This computation involved: Reading University Ocean Reanalysis Software deployed on Reading University computer. Reading University developed ocean reanalysis software which uses the NEMOv3.2 ocean model in configuration ORCA025_LIM (1/4 deg by 75 vertical levels). The model is forced with ECMWF ERA-Interim atmospheric reanalysis without corrections for radiation and precipitation and bulk fluxes calculated as in Large and Yeager (2004). The vertical grid has 75 levels with partial steps at the bottom. The data assimilation methodology is similar to what is currently employed in the UK Met Office operational FOAM - NEMO system (Storkey et al., 2010). It is an OI-type scheme with assimilation increments calculated using a first-guess-at-appropriate- time (FGAT) scheme every 5 days and introduced evenly over the period in an incremental analysis update (IAU) step. UR025.4 assimilates in situ and satellite-based SSTs, altimeter SLA from AVISO/CLS using the Rio et al. (2005) mean dynamic topography (MDT), in situ temperature and salinity profile observations obtained from the UK Met Office ENACT/ENSEMBLES (EN3_v2a_NoCWT_LevitusXBTMBT_ Corr) data set, which includes bias corrections for XBT and MDT data, and satellite-based sea ice concentrations from the EUMETSAT Ocean Sea Ice Satellite Application Facility (OSI-SAF).