Argo is a system for observing temperature, salinity, and currents in the Earth's oceans which has been operational since the early 2000s. The real-time data it provides is used in climate and oceanographic research. A special research interest is to quantify the ocean heat content (OHC).Argo consists of a fleet of almost 4000 drifting profiling floats deployed worldwide. Each Argo float weighs 20–30 kg.