Master thesis defense by Janani Venkatesh

Title: An improved Gas-CFA system for methane measurements and preliminary results from the Dye-3 ice core

Abstract: Gases in ice cores are one of the most pristine records of the Earth’s atmosphere in the past. They present the unique opportunity for studying the concentration of greenhouse gases during various earlier climatic conditions, thereby enabling us to better predict what the future holds in the context of climate change. The development of laser spectroscopy and Continuous Flow Analysis (CFA) techniques has introduced the possibility of high resolution gas measurements in ice cores. The current work focuses on improving established techniques by addressing some of the uncertainties observed in previous works. A hydrophobic membrane module has been used to replace the debubbler as the main extraction unit. The extracted and dehumidified gas is then measured by a Wavelength-Scanned Cavity Ringdown Spectrometer (WS-CRDS) to quantify methane mixing ratios in the sample stream. The various parameters impacting the system are characterized, and consequent corrections to the data accounted for. Further possible improvements based on this work are also discussed. This method has been implemented in the CFA measurements of the Dye-3 ice core and preliminary results from the campaign are presented here.