Spatial Relationship Between Methane Seeps and Geomorphological Properties of the Seafloor on the US Atlantic Margin

Abstract:

A growing body of research, based on acoustic detection of water column gas bubble plumes, indicates that seafloor methane seeps are a common feature on continental margins around the world. Results from recent methane seep detection efforts focused on the US Atlantic margin indicate the presence of approximately 648 gas seeps in a surveyed area of 145,200 km² that extends from Cape Canaveral, Florida to the US-Canadian maritime border. Preliminary analysis of bathymetric data and submersible observations suggests that the position of these seeps may be associated with specific geomorphological features on the continental margin such as the crests of inner-canyon ridges and current facing slopes. Here we present a quantitative analysis of the spatial relationship between gas seeps and seafloor geomorphic features on the US Atlantic margin. Specifically, we use the geomorphon (Jasiewicz & Stepinski, 2013) and bathymetric position index (Wright et al., 2005) approaches to quantitatively segment and classify seafloor geomorphic features based upon gridded bathymetric data. We then evaluate the strength of spatial relationships between methane seep locations and resultant geomorphic classes as well as measured seafloor slope angle and aspect. The results of this research hold the potential to enhance understanding of the geological and physical oceanographic processes that mediate gas release, provide insight into the non-uniform spatial distribution of the seeps along the margin, and better predict the location of seeps on margins that have not yet been surveyed. Understanding the processes that control seep distribution is important because seeps are a significant transport pathway in the global carbon cycle with implications for localized acidification, deoxygenation, biological productivity, and energy production.