“Green” glider

The Slocum glider is an autonomous vehicle that moves up and down in the ocean by changing buoyancy, using only heat energy from the ocean. The torpedo-shaped vehicle, measuring 2 meters (6.5-feet) long, descends to about 5,000 feet (1.5 kilometers) and then rises back to the surface about 2.75 miles (5 kilometers) farther on, tracing a regular roller-coaster pattern in the ocean. As it ascends sensors in the glider’s bow measure water temperature and salinity. At the surface, the glider reports its position and transmits data via satellite. Scientists can also transmit commands, redirecting the glider on a new route, for example. The glider was named for Joshua Slocum, the first man to sail around the world alone, and for his boat.

(Photo by Paul Fucile, Woods Hole Oceanographic Institution)