7th International Conference on Southern Hemisphere Meteorology and Oceanography


New estimates of continental discharge and oceanic freshwater transport

Kevin E. Trenberth, NCAR, Boulder, CO; and A. Dai

Annual and monthly mean values of continental freshwater discharge into the individual and global oceans at 1 degree resolution have been estimated using four runoff datasets. The most accurate estimate is based on stream-flow data from the world's largest 921 rivers, supplemented with estimates of discharge from unmonitored areas based on the ratios of drainage areas. Simulations using a river transport model (RTM) from the NCAR Community Climate System Model, forced by a runoff field, were used to derive the river mouth outflow from the farthest downstream gauge records. The new continental discharge estimate is then applied to estimate the meridional transport of freshwater within the oceans. The relatively new estimates of net water fluxes (E-P) over ocean surfaces derived from atmospheric moisture budget analyses based on the NCEP/NCAR and ECMWF reanalyses were used in the calculation of oceanic freshwater transport. Our results, which are improved in many aspects compared with previous estimates, show that global continental discharge is about 37288 km3/yr (1.2 Sv, 1 Sv=1x10^6 m3/s) or about 35% of terrestrial precipitation. We also show that latitudinal distributions of continental discharge have large impacts on the estimates of meridional oceanic freshwater transport. Results will be compared with direct ocean estimates with a focus on the Southern Hemisphere.

extended abstract  Extended Abstract (300K)

Session 11, The Southern Hemisphere oceans and air-sea interactions II
Wednesday, 26 March 2003, 10:30 AM-1:30 PM

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