Particle transport to the snow surface at the South Pole: the beginning of a tropospheric history

Abstract

Sodium concentration measurements in recent south polar snow by Legrand and Kirchener have been compared with surface aerosol measurements by Bodhaine, Shanahan and Samson et al., made at the South Pole Station. When a 180-day lag is applied, to allow spring/summer aerosols to be precipitated and incorporated into the autumn/winter snow layer, very good correspondence exists between mean aerosol concentration in air and mean sodium concentration in snow. This paper describes analyses of meteorological and glaciological processes to define glaciological and meteorological years, which justify the use of this 180 day lag. The accumulation rate of snow on the South Polar Plateau has been established through pit and core analysis during the occupation of the South Pole station, and through direct snow stake accumulation measurement. Precipitation has not been routinely measured, but is estimated through analysis of the station meteorological record and application of the cold air precipitation rates derived from the literature. The estimated precipitation is compared with measured accumulation to investigate lag between time of precipitation and accumulation, and to examine other possible sources of accumulated ice substance (riming, drifting, and direct sublimation) to define the glaciological year. Precipitation of sodium and other particles, through coagulation and other ice crystal attachment processes, is discussed relative to the meteorological year. The results of this work indicate that additional measurements relative to the gradients of temperature, wind, precipitation, and accumulation on the Polar Plateau are essential to the formal establishment of a theory relating glacio-chemical accumulation to meteorological processes, and formulating tropospheric history from glacial deposition.