External radiation dose rate over the arctic ocean

摘要

Swedish Polar Research Secretariat arrenged a multidisciplinary scientific expedition to the Arctic Ocean in 2001 with the Swedish icebreaker Oden. The aim of the atmospheric research programme was to study the chemical, biological, physical and meteorological processes that control the formation of nanometre-size aerosol particles and their influence on climate change especially in the Arctic region. As a part of this programme external radiation was measured. The motivation was that ionising radiation has been suggested to be the reason for these particle formation events. The expedition started from Gothenburg, Sweden, on 26 June 2001 and ended at Svalbard on 29 August. The expedition sailed first to Svalbard area, then NE to the Lomonosov ridge, the Makarov basin and to the North Pole. Most of the atmospheric programme was conducted during the ice drift experiment at the 88th latitude, while the icebreaker was moored to an ice floe and drifted for three weeks in August 2001. Onboard the ship external radiation was measured with a pressurised ionisation chamber in 10 minute intervals. In the absence of gamma radiation coming from the Earth's crust the external radiation is practically due to the cosmic radiation. The absorbed dose rate varied between 0.040 and 0.045 (mu)Gy/h during the cruise. This corresponds to an ion production rate range of (7.3-8.3) X 10~(9) ion pairs per hour per kilogramme of air. These values are low compared to continental regions. A linear correlation between the absorbed dose rate (DR) and barometric pressure (P) was found: DR [(mu)Gy/h] velence 0.124 - P [hPa] X 8.1E-05. This inverse dependance is due to the more efficient attenuation of the cosmic radiation in the atmosphere as the total mass of an air column increases.