High winter concentrations of SO₂ in the Norwegian Arctic and transport from Eurasia

Abstract

Since July 1977, the Norwegian Institute for Air Research has been studying trace gases and aerosols in the atmosphere at Bear Island, an Arctic site located at 74° N and 19° E. Although Bear Island lies well north of the Arctic Circle, the warm Norwegian Sea gives it an annual mean temperature of −1.8 °C, considerably warmer than at many other Arctic locations (Barrow, Alaska, for example, is 350 km farther south but has an annual mean of −12.2 °C). In summer, Bear Island is surrounded by open water; in winter there is open sea to the south and west and pack ice to the north and east. Atmospheric samples are taken 20 m above mean sea level and 2 m above local ground: high-volume filters are taken three times a week and analysed for various elements by atomic absorption, neutron activation and wet chemistry; sulphate and sulphur dioxide are measured daily by a method similar to that of Johnson and Atkins¹, using low-volume (16 m³) prefilters for sulphate and KOH-impreg-nated afterfilters for SO₂. The collection efficiency of this method for SO₂ has been tested extensively². Results for the high-volume samples have been reported³; here we discuss the SO₂ data, which seem to indicate that during winter there is efficient transport from Eurasian midlatitudes, due at least in part to long atmospheric residence times in and around the Arctic.