STATISTICAL ANALYSIS OF THE ATMSOPHERIC SULFATE HISTORY RECORDED IN GREENLAND ICE CORES DISSERTATION Presented in Partial Fulfillment of the Requirements for the Degree Doctor of Philosophy in the Graduate School of The Ohio State University By Lijia Wei, M.S. * * * * * The Ohio State University 2008 Dissertation Committee: Professor Ellen Mosley-Thompson, Advisor Professor Lonnie G. Thompson Approved by Assistant Professor Bryan G. Mark Assistant Professor Catherine A. Calder _________________________________ Advisor Atmospheric Sciences Graduate Program ABSTRACT The Greenland Ice Sheet contains exceptionally valuable chemical and physical histories that allow reconstruction of paleoclimatic and paleoenvironmental conditions, particularly for the Northern Hemisphere. The chemical analyses of five multi-century long ice cores from the PARCA and Summit collections have yielded a high resolution volcanic aerosol history, which complements volcanic histories extracted from other Greenland ice cores. A detailed ice-core volcanic index has been constructed and provides an improved estimate of the stratospheric sulfate burden which is an important input for models assessing the climatic impacts of volcanic eruptions. Additionally, these cores made it possible to confirm the timing of the arrival of the ash and aerosols from Laki over Greenland. This time-stratigraphic horizon is an essential dating tool for high northern latitude ice cores, including those from Greenland. The spatial characteristics of the sulfate aerosol deposition associated with specific eruptions provide information about the transport processes and the mechanisms dominating local deposition. Examination of the sulfate deposited from two eruptions, the 1783-84 A.D. Laki and the 1815 A.D. Tambora eruptions, reveals that precipitation ii over the southeastern coastal regions in 1783 may have been suppressed by a regional cooling associated with Laki. This also suggests that Laki aerosols were likely deposited primarily by dry deposition. In contrast, the sulfate deposition from Tambora is more spatially homogeneous, suggesting primarily stratospheric transport and deposition primarily via wet processes. To quantify the impact of geographical factors on the deposition of volcanic sulfate over Greenland, a category explanatory variable analysis was conducted. The results indicate that the location of ice cores relative to north/south or east/west side of ice divide strongly affects EXS deposition, but the elevation of the core site is relatively unimportant. Since 1850, the EXS flux extracted from Greenland ice cores has increased dramatically primarily as a result of anthropogenic sulfur emissions. To quantify this human impact as well as the effect of accumulation, a linear mixed model was applied. The results indicate that for every Gg increase in the annual NH sulfur emissions, there is a 0.0013% increase in the annual non-volcanic excess sulfate flux. The impact of accumulation on sulfate deposition varies over Greenland, likely as a function of the dominant local depositional mechanisms. The linear slopes of accumulation versus sulfate were found to group naturally by the regional accumulation. The differences among the slopes likely reflect the regional strength of the role of dry deposition. Additionally, local sources as well as the stochastic nature of depositional and post-depositional processes may also affect the sulfate flux deposition on the ice sheet. Thus, it will be valuable to reconstruct the histories of other chemical constituents that contribute to the sulfate flux, such as those from marine biota and biomass burning. Also, close examination of the depositional processes, such as continuous observations of the iii near surface and sulfate concentrations in fresh snow, may provide valuable information to improve our understanding of the relationship between the atmospheric sulfate background concentrations and the non-volcanic EXS flux deposited and preserved in the Greenland Ice Sheet. iv Dedicated to my parents Wei, Z. and Huang, B. v ACKNOWLEDGMENTS I wish to thank my advisor, Ellen Mosley-Thompson for the guidance, encouragement, and enthusiasm, which made this dissertation possible, and for her endless patience in correcting my linguistic errors. I am most grateful to Lonnie G. Thompson, Bryan G. Mark, and Kate A. Calder for their scientific guidance and for serving as my dissertation committee members. I am especially grateful to Mary Davis for her patience training me in the procedures for the dust analysis of ice core samples and her meticulous maintenance of the clean room that benefits the entire group. I would like to acknowledge Tracy Mashiotta for chemical analyses, Ping-Nan Lin for δ18O analyses, Paolo Gabrielli for