Impact of Argo, SST, and altimeter data on an eddy‐resolving ocean reanalysis

We perform a series of Observing System Experiments (OSEs), where components of the Global Ocean Observing System (GOOS) are systematically withheld from a data assimilating ocean reanalysis. We assess the relative importance of Argo temperature (T) and salinity (S) profiles, sea‐surface temperature (SST) and altimetric sea‐level anomalies (SLA) for constraining upper‐ocean T and S properties and mesoscale variability of SLA in an eddy resolving ocean reanalysis in the Australian region. Each OSE is assessed by comparing modelled fields with assimilated and withheld observations. We show that each observation type brings complementary information to the GOOS, and demonstrate that while there is some redundancy for representing broad‐scale circulation, mesoscale circulation requires all observation types to be assimilated.