HF RADAR

Using HF radar, we can monitor the movement of ocean currents without ever leaving the coastline. This is made possible by a high-frequency radar (HF radar) system, built by CODAR Ocean Sensors, which uses two antennas installed along the coastline. If you’ve been near Utqiaġvik (Barrow) or Wainwright, you may have seen these antennas in the field. One is a transmit antenna that sends out a radio signal (around 5 MHz), and the other is a receive antenna that listens for the signal reflected back from ocean waves.

Here’s how it works: when the radar signal bounces off the surface waves, the frequency of the returned signal is shifted by the Doppler effect—the same principle a police radar gun uses to measure the speed of a car. By analyzing this frequency shift, we can determine the speed and direction of surface currents offshore.

HF radar systems need surface waves to function, so calm conditions can reduce the amount of data collected. When the wind picks up and waves grow, the system provides a continuous, high-resolution map of coastal currents, with antennas spaced at least 200 feet apart to avoid interference.

Together, the radar sites form a coastal observing network that provides critical information for understanding ocean circulation, search and rescue operations, oil spill response, ecosystem studies, and safe navigation in Alaska’s dynamic waters.

UAF HFR data is available in near-real time via the Integrated Ocean Observing System (IOOS) HF Radar Network.