Argo

Argo is an international array of autonomous profiling floats that measures temperature and salinity through the upper 2,000 meters of the ocean. Its freely available observations support ocean research and climate monitoring.

Argo float: An autonomous ocean instrument that changes buoyancy to profile water properties and transmit observations by satellite. Each Argo float repeatedly descends, drifts at depth, and rises to measure a vertical ocean profile.
Ocean heat content: The thermal energy stored in the ocean, commonly estimated from temperature profiles over depth. Argo observations reveal how much heat the upper ocean absorbs and stores.
Global Ocean Observing System: An international framework coordinating sustained observations of the global ocean. Argo is one component of the broader system for observing ocean conditions.
Practical salinity: A dimensionless measure of seawater salt content inferred from conductivity relative to a standard reference. Argo’s conductivity observations are converted into practical salinity values.
Conductivity–temperature–depth profiler: An instrument that measures seawater conductivity, temperature, and pressure to derive salinity and depth. Argo floats use CTD sensors to collect the core measurements in each profile.
Ocean salinity: The concentration of dissolved salts in seawater, varying with evaporation, precipitation, and freshwater inputs. Argo measures salinity alongside temperature to track changes in ocean freshwater content.
World Ocean Circulation Experiment: An international research program from 1990 to 2002 that studied large-scale ocean circulation and climate. WOCE’s hydrographic surveys helped establish the observational foundation and goals that Argo extended.
Potential temperature: The temperature a water parcel would have if brought adiabatically to a reference pressure. Ocean profiles often use potential temperature to compare water masses at different depths.
Lagrangian drifter: A floating instrument that moves with surface currents while recording position or ocean conditions. Unlike surface drifters, Argo floats spend most of their cycle at depth before profiling upward.
Ocean reanalysis: A consistent reconstruction of past ocean conditions produced by combining observations with a numerical model. Argo profiles constrain reanalyses of the changing ocean state.

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