Image: Installing radar at the FORCE facility on September 28, 2020
Usually, marine radar is adjusted to filter out sea clutter to avoid missing buoys and vessels.
But radar research at FORCE is doing the exact opposite: by focusing on sea clutter – things like waves and eddies – scientists are able to measure the velocity of the tidal flow in the Minas Passage.
“Radar operates similar to a space satellite,” says Dr. Joel Culina, FORCE’s physical oceanographer, and a leading expert in hydrodynamics in the Bay of Fundy. “It’s just bouncing its signal off the water, in extremely high detail. It bounces off moving waves, and from that you can determine the velocity of the tide. And as we gather more radar images, the quality of the velocity data gets better and better.”
“Using the radar, we see the surface waves quite clearly,” says Jeremy Locke, a research scientist at FORCE. “And we know wave properties – like frequency, and wave number – behave differently as the water speed changes. So, as Joel said, if we measure the waves, we can estimate the velocity of the tide.”
The radar project began as a way to capture velocity data to support tidal turbine site selection and operation. But new radar installations are opening up additional lines of research.
“Before, we were only focused on flow data to measure energy potential. Now we’re taking flow data and asking ‘How does it affect how fish move through the Minas Passage?’ It can provide us with a picture we’ve never seen before,” says Culina.
As part of the risk assessment program (RAP), Dr. Culina, together with Locke and field engineer Surinder Singh, are building an expanded radar network. This significantly upgrades existing flow data to deliver real-time hydrographic mapping of currents, eddies, and waves – all important determinants of fish distribution.
Culina adds: “There are unique features in the flow-field: for example, during the flow tide, the flow separates off Cape Split and produces huge eddies. On an ebb tide, a giant wake appears behind Black Rock. These are all things we can measure with the radar, in high resolution, that are going to affect fish distribution.”
When new radar data is combined with fish-tagging data, researchers will be able to create an accurate picture of where fish are in the Minas Passage, and the probability that they may encounter a tidal device.
RAP is funded in part by the Government of Canada and the Province of Nova Scotia. Key partners include Acadia University, Fundy Ocean Research Centre for Energy (FORCE), Marine Renewables Canada (MRC), Mi’kmaw Conservation Group (MCG), Confederacy of Mainland Mi’kmaq, Ocean Tracking Network (OTN), and Dalhousie University. Read more about RAP here.