QUANTIFICATION AND CORRECTION OF “IN SITU” PRODUCTION OF N2O IN ICE CORES
Supervisors: H. Fischer (Univ. of Bern, CH), T. Roeckmann (Univ. of Utrecht, NL)
Academic secondments: CNRS-IGE (FR), Univ. of Utrecht (NL); Non-academic secondments: PAGES (CH)
Abstract: Ice cores represent the only direct paleo-atmospheric archive and allow – among others – the reconstruction of past greenhouse gas concentrations such as CO2, CH4 and N2O. However, previous analyses of N2O and its isotopes on ice cores have shown that N2O concentrations in Antarctic ice core sections from the last glacial, characterized by very high dust content, are subject to microbial in situ production of N2O from chemical nitrogen-bearing precursors in the ice. Thus, reliable information of glacial N2O concentrations is missing. Isotopic studies on N2O can potentially be used to separate the true atmospheric signal from the in situ produced N2O. The University of Bern has developed gas chromatography-mass spectrometry methods that allow to accurately measure both the nitrogen and oxygen isotopic signature of N2O in ice cores. In this DEEPICE PhD project this information will be used to identify the chemical nitrogen precursor compounds in the ice of various ice cores and to constrain potential microbial pathways of N2O production. The isotopic data will then be used to correct the glacial N2O record for the in situ contribution. New N2O isotopic analyses will be performed on ice from Antarctic ice cores for selected time periods over the last 800,000 years and used to quantify marine and terrestrial N2O source changes in the past.
Key words: ice cores, climate, nitrous oxide, greenhouse effect, gas chromatography – mass spectrometry
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