Impact of river run-off on global ocean mass redistribution

The impact of river run-off on global ocean mass redistribution is analysed by means of simulations with the baroclinic general circulation model OMCT driven by real-time atmospheric forcing fields from the European Centre for Medium Range Weather Forecasts (ECMWF). River run-off data have been deduced from a Hydrological Discharge Model (HDM) forced with ECMWF data as well. While submonthly mass variability is generally insignificant for GRACE de-aliasing purposes in most oceanic regions, monthly mean mass signals of up to 2 hPa occur in the Arctic Ocean during the melt season. Additionally, from freshwater fluxes due to precipitation, evaporation and river run-off the seasonal variations of total ocean mass are calculated. Correspondence with observed mass variations deduced from monthly GRACE gravity solutions indicates that a combination of ECMWF, HDM and OMCT allows a consistent prognostic simulation of mass exchanges among the atmosphere, ocean and continental hydrosphere. Thus, interpretations of GRACE based mass anomalies should account for both regional and global river run-off effects.