Coastal Multidisciplinary Dynamics Elucidated by a Vertical Profiler on the Upper Continental Slope off Vancouver Island, Canada

The NEPTUNE Observatory is a cabled network of seafloor oceanographic instruments in the Northeast Pacific operated by Ocean Networks Canada. Since 2009, there have been many deployments of a Vertical Profiler on the observatory on the upper slope of the continental margin. However there have been many challenges resulting in differing degrees of success and deployment lengths. Currently the profiler is in 400m of water since May of 2024 working on a reduced schedule to help ensure a full annual cycle. Prior to this deployment we’ve had two deployments that survived a significant portion of the year, in addition to shorter deployments.

 

The placement of the vertical profiler is at 400m depth down the slope of the nominally 200m deep shelf. The slope proceeds down to about 2000m passing a plate subduction zone and meeting the gently sloping Cascadia abyssal plain. The continental slope along the west coast of Canada and the US is heavily excised by canyons and we choose to strategically locate the deployment away from any canyons to remove canyon effects from the observations. Still, the circulation dynamics in the region are very complex. The surface waters are in the transition zone between the wind-driven currents associated with the Alaskan Gyre and California Current Systems. Deeper, the midwater is heavily influenced by the poleward flowing California Undercurrent which is then further modulated by remotely generated passage of coastal trapped waves. Being on the continental slope, the currents are also strongly influenced by the internal tide as well as shorter internal waves generated by the passage of the tides.

 

The currently deployed Vertical Profiler System (VPS) carries instruments to measure water properties, temperature salinity, oxygen, pCO2, pH, turbidity, fluorescence and upwelling radiance with some redundancy. In this study we put together observations from historic deployments along with the current real-time observations to develop an understanding of the physical coupling with the biogeochemistry, the long-term variability of the water properties as and the interdependencies of these variables. Finally, we delve into the complexities of obtaining water property measurements using this type of vertical profiling system.