Continuous Seep Monitoring at the Northern Cascadia Margin by Ocean Networks Canada

Since 2012 Ocean Networks Canada (ONC) has acquired high-quality long-term multibeam sonar data from the seafloor at Clayoquot Slope off Vancouver Island which is one of the most active methane vent regions of the Cascadia Margin, and where ONC has one of its nodes of the NEPTUNE cabled seafloor observatory. The sonar was first deployed at a vent field of irregular activity (near Bubbly Gulch), and since 2014 it is located at an extremely active field (Gastown Alley). The data that have been analyzed so far exhibit the strong dependence of gas bubble emissions with tidal pressure, although the tides alone cannot explain all the observed dynamics such as onset cessation of ebullition or periods of strong versus absence of seepage, and other factors need to be considered and ideally monitored to predict future seepage.

Seafloor cabled observatories are ideal to acquire high-resolution data of many ocean and seafloor parameters, including those from high-bandwidth data or power-intensive instruments. This presentation is an opportunity to explore possibilities to modify the existing seepage observatory, adding to the already installed instruments at Clayoquot Slope, or change focus to Barkley Canyon, another ONC node location, where hydrate mounts and outcrops occur and methane vents also exist.