Aerosol data from the EGRIP ice core covering the Last Glacial Maximum

Polar ice cores are archives of past climate conditions and atmospheric composition. Atmospheric aerosols deposited on the ice sheets and subsequently preserved in the ice provide detailed records of past atmospheric conditions. Analyses of these impurities therefore offer valuable insights into environmental changes in the past.

Here we present high-resolution impurity records from the East Greenland Ice Core Project (EGRIP) ice core measured with the University of Bern continuous flow analysis (CFA) set-up. Continuous melting and the analysis of only the inner part of the ice stick allows for high resolution while minimizing contamination. The analyzed components include water-insoluble dust particles as well as the dissolved impurities calcium, ammonium, and nitrate. For the dust record, we focus on the previously not studied changes in the main mode of the dust number concentration (<1 µm) and the dust refractive index. The dissolved species act as proxies for aridity (calcium) as well as vegetation cover and biomass burning (ammonium). Additionally, volcanic eruptions are imprinted in the electrolytic conductivity record of the meltwater.

The records span the period from 30k to 15k years BP, covering the Last Glacial Maximum (LGM). In Greenland ice cores, the LGM is characterized by high impurity content including dust, calcium, and nitrate. In contrast, ammonium concentrations are consistently low, reflecting extensive northern hemisphere ice sheets during this period. We observe dust concentrations up to 60 times higher than during the Holocene for particles in the 0.2-2 µm size range. Although dust concentrations remain high throughout the studied period, they exhibit pronounced variability. While the refractive index stays largely constant, the dust size distribution varies, but not in parallel with the concentration. Since the preserved size distribution is primarily controlled by atmospheric transport time, we hypothesize that dust source region contributions to Greenland changed during the LGM.