Ocean Networks Canada Workshop: Seafloor collapse and submarine canyons

This month Ocean Networks Canada held a workshop in Victoria, BC focused on the “seabed and sediment in motion” at their observatory sites. They have cabled instruments on the seafloor that continually send data back to shore. The workshop focused on studies at two contrasting focus sites, one on the Fraser River delta, and the other in Barkley Canyon on the continental margin. Submarine canyons are dramatic features of continental margins throughout the world. They can be many kilometers deep and cut far into the shelf, like a Grand Canyon deep underwater. These canyons are hotspots of biological activity as well as conduits for sediment, nutrients, chemicals, and trash. Andrea Ogston attended the workshop to present collaborative research from Barkley Canyon and hear results from colleagues.

Map of a few of the instrumented ONC observatory sites in Barkley Canyon. Our margin off the west coast of the US/Canada is incised by numerous submarine canyons.

On the Fraser Delta, frequent mass failures of the seafloor and energetic gravity flows pose potential problems for the coastal port structures.  Dr. Gwyn Lintern, PGC, showed a dramatic data set from sensors that tumbled in a bottom flow recording velocities of 6-8 m/s, and eventually disconnected and disappeared!  In contrast, Barkley Canyon located off the coast of Vancouver Island has a very limited source of sediment at present, and dynamics are not as dramatic. However, Andrea Ogston showed two modes of particulate transport at ~1000 m water depth within the canyon axis:  1) relatively dense fine particles move down the canyon, carried by residual currents, and are at times pumped back up-canyon by tides, and 2) loose, fluffy phytodetritus (chunks of tiny organisms) from the surface ocean are mixed down into the canyon and during winter downwelling periods can be rapidly transferred to the deep ocean.  This winter process has the potential of adding significantly to the biological pump (which transports carbon to the deep sea). If you’re interested in reading more, check out Thomsen et al., 2017.

After a presentation and discussion of what can be done with the existing data on the Oceans Network Canada observatories, the workshop turned to needs and wants that could enable the next steps in the scientific discovery using the observatory data streams.  New, updated sensors and a reconfiguration of Barkley Canyon’s sensor array will be upcoming and will allow the scientific community to further explore the importance of the wintertime delivery of carbon to the deep sea.  Stay tuned for more on this exciting discovery!

Victoria BC at night during the ONC Seabed and Sediment in Motion Workshop