News from VENUS
by Mark Halverson (University of British Columbia)
Fig. 1. Photograph of the plume edge in summer (photo credit: Kevin Bartlett).
The Fraser River reaches the ocean near Vancouver, and there the fresh water it carries mixes with ocean water to form a thin plume of buoyant brackish water, which according to one oceanographer is the “showpiece of the Strait of Georgia.”
Oceanographers have been studying the Fraser River plume since at least the 1960s, but more recently, VENUS has installed a radar system to measure the surface currents in this region. Furthermore, VENUS has also installed the Seakeeper seawater monitoring system on the BC Ferries MV Queen of Alberni to collect detailed information of water properties along the Duke Point – Tsawwassen ferry route which cuts through the plume eight times per day. These new observations, coupled with satellite imagery, are being used by UBC researchers Dr. Mark Halverson and Prof. Rich Pawlowicz to reveal the nature of the Fraser plume. The research is being carried out as part of the Marine Environmental Observation Prediction and Response Network (MEOPAR), which is tasked with improving Canada’s ability to respond to marine hazards.
In the early summer when the Fraser River carries high sediment loads, the plume is easy to distinguish from ocean water by its distinct light brown colour (Fig. 1). It can be highly reflective and opaque to sunlight, and because it is a mixture of river and ocean water, it can be quite “fresh.” A comparison of the measured surface currents to both surface water salinity and satellite imagery shows that a jet of swiftly flowing water can form near low tide (Fig. 2).
A sharp change in the currents occurs where the ocean colour and salinity change rapidly, signifying the edge of the plume. As the plume waters move away from the river mouth, it appears that the wind ultimately determines its fate. During northwesterly winds, the plume is driven to the south, while during southeasterly winds, it is driven to the northwest (Fig. 3). However, the relative importance of the wind might change when the river flow is much higher. Ultimately, researchers hope that a better understanding of the surface currents in this area will be useful to emergency response operations by providing a way to anticipate the trajectory of, for example, spilled oil or other contaminants.
Fig. 2: Combined satellite image and surface current map. The light region denotes the plume, and it corresponds to a region sediment rich, reflective, low salinity water. The red line shows the track of the BC Ferries M/V Queen of Alberni.
Fig. 3: Predicted trajectories of objects released at the river mouth. The small inset graph shows the wind direction and speed. In this case the wind is blowing from the northwest.
After three years of planning, design and construction, the Buoy Profiling System (BPS) is now ready to be installed. On Aug 1, the Saanich Inlet-destined 7-m wide buoy structure was successfully launched in Patricia Bay. The next step is to secure the buoy in place 4 km south of the Node using a triple mooring, and the connection of the system to the VENUS Node in Saanich Inlet via a specialized power and communications cable. The buoy is presently tied to the wharf at the Institute of Ocean Sciences (IOS) undergoing final inspections and testing, and will be relocated to the centre of Saanich Inlet at the end of August, where it will routinely profile the seasonally anoxic waters in Saanich Inlet using standard and customized instrumentation.
In the image
Buoy Profiling System launch. Patricia Bay, Saanich Inlet. August 1, 2013.
: Buoy Profiling System is being towed to the IOS dock for final testing; Paul Macoun aboard the buoy.
Map of the VENUS observatory.
“Integration of ocean gliders into the ONC observatories is progressing”, advised Paul Macoun – Project Manager of the VENUS Phase II developments. Presently, the engineering team is working up the first of two gliders for deployment off-shore this summer.
“The science community is eagerly waiting for the new system to be available to conduct research in the water column”, confirmed ONC Associate Director of Science Dr. Richard Dewey. After initial testing in Saanich Inlet in July, the glider will have a full field trial in August off the west coast of Vancouver island linking water properties between Barkley Canyon and Barkley Sound”.
In the image: Rowan Fox, a technician working for Dr. Jody Klymak, UVic SEOS, assists VENUS engineers to conduct buoyancy testing at the Marine Technology Centre.
|G2 Slocum Electric glider specifications:
||0.4 m/sec horizontal average
||Typically 30 days, depending on measurements and communication
||GPS, magnetic compass, altimeter, subsurface dead reckoning
||CTD and oxygen
||RF modem, Iridium satellite, ARGOS, Telesonar modem
For more details visit Teledyne Webb Research.
