Evidence of sea ice source in aerosol sulfate loading and size distribution in the Canadian High Arctic from isotopic analysis

Abstract

Abstract The influence of frost flowers and seawater brine on ion chemistry in snow, snowpack, ice cores, and aerosols is detected when a lower sulfate to sodium ratio than in seawater is present in polar regions. This evidence can be masked when large amounts of non‐sea‐salt sulfate are present from other sources such as biogenic and anthropogenic sulfate. Frost flower δ 34 S values were measured for the first time in frost flower sulfates and did not differ significantly from the sea salt δ 34 S values of +21‰. A method using stable isotopes is introduced to determine the limit of contributions from sea salt and sea ice sources (including frost flowers and brine) on sulfate concentrations in aerosol samples from Alert, Canada. Knowledge of the range of values of δ 34 S nss and the SO 4 /Na ratio found in sea ice sources (i.e., frost flowers) is used to quantitatively constrain the contributions from frost flowers and sea salt in the Arctic aerosol mass during the onset of winter in 2007 and 2008, allowing for quantification of non‐sea‐salt sulfate amounts during times when frost flowers are present. Frost flower and/or brine influence was found predominantly in the coarse‐mode aerosols (>0.95 µm). This method to determine the contributions from sea salt and sea ice sources can be carried over to future studies with snow and ice cores.