| Summary: | Typescript Thesis (PhD)--University of Melbourne, School of Earth Sciences, 2005 Includes bibliographical references (leaves 151-168) Recent studies have demonstrated that the atmospheric concentrations of radiatively important greenhouse gases, including methane (CH4), carbon dioxide (CO2), nitrous oxide (N2O) and carbon monoxide (CO), have significantly increased during the past 200 years due to anthropogenic emissions. Analysis of air trapped in polar ice cores allows for past atmospheric variations due to natural climate conditions to be investigated, placing recent changes in a historical context. In this thesis new high- precision, multispecies measurements of atmospheric trace gas concentrations during the Holocene have been produced by analysing the air trapped in the ice at Law Dome, East Antarctica (66�46'08"E, 112�48�28�S). The ice core records are well-dated, have high age resolution and overlap with modem instrumental records due to the high accumulation rate at the drilling sites. The combination of high age resolution, precise dating and high precision measurements allows for subtle, decadal-scale variability to be detected. The multispecies measurement technique allows for biogeochemical causes of variations to be identified. The first part of this study focused on the late Holocene period (AD 0 to 1975). New high-precision records of CH4, CO2, N2O and CO have been produced for this period. The CH4 and CO2 measurements are used to build upon the existing Law Dome records of these gases during the last 1000 years, to validate and further define previously observed variations. The new measurements extend the records of these gases by another 1000 years. As a consequence of the multispecies measurement technique it has been possible to also measure N2O and CO during this period. These new measurements highlight the atmospheric response to the Little Ice Age (LIA) cooling (AD 1550 to 1800), particularly a 10 ppm decrease in atmospheric C02 between AD 1550 and 1600. A stabilization of CO2 during ...
|
|---|