trace element analyses, and Victor Zagorodnov who was in charge of drilling many of the ice cores used in this study. I want to thank Peter F. Craigmile and Kate A. Calder who guided my development of the statistical model. My colleagues and friends at the Byrd Polar Research Center and Geography Department, Natalie Kehrwald, Lei Yang and Meng-Pai Hung, provided me much appreciated inspiration. My close friends at OSU, Yuxiong Ji, Fanyu Zhou, Xi Zhang, Yi Zheng, and Yiqun Chen, made my four years in U.S. delightful. Finally, I would like to express my appreciation to the various sources of financial vi support I graciously received. The Ohio State University provided the University Fellowship that supported me the first year of study while a U.S. National Science Foundation award (NSF-OPP-0352527) supported three years of research and graduate education. My participation in the Crawford Point, Greenland drilling project was supported by the NSF Center for the Remote Sensing of Ice Sheets. The Dan David Prize Scholarship provided support in my final year of research and the Rick Toracinta Graduate Scholarship (OSU-BPRC) supported my presentation in 2008 at the Annual Meeting of Association of American Geographers vii VITA June 21, 1979………Born – Xiamen, China 2001………………..B.S. Geology, Nanjing University 2001-2003…………Graduate Research Associate, Polar Research Institute of China 2003………………..M.S. Geochemistry, Nanjing University 2008………………..M.A.S. Statistics, The Ohio State University 2005 - present………Graduate Research Associate, The Ohio State University PUBLICATIONS Research Publication 1. Wei, L., E. Mosley-Thompson, P. Gabrielli, L. G. Thompson, and C. Barbante, Synchronous deposition of volcanic ash and sulfate aerosols over Greenland in 1783 from the Laki eruption (Iceland), Geophysical Research Letters, 35, doi:10.1029/2008GL035117, 2008. 2. Zhou, L., Y. Li, J. Cole-Dai, D. Tan, B. Sun, J. Ren, L. Wei, and H. Wang, A 780 year record of explosive volcanic eruptions from the DT263 ice core from East Antarctica, (Chinese) Science Bulletin, 51 (18), 2189-2197, 2006. 3. Wei, L. Y. Li, D. Tan, L. Zhou, M. Yan, K. Hu, J. Wen, B. Sun, and L. Liu, Research on Micro-particle Implicating Pollutants in Polar Regions, Advances in Earth Science, 25, 216-222, 2005. 4. Wei, L. Y. Li, D. Tan, L. Zhou, M. Yan, K. Hu, J. Wen, B. Sun, and L. Liu, Review of Research on Insoluble Micro-particle in the Polar Cores, Chinese Journal of Polar Research, 15, 274-282, 2003. viii FIELDS OF STUDY Major Field: Atmospheric Sciences Minor Field: Statistics ix TABLE OF CONTENTS Page Abstract………………………………………………………………………………..ii Dedication……………………………………………………………………………..v Acknowledgements…………………………………………………………………vi Vita………………………………………………………………………………viii List of Tables………………………………………………………………………..xii List of Figures……………………………………………………………………….xiv Chapters: 1. Introduction…….………………………………..…………………………………1 2. Literature Review………………………………………..…………………………5 2.1 Greenland Ice Sheet overview………….……………………………………..5 2.2 Ice core paleoclimatology..………………….………………………...………8 2.3 General atmospheric circulation over Greenland……..………………………9 2.4 Annual snow accumulation…………….…………………….…………....…10 2.5 Surface temperatures…………………………….………………….………..15 2.6 Sulfate aerosols…………………………...………………….……..…….….17 2.7 Review of the various volcanic Indices……….…………………..…………21 2.7.1. Lamb’s Dust Veil Index (DVI)……………………………....……22 2.7.2. Mitchell Index………………..…..………...………………....……24 2.7.3. Volcanic Explosivity Index (VEI).……………………….……...…25 2.7.4. Sato Index…………………………..………………............…...….26 2.7.5. Ice Core Volcanic Index (IVI) ……………….………..……..…….28 3. Data and methodology………………………………………..…….…………….30 3.1 Description of the ice cores used in this study.………..……………..……....32 3.1.1 PARCA ice cores…………………………………….…………..….34 3.1.2 Non-PARCA cores………………..…………………………………36 3.2 Laboratory analyses and data processing………..…………………………...38 3.2.1 Laboratory analyses……………………….………….……………..39 3.2.2 Ice core dating……………..………………………………….…….40 3.2.3 Calculation of fluxes and excess concentration…………….………42 3.2.4 Extraction of volcanic information……………………………..…...43 3.2.5 Estimating missing data…………………….……………………….44 3.3 Primary ice core data sets………………….….……………………………..55 x 3.4 Additional data sets…………………………………..……..……...………...56 3.4.1 Ice core-derived secondary data sets…………..……………………56 3.4.2 Non ice core-derived secondary data sets employed………………56 4. Volcanic aerosol history…………………………………..…………...………….59 4.1 An ice core derived volcanic aerosol history ………………….……….……60 4.2 Temperature anomalies associated with volcanic eruptions….………….…..68 4.3 Potential problems with ice core-derived volcanic indices……………...…...71 4.4 Timing of the arrival of Laki ash and sulfate aerosols to the GIS………..….72 5. Spatial