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Representativeness and seasonality of major ion records derived from NEEM firn cores

Type of publication Peer-reviewed
Publikationsform Original article (peer-reviewed)
Publication date 2014
Author Gfeller G., Fischer H., Bigler M., Schüpbach S., Leuenberger D., Mini O.,
Project Schweizerische Beteiligung an der Eis-Tiefbohrung in Nordwest Grönland NEEM (Teil 2)
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Original article (peer-reviewed)

Journal The Cryosphere
Volume (Issue) 8
Page(s) 1855 - 1870
Title of proceedings The Cryosphere
DOI 10.5194/tc-8-1855-2014

Open Access

URL http://www.the-cryosphere.net/8/1855/2014/
Type of Open Access Publisher (Gold Open Access)

Abstract

The seasonal and annual representativeness of ionic aerosol proxies (among others, calcium, sodium, ammonium and nitrate) in various firn cores in the vicinity of the NEEM drill site in northwest Greenland have been assessed. Seasonal representativeness is very high as one core explains more than 60% of the variability within the area. The inter-annual representativeness, however, can be substantially lower (depending on the species) making replicate coring indispensable to derive the atmospheric variability of aerosol species. A single core at the NEEM site records only 30% of the inter-annual atmospheric variability in some species, while five replicate cores are already needed to cover approximately 70% of the inter-annual atmospheric variability in all species. The spatial representativeness is very high within 60 cm, rapidly decorrelates within 10m but does not diminish further within 3 km. We attribute this to wind reworking of the snow pack leading to sastrugi formation. Due to the high resolution and seasonal representativeness of the records we can derive accurate seasonalities of the measured species for modern (AD 1990–2010) times as well as for pre-industrial (AD 1623–1750) times. Sodium and calcium show similar seasonality (peaking in February and March respectively) for modern and pre-industrial times, whereas ammonium and nitrate are influenced by anthropogenic activities. Nitrate and ammonium both peak in May during modern times, whereas during pre-industrial times ammonium peaked during July–August and nitrate during June–July.
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