PhD defence by Peter Sperlich – Niels Bohr Institute - University of Copenhagen

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PhD defence by Peter Sperlich

δ13C-CH4 in ice core samples: Analyses, referencing and data interpretation approaches

Ice core records of δ13C-CH4 reflect the variability of CH4 biogeochemistry in response to climate change and show this system is far more complex than expected. The first part of this work is concerned with the development of analytical techniques that allow 1) precise referencing and 2) measurements of δ13C-CH4 in ice core samples as is required when δ13C-CH4 records that are measured in several laboratories are merged for analysis. Both the referencing and measurement techniques have been compared to further laboratories which proofed the accuracy of the analytical systems. The second part of this work is focussed on the analysis δ13C-CH4 on two time scales that include the very rapid precursor event of Dansgaard-Oeschger (DO) event 21 as well as the variability over the last glacial-interglacial cycles. While δ13C-CH4 suggests the rapid variability in CH4 mixing ratios during DO-21 is likely caused by increased tropical wetland CH4 sources, the δ13C-CH4 variability on glacial-interglacial time scales correlates well with a range of parameters that are likely to impact atmospheric δ13C-CH4 through variations in microbial CH4 formation pathways, vegetation composition and the ratio of biogenic versus pyrogenic CH4 emissions.

Thomas Blunier, Prof. at Centre for Ice and Climate, NBI

Assessment committee
Anders Svensson, Ass. prof. at Centre for Ice and Climate, NBI
Ed Brook, Prof. at Department for Geosciences, Oregon State University, USA
Martin Heimann, Director, Prof. at Max Planck Institute for Biogeochemistry, Jena, Germany

 If interested please contact Peter Sperlich for a copy of the thesis sperlich