Deploying an Argo floating profiler. These floats are battery-powered and neutrally buoyant so they can drift at depth. Every 10 days, the floats rise to the surface while measuring temperature and salinity. When they reach the surface, the floats transmit these data to satellites, which determine their position. The floats then sink and drift until the cycle repeats. A float's life span is about 150 such cycles or about four years.