Atmosphere beryllium‐7 concentrations over the Pacific Ocean

Abstract

Atmospheric 7Be is used as a tracer of stratospheric and upper tropospheric air, but most measurements of 7Be in surface air have been restricted to continental regions. We report here the extensive temporal and areal distribution of atmospheric aerosol 7Be concentration in the marine boundary layer. Measurements of 7Be have been carried out for the weekly filter samples collected at the Pacific island stations where are located between 30° N and 30° S in 1981 and 1985. High annual mean concentrations among the stations are observed at latitude between 20° and 30° in both hemispheres. There is little seasonal variation of 7Be at the nine stations. The lowest concentrations are found in the equatorial region due to relatively little subsidence of the air from the upper layer in this area and high precipitation within the ITCZ (intertropical convergence zone) resulting in rapid removal of the aerosol containing the 7Be. The significant correlation between the 7Be concentrations and the nitrate concentrations at the stations in the North Pacific supports the assumption that nitrate is transported from continental sources to the marine boundary layer through the free troposphere by the westerlies.