineral resources and its environmental effects at the Clarion-Clipperton Fracture Zone, northern Pacific Ocean. As continuing scientific efforts, KIOST utilized the IMI120 deep tow system configured to collect 4-kHz SBP data along with seabed imagery in 2010. In this study, thus, we compare the deep-tow side-scan sonar (IMI120) acoustic measurements with sub-bottom profiler (SBP) data in order to explore statistical relations, if any, between these different acoustic data. While deep-sea imagery data are useful for understanding acoustic characteristics of the ocean floor, SBP data image geologic stratification of the seafloor. First, we identified transparent layers from the SBP data by applying bottom-hat transformation to the SBP images in order to isolate effectively the transparent layers from the noisy background. Then, we compared the thickness variation of the identified transparent layers with the IMI120 side-scan intensity. The spatial distribution of the transparent layers in the study area appears to be correlate with the topographic changes, which may be interfere with the bottom currents in the Pacific Ocean. This interaction would have enhanced sedimentation at the areas with thick transparent layers.