The role of atmospheric circulation patterns on the variability of ice core constituents in coastal Dronning Maud Land, Antarctica

Abstract

Atmospheric circulation pattern highly influence the concentrations of ice core constituents by affecting their source strength, transport path and deposition. In 2007 four firn cores were drilled in the Ekströmisen catchment area (ECA), covering a time interval of 50 years. The ECA is located in the hinterland of the German wintering station Neumayer that is characterized by very high accumulation rates. The objective of this study is to connect records of ice core constituents with atmospheric circulation pattern on regional and synoptic scale. Continuous flow analysis (CFA) was used to quantify concentrations of firn core constituents and discrete samples were taken that were analyzed using ion chromatography (IC). Spatial gradients of mineral dust, sea salt, sulphate and nitrate showed that sea salt concentrations are closely connected to the cyclones approaching from the southern ocean. Mineral dust particles have their source in Patagonia and are then transported in the upper troposphere to the Antarctic plateau, where they subside. From the Antarctic plateau they are transported to the ECA by katabatic winds. Sea salt particles are closely connected to local atmospheric processes as cyclone activity. Sulphate in coastal Antarctica depends on the presence of sea ice and the solar cycle. Nitrate concentrations are uniformly distributed within the ECA, indicating that nitrate concentrations are independent of local conditions. To investigate the atmospheric circulation pattern connected to events in firn core constituents monthly NCEP-NCAR reanalysis data where used to calculate composite maps. The results showed that on the southern hemispheric scale, concentrations of mineral dust and sea salt mainly depend on the conditions in the source region and that a strong source supports high concentrations of mineral dust and sea salt. In conclusion, the knowledge of the prevailing local changes in wind and the accompanying changes in concentrations of firn core constituents can be used to investigate changes in local winds and topography in a region were atmospheric measurements are sparse. On the southern hemispheric scale, concentration of firn core constituents can help to better understand the climate in the source region. The method presented in this study provides a robust analysis method for ice core records that gives the opportunity to compare ice core data with atmospheric models.