Ocean-sensor project reaches milestone

Scientists seeking to deploy an armada of 3,000 robotic probes to take the pulse of Earth’s oceans are halfway to their goal.

As of Nov. 30, 2004 oceanographers had launched 1,516 of the sensor-laden Argo floats, says project director John Gould of the Scripps Institution of Oceanography in La Jolla, Calif. Those probes, each costing about $15,000, measure temperature, salinity, and other water characteristics in the uppermost layers of the ocean (SN: 2/1/03, p. 75: Available to subscribers at Electronic Jetsam). Each device is programmed to sink to a depth of 2,000 meters, drift with ocean currents for 10 days, and then collect data as it bobs back to the surface. In general, a float’s data are available on the Internet within 24 hours of the time of transmission.

Collectively, the probes gather about 50,000 ocean-column profiles each year, says Gould. Recent deployments of Argo floats in the South Pacific have plugged data gaps from that area. The full array of 3,000 Argo probes should be in place by 2007.

Eighteen nations—including the United States, Japan, France, Australia, and the United Kingdom—have purchased floats for the network. Scientists at 12 ocean- and climate-research centers around the world currently use Argo data in their analyses and forecasts.