Mapping Currents in the Coastal Ocean with Radio Waves

Satellites have difficulty returning data for the coastal area; the land echo is very strong and contaminates the signal from the water. Maps collected with high-frequency radio techniques provide the only data sets on ocean surface currents which are highly resolved in both space and time, yet can extend over many kilometers and be collected over long time periods.

Mike Kosro has installed high-frequency radio antennas and data recording equipment at several Oregon coastal locations. Each coastal site consists of two low-power radio antennas; one transmits and one receives.

The equipment measures ocean currents using the echoes of radio waves scattered continuously from ocean waves. The received radio waves are shifted in frequency by the combined effects of ocean waves and ocean currents. The known properties of the ocean waves are then subtracted, leaving the effects of the ocean currents. The system provides hourly maps of surface currents out to 25–100 miles from shore.

The circulation of coastal ocean currents can have profound impacts on fisheries, birds, man-made structures, search and rescue operations, and dispersal of pollutants. CIOSS is looking at ways to stitch together the coastal current measurements and the satellite data. The detailed maps also give data sets needed by modelers working on coastal dynamics.

Coverage of coastal waters by radio wave equipment on shore.