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SFU Thesis Template Files Understanding Extreme Precipitation Behaviour in British Columbia’s Lower Mainland Using Historical and Proxy Records by Christina Spry B.Sc. (Earth Sciences), St. Francis Xavier University, 2008 Research Project Submitted in Partial Fulfillment of the Requirements for the Degree of Master of Resource Management Report No: 527 in the School of Resource and Environmental Management Faculty of Environment Christina Spry 2013 SIMON FRASER UNIVERSITY Fall 2013 Approval Name: Christina Spry Degree: Master of Resource Management Report No.: 527 Title: Understanding extreme precipitation behaviour in British Columbia’s Lower Mainland using historical and proxy records Examining Committee: Chair: Thomas Rodengen PhD Candidate Karen Kohfeld Senior Supervisor Associate Professor Ken Lertzman Supervisor Professor Diana Allen Supervisor Department of Earth Sciences Date Defended/Approved: September 4, 2013 ii Partial Copyright Licence iii Abstract In British Columbia, Pineapple Express storms can lead to flooding, slope failures and negative impacts to water quality. Mitigating the impacts of extreme weather events in a changing climate requires an understanding of how local climate responds to regional-to- global climate forcing patterns. In this study, I use historical and proxy data to identify the distinguishing characteristics of Pineapple Express storms and to develop a tree ring oxygen isotope record (1960-1995) of local climate conditions in the Lower Mainland of British Columbia. I found that high magnitude Pineapple Express storms have significantly higher precipitation and streamflow than other storms types, which result in relatively high contributions of Pineapple Express storms to the annual water budget. As well, Pineapple Express precipitation is characterized by an enriched δ18O isotopic signature when compared to precipitation originating from the North Pacific Ocean. However, differences in source water do not appear to be driving the variability in tree ring δ18O ratios. Instead, tree ring isotopic values exhibit a regional climate pattern that is strongly driven by latitudinal temperature gradients and the Rayleigh distillation effect. Therefore, future warmer conditions may decrease the temperature gradient between the equator and the poles, which can be recorded in the tree ring isotope record. The results also suggest that warmer temperatures due to climate change could result in more active Pineapple Express storm seasons, with multiple PE storms happening over a short period of time. Concurrent storms significantly increase the risk to society because the resulting antecedent saturated soil conditions can trigger precipitation- induced natural hazards. Keywords: extreme weather; stable isotopes; Pineapple Express; British Columbia; climate change; tree rings iv Dedication To my parents, Jon and Laura, for their unconditional love and support. I couldn’t have done this without you. v Acknowledgements First, I would like to thank the members of my dedicated supervisory committee, Karen Kohfeld, Ken Lertzman, and Diana Allen for their continuous support and guidance. I respect and admire all of you greatly, so it was a pleasure to work with you closely and get to know you on a personal level. Thanks to David Dunkley and Metro Vancouver for the valuable input and allowing me access to the beautiful Capilano Watershed in North Vancouver. I would also like to acknowledge Henri Grissino-Mayer and Zheng-hua Li for their professional advice and mentoring. Numerous others contributed to this project by providing their data and sharing their expertise, so thanks to Michael Dettinger, Roderick Bale, Trevor Porter, Dinka Besic and Andy Cooper, and to my friends in the COPE lab, especially Celeste Barlow, Liz Sutton, and Joseph Bailey. This project was supported by a Simon Fraser University Community Trust Endowment Fund grant to Diana Allen, Ken Lertzman and Karen Kohfeld, as well as Karen Kohfeld’s NSERC Canada Research Chair program and NSERC Discovery Grant. vi Table of Contents Approval .......................................................................................................................... ii Partial Copyright Licence................................................................................................ iii Abstract .......................................................................................................................... iv Dedication ....................................................................................................................... v Acknowledgements ........................................................................................................ vi Table of Contents ...........................................................................................................vii List of Tables .................................................................................................................. ix List of Figures.................................................................................................................. x List of Acronyms .............................................................................................................xii Chapter 1. General Introduction ................................................................................. 1 1.1. References ............................................................................................................. 5 Chapter 2. Characterizing Pineapple Express Storms in British Columbia’s Lower Mainland Using Meteorological, Streamflow and Stable Isotope Data .............................................................................................. 7 2.1. Introduction............................................................................................................. 7 2.1.1. Study Area ................................................................................................ 12 2.2. Methods ............................................................................................................... 13 2.2.1. Meteorological and Streamflow Variables ................................................. 15 2.2.2. Characterizing PE from non-PE storms ..................................................... 15 2.2.3. Isotopic analysis of storm precipitation ...................................................... 16 2.2.4. Contribution of PE storms to annual precipitation and stream discharge .................................................................................................. 17 2.2.5. Temporal trends in PE frequency and annual storm maxima .................... 17 2.2.6. Relationships to climate oscillations .......................................................... 18 2.3. Results ................................................................................................................. 19 2.3.1. Characteristics of PE storms ..................................................................... 19 2.3.2. Meteorological and streamflow characteristics .......................................... 20 2.3.3. δ18O composition of storm precipitation ..................................................... 22 2.3.4. Contribution of PE storms to total annual precipitation and stream discharge .................................................................................................. 23 2.3.5. Frequency and annual storm maxima of PE storms .................................. 24 2.3.6. Correlation with climate oscillations ........................................................... 26 2.4. Discussion ............................................................................................................ 28 2.4.1. Distinguishing characteristics of PE storms ............................................... 28 2.4.2. Contribution of PE storms to total annual precipitation and stream discharge .................................................................................................. 29 2.4.3. Trends in PE storm behaviour ................................................................... 30 2.4.4. Relationships with climate oscillations ....................................................... 32 2.4.5. Relationship between PE storms, water resources and natural hazards in BC ........................................................................................... 33 2.4.6. Planning for future PE events .................................................................... 35 2.5. Conclusions .......................................................................................................... 37 vii 2.6. References ........................................................................................................... 40 2.7. Appendix. Meteorological and streamflow characteristics of all storm days at the Vancouver International Airport (1998-2007; N=112) and the Capilano Watershed (mid 2005-2007; N=94) ........................................................ 47 Chapter 3. Regional Climate Patterns Recorded in Tree Ring Isotopes in British Columbia ..................................................................................... 55 3.1. Introduction........................................................................................................... 55 3.2. Materials and methods ......................................................................................... 57 3.2.1. Study area ................................................................................................ 57 3.2.2. Tree ring sampling and dating
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