The VENUS team will be at sea between April 28 – May 7 for another maintenance and installation cruise.
Live Data applets on the homepage, video streams and data plots will not update regularly during this time. Some data may be unavailable from the VENUS Download Data page.
The team plans to:
- Recover and redeploy instrument systems in Saanich Inlet.
- Re-install the Delta Dynamics Laboratory platform in Strait of Georgia at 110m.
- Add the Seismic Liquefaction In-situ Penetrometer (SLIP) to the Delta Dynamics study area.
- Install new sensors and systems developed by ONCCEE at the Delta Dynamics and Strait of Georgia East study areas.
- Re-install the DFO’s Institute of Ocean Sciences Hydrophone array at Strait of Georgia East 170m.
- Deploy the Bottom Boundary Layer experiment in the Strait of Georgia Central 300m study area.
Due to the number of platforms being deployed during this cruise, it will take the ONC Data team more time to update all the data services on the VENUS website.
To follow the cruise and receive up to date information visit the dedicated website: Wiring the Abyss 2013
VENUS has released new and improved data products for stationary platforms:
* NEW: For all Seabird CTDs, we are now offering a selection of TEOS-10 variables including Absolute Salinity, Conservative Temperature, InSitu Density from Conservative Temperature and Sigma0 from Conservative Temperature. For more information on TEOS-10, please see http://www.teos-10.org/.
* NEW: For oxygen variables, we are now offering the calculated variables oxygen saturation and apparent oxygen utilization for devices that are piggybacked onto a Seabird CTD.
* IMPROVED: To address user requests regarding the date format in our csv files, we have changed the format from decimal day to IOS-8601 format. The new date format is of the form yyyy-mm-ddTHH:MM:SS.FFF.
Visit the Download Data page to try the new products.
Responding to a failure of an array power connector on the Strait of Georgia array of VENUS in early fall 2012, a joint team of engineers from ONC and OceanWorks Int'l have spent a week (Feb 5-9) aboard CS Wave Venture recovering, repairing, testing and redeploying the VENUS primary sub-sea infrastructure in the Strait of Georgia.
The marine operation was a challenging procedure for the cable ship but proceeded smoothly without any major complications. The repair coincided with the 7th anniversary of operations for the VENUS network which began in 8 February 2006.
“The mission was a success”, reported Adrian Round, Director of Observatory Operations (ONC). “Both nodes were recovered, upgraded with new Junction Cans and connectors and redeployed to the original sites in the Strait. The next step is to re-deploy all the science instrument platforms, which is scheduled for late February”.
This month VENUS celebrates its 7-th Anniversary, on 8 February 2006 it is exactly seven years since the first node on the VENUS seafloor network was put into place at the bottom of the Saanich Inlet. It was the beginning of the journey in which science and engineering combined to undertake the challenging mission of building an advanced cabled ocean observatory, which is now a reality.
We have come a long way and would like to thank the dedicated staff and scientists who have been actively participating in the development of what is now the coastal network of Ocean Networks Canada.
With our core installations, the new components of VENUS Phase II, and now our integration with NEPTUNE, we look forward to another decade or more of collaborative ocean exploration.
The Birth of VENUS was marked by the University of Victoria as one of the greatest moments in the history of the university. Read the recollection of the founding director of VENUS – Dr. Verena Tunnicliffe on the UVic website.
Buoy Profiling System (BPS) Winch Test Progress. (January 2013)
The VENUS BPS winch system test on the OTTB Buoy is progressing. Soon after installation in December 2012, the system underwent a site acceptance test with the manufacturer. Following on from this, the Data Management group has now developed a real time linkage between the system and the database. The next stage is to develop the software infrastructure to command and control the system.
The picture shows the instrument cage (centre) being lowered into position under the winch (centre left). An engineer from MacArtney A/S (next to winch in blue) was on site at this time to conduct the site acceptance test. VENUS engineer Paul Macoun (in red) is spooling in winch cable to take up slack as the OTTB crane is lowered.
We anticipate that the software development will be complete by the end of February 2013, at which time the system will come off the OTTB buoy. The next step will be integration with the custom-built buoy at the Marine Technology Centre.
See Buoy Profiling System (BPS) on the map of the VENUS Saanich Inlet array.