Distribution of 7Be in surface air of Europe

Abstract

This study deals with long-term (span over three decades, 1972–2003) distribution of the cosmogenic isotope 7Be in surface air at 5 stations in Europe, extending from latitude 47°N to 68°N. The results suggest annual variability in all the data sets as well as a decrease in average 7Be activity with increasing latitude. Furthermore, a 9–10-year cyclical pattern is observed in the 7Be distribution, which is anticorrelated with the solar activity cycle. Our data also indicate a dynamic range of 7Be activity for each solar cycle and phase (maximum or minimum) which is higher at the middle compared to high-latitude regions. Additionally, about 10–20% relative deviation is observed in 7Be activity during solar maxima and minima compared to the total average 7Be. This feature indicates that some deviation in the worldwide 7Be activity data may relate to their acquisition, with respect to which part of a solar cycle they have been collected in (time span) and at which latitudinal spread. Estimate of 7Be flux onto European surface boundary layer vary from 0.4 to 0.9 × 1 0 10 atoms m - 2 yr - 1 which is strongly latitude dependent and our average value is comparable to the ∼ 0.7 – 0.8 × 1 0 10 atoms m - 2 yr - 1 across ocean and land.