Reanalysis (Ocean)

Ocean reanalysis reconstructs the past ocean state by assimilating historical observations into an ocean model run over decades, producing a dynamically consistent gridded record of temperature, salinity, currents, sea level, and sea ice. It blends satellite altimetry and sea-surface temperature with in-situ Argo, XBT, and mooring profiles through schemes such as 3D-Var, 4D-Var, or ensemble Kalman filters, filling the gaps the observing network leaves. Products such as GLORYS, ECMWF ORAS5, and the SODA series serve climate research, current and heat-content trends, and as reference fields for forecast verification and weather-routing hindcasts. Accuracy improves sharply after the Argo array matured around 2005.