Master Thesis Defense by Annika Stratidaki

Title: High-Precision δ13C − CH4 Characterization of  Methane in Air Samples from Reference Gas Bottles and Ice Core Samples

Abstract:
Methane (CH4) accounts for approximately one - fifth of the rise in radiative forcing attributed to anthropogenic greenhouse gases. Since the industrialization, rapidly growing human activities, particularly in the areas of agriculture, fossil fuel use, and waste disposal, have significantly increase methane emissions. Atmospheric methane concentrations have doubled in response to the emissions growth, and continue to rise. These increasing concentrations have raised concern due to their potential effects on atmospheric chemistry and climate. This study focuses on isotopic analysis of methane, particularly δ13C − CH4, to shed light on its sources and sinks and their responsiveness to environmental changes.
The isotopic composition, notably the ratio of 13C/12C, serves as a tracer to distinguish between different methane sources and offers insight into sink processes. Air samples from ice cores drilled in polar ice sheets contain trapped ancient methane, enabling the reconstruction of past isotopic signatures and providing the insights into how methane emissions have historically influenced and responded to climate shifts. Here, we employed a specialized analytical setup, including separation traps to isolate CH4 from the main components of the atmosphere and a GC/C/GC/IRMS (gas chromatograph/combustion/gas chromatograph/isotope ratio mass spectrometer) optimized for δ13C−CH4 measurements.
In this study, a newly-built sublimation setup was tested for the extraction of air from an ice core sample for the first time. Key objectives include improving isotope ratio analysis techniques, δ13C isotopic characterization of reference bottles and validating the sublimation system’s performance in isolating methane for precise measurements.

Supervisor: Thomas Blunier
Censor: Peter Langen