radar antennas in wainwright

 

Chukchi Sea Surface Currents




How do we measure surface currents?

Believe it or not, it is possible to measure surface currents from the shore without having to get on a boat. This is made possible by a high-frequency radar system manufactured by CODAR Ocean Sensors, which consists of setting up two antennas on the shoreline. If you're local to Barrow, Wainwright, or Point Lay, you may have already seen the antennas. One of those antennas is a transmit antenna, and one is a receive antenna.

antennas
On the left is the transmit antenna, and on the right is the receive antenna.

The transmit antenna sends out a 5 MHz signal out over the surface of the ocean, and the receive antenna collects the signal that is bounced back by the ocean waves. This means that we have to have waves in order for the system to collect data. If there isn't any wind generating big waves, then we cannot measure the ocean currents, and there are only a few arrows on our map.

theory

The antennas must be placed at least 200 feet away from each other so that their signals do not cause interference. The received signal is shifted by a process known as the Doppler effect. This same principal is used by a policeman with his radar gun that can tell how fast you are driving. Knowing the amount of Doppler shift tells us how fast the currents are moving offshore. The movie below shows how two field sites interact with each other and what the radar sounds like, so make sure you have your sound turned on.

hfr_mpg