Global Freshwater Fluxes into the World Oceans

Abstract

The Global Runoff Data Centre (GRDC) deploys the data product Global Freshwater Fluxes into the World Oceans since 1996. The quantification of freshwater fluxes into the ocean is an important link to oceanography and climatology, as the salinity of sea water influences ocean currents and is a driver of evaporation and therefore interconnects to the general circulation of the atmosphere. The first versions of the data product were based on runoff coefficient estimates for ungauged basins. Since 2004, results of the global hydrological model WaterGAP (AG Hydrologie, GoetheUniversität Frankfurt), calibrated with GRDC station data, were used to calculate the freshwater fluxes. On the basis of the latest WaterGAP 2.2d model, we could now derive the freshwater fluxes in a refined temporal resolution and for a considerably extended time period (1901-2016). We present a statistical analysis of monthly and annual freshwater input to the oceans within 5° and 10° latitude zones, from 5° cells along the coastlines and from the Global International Water Assessment regions (GIWA). Beyond that, the GRDC has revised its GIS product Major River Basins of the World, which is now consistent with the WMO Regions and Subregions. The freshwater fluxes have been determined likewise for these catchments. The provision of integrative data products is one of the objectives of the Global Terrestrial Network Hydrology (GTN-H) corresponding with the commitments of the WMO members at the eighteenth session of the World Meteorological Congress.