Water Column Sampling Capabilities of the NEPTUNE Canada Regional Cabled Observatory

The NEPTUNE Canada Regional Observatory affords a wide range of opportunities to conduct adaptive and high-temporal resolution water column property studies. Intensive sites are located in a shallow near-shore environment (Folger Passage), a shelf-slope-break region (Barkley Upper Slope) and a deep offshore mid-ocean spreading centre (Endeavour Ridge). The Folger Passage site has instrument platforms at 100 m and 23 m which are located near the mouth of Barkley Sound on the west coast of Vancouver Island. Instruments include upward-looking surface-wave resolving Acoustic Doppler Current Profilers (ADCPs), multi-frequency echo-sounders to measure backscatter from zooplankton and bottom pressure recorders to assess long-wave variability (e.g. tsunami, shelf waves, tidal). The near-bottom water column is sampled for salinity, temperature, oxygen, chlorophyll, turbidity, photosynthetically active light and, in addition, there are fine scale measurements of the velocity structure of the bottom-boundary layer. Water column measurements at the 400 metre deep Barkley Upper Slope site are facilitated by a world leading Vertical Profiling System (VPS). This winch operated system will profile a suite of instruments through the water column at up to 4 cycles per day. Optical measurements consist of a pair of hyperspectral radiometers to characterise downwelling irradiation and upwelling radiance, backscatter fluorescence for chlorophyll, and an optode to determine oxygen levels. A pumped CTD will provide salinity, temperature, depth as well as plumbing for a nitrate sensor, a coloured dissolved organic matter sensor and a pCO2 sensor. Acoustic instruments on the profiler consist of a 400 kHz ADCP, 200 kHz echosounder and a broad band hydrophone. With these instruments we expect to be able to explore the covariation of physical and chemical parameters with impact at a range of trophic levels, up to and including marine mammals. At the base of the VPS there is a long range ADCP to monitor velocity structure throughout the water column as well as a near bottom CTD and bottom pressure recorder. At Endeavour Ridge the first of four sub-surface taught-line moorings will be placed in fall 2010. These cable-connected moorings carry CTD / acoustic current meter mooring pairs at 3, 50, 125, and 200 metres above bottom. At the top of the mooring there is an upward-looking long-range ADCP which can penetrate to ~800mab, about 1300m depth nearing the bottom of the mid-depth scattering layer. Here again there is a bottom pressure recorder to gauge large scale barotropic motions. With these moorings we expect to explore the relationships among rough bathymetry generating a complex circulation structure, the fluid/thermal fluxes from hydrothermal venting and the unique ecology of the region. These three intensive sites fit into a larger matrix of water column sampling in the northeast Pacific to provide long term high-temporal resolution as well as adaptive response to episodic events.