The origin of massive ground ice in raised marine sediments along the Eureka Sound Lowlands, Nunavut, Canada A thesis submitted to McGill University in partial fulfillment of the requirements of the degree of Master of Science © Cameron Roy, August 2018 Department of Geography Acknowledgements This project was largely funded by the Natural Sciences and Engineering Research Council of Canada (NSERC), as part of Professor Wayne H. Pollard’s research program to investigate processes related to the formation and stability of permafrost and periglacial landforms in polar environments. Additional student support was supplied by a NSERC Canada Graduate Scholarship (Master’s) and by the Northern Scientific Training Program (NSTP). Logistical support in the field was provided by the Polar Continental Shelf Program (PCSP). This thesis was supervised by Prof. Pollard (Department of Geography, McGill University) and Prof. Denis Lacelle (Department of Geography, University of Ottawa). Thank you to Prof. Pollard for conceiving the project and organizing the field campaign. I appreciate the unparalleled guidance, knowledge and opportunities that I have gained as a direct result of your supervision. Thank you to Prof. Lacelle for outstanding supervision both in the field and in the laboratory. This work would not have been possible without your support. Thank you to Jean Bjornson at the University of Ottawa for indispensable direction and assistance in the laboratory. Thank you to Nimal de Silva and Smitarani Mohanty of the Geochemistry Laboratory at the Advanced Research Complex (Ottawa) for running the cation and anion samples on the ICP-AES. Thank you to Sarah Murseli and Christabel Jean at the A.E. Lalonde AMS Laboratory for running the radiocarbon samples. Thank you also to Mike Dalva and Paula Kesterman for laboratory and equipment support at McGill. Prof. Tim Moore (Department of Geography, McGill University) was the internal committee member for this thesis. Thank you for introducing me to the world of academic research and providing sage advice along the way. Thank you also to Melissa Ward Jones for ‘showing me the ropes’ – your mentorship in matters academic, bureaucratic and logistic has been much appreciated. Thank you to Fanny Amyot for comradeship and acting as my agent in Burnside. Special thanks to Beth Ann Clarke for providing me with accommodation during my extended visits to Ottawa. Finally, thank you to my parents, Doug and Diane, for unwavering support and encouragement. 2 Abstract/Resumé Massive ground ice is a feature of periglacial environments throughout Siberia, Alaska, northern Canada, Antarctica and Mars. The occurrence of massive ground ice raises questions about: i) its origin, ii) its extent across the landscape and iii) its response to climatic change. In the Canadian High Arctic Archipelago, tabular massive ground ice is found extensively throughout the Eureka Sound Lowlands (ESL) on Ellesmere and Axel Heiberg islands. Previous research by W.H. Pollard interpreted the ice as having a segregated origin related to deglaciation and Holocene marine regression. This study used a geochemical approach (stable water isotopes, major ions) to further explain the water source and freezing history of massive ground ice exposures in the ESL. Active layer sediments and permafrost cores from massive ice bodies were collected along an elevation gradient, from modern sea level to Holocene marine limit (~143 m a.s.l.). Results show that ESL ground ice formed during the Holocene in an open-system as raised marine sediments slowly froze from the ground surface downwards. Massive ice formed where the input rate of isotopically-depleted groundwater (from an underlying aquifer fed by the disintegration of the Innuitian Ice Sheet) was much greater than the downwards freezing rate. The extent of geochemical mixing and of the ice segregation process are reflections of the freezing rate – thus we can reconstruct permafrost aggradation along an elevation gradient of 143 m, which represents a span of ~8,000 years since deglaciation. La glace massive au sol est une caractéristique des environnements périglaciaires à travers Sibérie, Alaska, le nord du Canada, l’Antarctique et Mars. L’occurrence de la glace massive au sol produit des questions par rapport à : i) son origine, ii) son importance à travers le paysage et iii) sa réaction aux changements climatiques. Dans l’archipel de la haute arctique canadienne, on se trouve de la glace au tabulaire massive partout dans les basses terres des îles Ellesmere et Axel Heiberg. Des recherches précédentes par W.H. Pollard ont interprété la glace à avoir une origine intra-sédimentaire reliée à la déglaciation et régression marin pendant l’Holocène. Cette étude a utilisé une approche géochimique (isotopes stables d’eau, ions majeurs) pour expliquer la source d’eau et l’histoire de congélation des exposés de glace massive au sol dans les basses terres du Eureka Sound. Sédiments de la couche active et carottes de pergélisol ont été pris des masses de glace au sol à travers un gradient d’élévation – de le niveau de mer moderne jusqu’à la limite marine de l’Holocene (143 m a.s.l.). Nos résultats démontrent que la glace massive au sol de Eureka Sound est provenue d’un système ouvert durant l’Holocene, pendant que des sédiments marins élevés gelaient lentement de la surface vers le bas. La glace massive a formé quand la contribution de eaux souterraines appauvries en isotopes était beaucoup plus grand que la vitesse de congélation en direction vers le bas. L’ampleur du mixage géochimique et du processus de ségrégation de glace sont des résultats de la vitesse de congélation – donc on peut reconstruire la rapidité d’aggradation du pergélisol à travers un gradient de 143 m, ce qui représente un espace d’environ 8,000 ans après déglaciation. 3 TABLE OF CONTENTS 1. INTRODUCTION .................................................................................................................................... 8 1.1) AN UNUSUAL MINERAL......................................................................................................................... 8 1.2) TYPES OF GROUND ICE ........................................................................................................................ 10 1.3) MASSIVE GROUND ICE ........................................................................................................................ 13 1.3.1) Buried surface ice ....................................................................................................................... 14 1.3.2) Ice segregation in soils ............................................................................................................... 15 1.3.3) Wedge ice ................................................................................................................................... 19 2. STUDY AREA ........................................................................................................................................ 20 2.1) PHYSIOGRAPHY AND GENERAL SETTING ............................................................................................. 20 2.2) CLIMATE AND VEGETATION ................................................................................................................ 23 2.3) QUATERNARY HISTORY ...................................................................................................................... 23 2.4) PERMAFROST AND GROUND ICE .......................................................................................................... 26 3. RESEARCH OBJECTIVES .................................................................................................................. 29 4. METHODS .............................................................................................................................................. 30 4.1) INTRODUCTION ................................................................................................................................... 30 4.2) GEOCHEMICAL THEORY – AS APPLIED TO GEOCRYOLOGY .................................................................. 31 4.2.1) Stable water isotopes .................................................................................................................. 31 4.2.2) Major ion geochemistry .............................................................................................................. 34 4.2.3) Occluded gases ........................................................................................................................... 35 4.3) FIELD METHODS ................................................................................................................................. 36 4.3.1) Site selection ............................................................................................................................... 36 4.3.2) Field sampling ............................................................................................................................ 39 4.4) LABORATORY METHODS ..................................................................................................................... 41 4.4.1) Active layer (AL) samples ........................................................................................................... 41 4.4.2) Permafrost cores ........................................................................................................................ 41 4.4.3) Ice wedge (IW) samples .............................................................................................................