Continental outflow

Inomata Y. Iwasaka Y. Osada K. Hayashi M. Mori I. Kido M. Hara K. and Sakai T. (2006). Vertical distributions of particles and sulphur gases (volatile sulfur compounds and S02) over East Asia Comparison with two aircraft-borne measurements under the Asian continental outflow in spring and winter. Atmospheric Environment, 40(3), 430-444. 

The bulk mantle has a constant volume (a free parameter depends on D" and RDM volumes). The starting U concentration is that of the bulk silicate Earth and that of He is calculated for a closed system with a Loihi He/ He ratio. The main He outflow is to the atmosphere by degassing a constant volume with time (i.e., first order degassing). U is largely transferred to the continental crust at a set first-order removal rate. Smaller fluxes of He and U to D" and RDM (via the altered ocean crust and depleted oceanic lithosphere, respectively) also occur. Small inputs occur from subduction of continental crust and from D" and RDM. Present isotopic compositions are those seen in MORE. 

The model continental crust grows linearly over 4.5 Ga to the present volume. It only serves to deplete the bulk mantle of U. Return to the bulk mantle by subduction occurs at a rate set by those of continental growth and mantle outflow. 

Another pathway whereby tritium enters the ocean is through continental runoff and river flow. Tritium deposited to the continents ultimately flows to the oceans via lakes, rivers and groundwater flow, but is retained within the continental hydrosphere for time-scales of many years, thereby introducing a delayed input to the oceans. Further, when computing the time-evolving tritium inventory within an ocean basin, it is necessary to consider inflow and outflow across the basin s boundaries. 

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