Continuous 25-yr aerosol records at coastal Antarctica – I: inter-annual variability of ionic compounds and links to climate indices

Rolf Weller,Dietmar Wagenbach,Michel Legrand,Christoph Elsässer,Xiangshan Tian-Kunze,Gert König-Langlo

doi:10.1111/j.1600-0889.2011.00542.x

Abstract

The aerosol climatology at the coastal Antarctic Neumayer Station (NM) was investigated based on continuous, 25-yr long observations of biogenic sulphur components (methanesulfonate and non–sea salt sulphate), sea salt and nitrate. Although significant long-term trends could only be detected for nitrate (−3.6 ± 2.5% per year between 1983 and 1993 and +4.0 ± 3.2% per year from 1993–2007), non-harmonic periodicities between 2 and 5 yr were typical for all species. Dedicated time series analyses revealed that relations to sea ice extent and various circulation indices are weak at best or not significant. In particular, no consistent link between sea ice extent and sea salt loadings was evident suggesting only a rather local relevance of the NM sea salt record. Nevertheless, a higher Southern Annular Mode index tended to entail a lower biogenic sulphur signal. In examining the spatial uniformity of the NM findings we contrasted them to respective 17 yr records from the coastal Dumont d’Urville Station. We found similar long-term trends for nitrate, indicating an Antarctic-wide but not identifiable atmospheric signal, although any significant impact of solar activity or pollution could be ruled out. No inter-site variability on the multiannual scale was evident for the other ionic compounds.

Highlights

In addition to stable water isotopes recorded in Antarctic ice cores, important paleo-climate information comes from ionic impurities and insoluble dust preserved in this archive
In addition respecting figures of the Dumont d’Urville Station (DDU) time series, the meteorological data from Neumayer Station (NM) as well as sea ice extent (SIE), Southern Annular Mode (SAM) and Southern Ocean Index (SOI) are shown in the Supporting Information Appendix S2
Concluding Remarks Spanning more than 25 years, the continuous atmospheric observation of ionic aerosol species at the coastal Antarctic Neumayer Station constitutes the longest of such records within the Antarctic realm. In view of this extended observational period we attempted to establish a coastal Antarctic aerosol climatology focussing on the long term and inter-annual variability of major ion components comprising biogenic sulfur (MS and nss-SO42-), sea salt, and nitrate

Summary

Introduction

In addition to stable water isotopes recorded in Antarctic ice cores, important paleo-climate information comes from ionic impurities and insoluble dust preserved in this archive. In this context a review of the ionic ice composition originating from deposition of aerosol and water-soluble trace gases is given by Legrand and Mayewski, (1997). Mayewski et al (2009) highlighted in a comprehensive review the pivotal role of chemical proxies in reconstructing the history of the Southern Ocean and Antarctic climate over the last few millennia In this context, the most meaningful ionic impurities have proved to be the marine biogenic methanesulfonate (MS), non sea salt sulfate (nss-SO42-) that is mainly biogenic or sporadically of volcanic origin, and Na+, a genuine sea salt tracer. Unlike anthropogenic impact, which seems only evident in nitrate records from Greenland ice cores (Legrand and Mayewski, 1997; Fischer et al., 1998), nitrate deposition onto the Antarctic ice sheet has been attributed to various sources including stratospheric N2O oxidation and low latitude lightning activity (Legrand and Kirchner, 1990; Wolff, 1995), polar stratospheric cloud (PSC) precipitation (Mayewski and Legrand, 1990) and solar activity (e.g. McCracken et al, 2001; Palmer et al, 2001)

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