Water balance modelling of (Sub-)Arctic rivers and freshwater supply to the Barents Sea Basin

Recently, changes in the freshwater supply by rivers to the Arctic Ocean have attracted a great deal of attention. However, quantitative assessments of changes in the annual and seasonal discharge regime of (Sub-)Arctic rivers resulting from climate change are still far from accurate. The sensitivity of discharge to potential changes in climate in two river catchments of intermediate size (10⁴-10⁵ km²), the Tana River in northern Fennoscandia and the Usa River in northern Russia, both draining into the Barents Sea Basin, was evaluated using a spatially distributed water balance model. The tentative results show that discharge amounts during peak flow might remain more or less the same or show a slight increase. However, peakflow events are expected to occur about 20 days or more earlier in spring. Concerning annual discharge amounts a strong increase of 25% for the Usa River and even 39% for the Tana River is simulated in conformity with projected increases in precipitation. Obviously, the resulting increases of the annual freshwater influx from the Tana River (from 5.3 to 7.3 km³) and that of the Usa River (from 42 to 52 km³) into the Barents Sea are insignificant in absolute terms. But in relative terms they agree remarkably well with earlier estimates of changes in freshwater inflow by the very large (Sub-) Arctic rivers.