UC Davis research at Slide Ranch
If you look out to sea from Slide Ranch on a clear day, you can see the peaks of the Farallon Islands roughly 25 miles offshore. In between lie the waters known as the Gulf of the Farallones, a dynamic seascape bustling with both marine life and vessel traffic that is protected as part of the Greater Farallones National Marine Sanctuary. Within this region, tides, seasonal storms and river outflows, and large-scale ocean currents all affect water movement, with implications for humans and wildlife alike. Through a partnership with the UC Davis Bodega Marine Laboratory, Slide Ranch houses a high frequency radar instrument, part of a national ocean observing network that continuously monitors ocean surface currents.
Using radar to observe ocean currents might sound like science-fiction, but the basic physics principles on which it operates can be easily understood. Imagine a car driving along Highway 1 passes a parked highway patrol officer monitoring traffic with a radar scanner. This device emits a burst of radio waves, which are reflected off the passing vehicle and detected by a receiver in the scanner. The time it takes for the reflected pulse to travel from the car to the scanner is slightly longer than the time it took for the transmitted pulse to reach the car. Based on this difference and the known properties of the radio wave, it is possible to compute the speed of the car relative to the scanner
Ocean observing radar functions similarly by transmitting radio waves from a stationary source on the shore, which are then reflected off ocean waves. If an ocean wave is moving away from the radar instrument, the return time will be longer than the transmit time – if it is moving towards the radar, the opposite will be true. Ocean observing radar operate continuously, and their internal software averages wave velocities over time and space to determine which direction and how fast the underlying ocean surface currents are moving.
Being able to observe ocean surface currents in near-real time has many applications – tracking the spread of oil spills, demonstrating the connection between the Gulf of the Farallones and the waters to the north, and search-and-rescue operations are all examples of things that have been done using data from ocean observing radar. Thanks to the collaboration between Slide Ranch and the Bodega Marine Laboratory, scientists, policymakers, and anyone interested in the state of the ocean can make use of high frequency radar data to learn about the Gulf of the Farallones. To learn more about ocean observing radar at Slide Ranch and beyond, you can visit the Bodega Ocean Observing Node webpage.
