Trace gases in Antarctic and Greenland firn and ice: a record of carbonyl sulphide and the isotopologues of chlorofluorocarbons
Year: 2015
Type: dissertation
Abstract: Through the industrial revolution of the last 250 years, trace gases have had a significant impact on the climate.Of particular relevance to this work are species which facilitate the destruction of stratospheric ozone.In this thesis, I focus on four of these species.Understanding the release, reaction and transport pathways of the man-made chlorofluorocarbons (CFCs) could help us to mitigate their destructive effect.Previous studies have found that both source and sink processes significantly alter the isotopic composition of trace gases (e.g.N 2 O and CFC-12).Measuring these changes can be used to better constrain the interaction of these gases with the atmosphere.Atmospheric histories of δ( 37 Cl) and δ( 13 C) in CFC-11, CFC-12 and CFC-113 are presented, covering the last 20 -60 years.Air samples came from Greenland (NEEM) and Antarctic (Fletcher Promontory) polar firn, with additional samples taken from an archive of Southern Hemispheric background air (Cape Grim, Tasmania).This study extends the novel approach to measuring trace gas isotope ratios in small air volumes (200 -600 ml), using a single-collector gas chromatography-mass spectrometry system.Carbonyl sulphide (COS) is the principal source of sulphur in the stratosphere, where it breaks down into sulphate aerosol which catalyses the destruction of ozone.Air was extracted from Greenland (NEEM) and Antarctic (DE08, DML (BAS) and DSS) ice core samples and analysed for COS and a range of other trace gas mole fractions.The COS measurements were affected by a previously unknown post-extraction growth effect, leading to higher than expected values.This study also presents new COS measurements in firn air from NEEM and the Southern Hemisphere (EDML, Antarctica).The observed increase and subsequent decrease largely reflects changes in anthropogenic emissions during the 20 th century.These measurements also indicate that regional and site-specific effects have a significant influence on the recorded atmospheric history of COS.
Author: Samuel Allin
Language: English
Subfield: Atmospheric Science
Field: Earth and Planetary Sciences
Domain: Physical Sciences
SDG: Climate action
Open Access status: green
OpenAlex ID: W2278270285