SO2 and SO4= in the arctic: interpretation of observations at three Norwegian arctic-subarctic stations

Three years of SO₂ and SO₄⁼ measurements (1978-81) at three Norwegian arctic-subarctic stations (70, 74, and 79°N) have been related to air mass trajectories. The average decrease in non-marine SO₄⁼-concentrations with increasing latitude was found to agree well with the latitude distribution of director short-path return-flow frequency of trajectories from the Eurasian source area. As expected from rts reactive, short-lived character, average SO₂-concentrations decreased much more rapidly than the frequency of source trajectories when moving into the arctic.

The seasonal variations in sulphur concentrations and source trajectories were less well correlated, best at the southernmost station. From the study of all individual pollution episodes (defined by ≥2 times average sulphur concentrations) we deduced that an increasing fraction of high sulphur levels could be explained by long-path return flow, when moving deeper into the arctic. On Spitsbergen 50% of all pollution episodes occurred during return-flow that had entered the arctic between Novaja Zemlya and the Taymyr peninsula.