A TRITIUM BUDGET FOR THE NORTH-ATLANTIC

We develop a new model bomb-H-3 budget for the North Atlantic between 1950 and 1986, The model, which calculates the atmospheric and contine ntal H-3 delivery as well as the advective H-3 transports from the Sou th Atlantic and Arctic, agrees within about 10% with the H-3 inventori es computed from the 1972 GEOSECS and the 1981-1983 Transient Tracers in the Ocean (TTO) observations. The decay-corrected H-3 inventory for the North Atlantic increased by about 43% between the GEOSECS and TTO programs (1972 to 1981), and the inflow of high H-3 polar water from the Arctic into the North Atlantic is found to be crucial for correctl y simulating this increase. Key aspects of the model that differ from previous studies include the treatment of vapor/rain isotopic equilibr ium, the continental vapor flux, and the downward flux of water vapor into the ocean. The sensitivity of the atmospheric H-3 delivery to mod el parameters and to seasonal and interannual variability are explored .