Nitrate records of a shallow ice core from East Antarctica: Atmospheric processes, preservation and climatic implications

Abstract

High-resolution records of nitrate (NO₃^-), oxygen isotope (δ ¹⁸O) and non-sea salt sulphate (nssSO₄^2- ) were studied using an ice core collected from central Dronning Maud Land in East Antarctica to identify the influence of environmental variability on accumulation of NO₃^- over the past 450 years. The results confirmed that multiple processes were responsible for the production and preservation of NO₃^- in Antarctic ice. Correlation between NO₃^- and nssSO₄^2- peaks revealed that sulphate aerosols released during major volcanic eruptions might have activated the production of nitric acid, which was scavenged by ion-induced nucleation in polar ice sheets. The correlation between the nitrate and δ¹⁸ O records further suggest that enhanced NO₃^- preservation in the ice occurred during periods of lower atmospheric temperature. Major shifts in the NO₃^- record of the ice core presently studied and its comparison with ¹⁰Be record from a core collected from South Pole suggest that a reduction in solar activity influenced the NO₃^- accumulation in Antarctica through enhanced production of odd nitrogen species.