WHOI Argo
The Argo Program, launched in 1999, is a global array of floating robots that collect information about the physical state of the upper ocean, including temperature and salinity. Argo has passed its initial target of 3000 floats worldwide, with around 4000 floats currently taking measurements.
The basic goal of Argo is to track where heat and salinity are changing across the global ocean, down to a depth of 2000 meters, and to send that information back to scientists and operational agencies in real time to help with climate and ocean prediction. Argo floats are not concentrated in shipping lanes, as are measurements from commercial or research vessels, and are able to collect data year-round.