The hydroecological response of Greenlandic streams to a changing climate by Catherine Louise Docherty A thesis submitted to the University of Birmingham for the degree of DOCTOR OF PHILOSOPHY School of Geography, Earth and Environmental Sciences College of Life and Environmental Sciences University of Birmingham April, 2017 University of Birmingham Research Archive e-theses repository This unpublished thesis/dissertation is copyright of the author and/or third parties. The intellectual property rights of the author or third parties in respect of this work are as defined by The Copyright Designs and Patents Act 1988 or as modified by any successor legislation. Any use made of information contained in this thesis/dissertation must be in accordance with that legislation and must be properly acknowledged. Further distribution or reproduction in any format is prohibited without the permission of the copyright holder. Abstract Arctic streams are vulnerable to climate change due to the strong linkage between cryosphere, hydrology, physicochemical habitat and ecology. Our knowledge on how stream hydroecological dynamics will respond to climate change is largely based on the impact of the reduction in glacial extent in a warmer Arctic, however our knowledge of the response of Arctic streams with low glacial input are poorly understood. To address this knowledge gap, three field campaigns to Zackenberg (northeast Greenland) were carried out (2013 – 2015) to investigate snowmelt stream hydroecological patterns and processes. Streams were chosen that were sourced from both small and large snowpacks, representing low and high snowfall conditions. Streams with large snowpacks were found to have low channel stability and high suspended sediment concentration compared to streams with small snowpacks. Channel stability, rather than water temperature, was the most important factor influencing macroinvertebrate community dynamics, where streams with low channel stability had reduced macroinvertebrate density and taxa richness. The results of this research recommend new classifications to Arctic and alpine stream habitat types, and suggest that, as snowfall is predicted to increase in the Arctic, snowmelt-fed streams may experience decreased channel stability, and as such, a decline in macroinvertebrate density and diversity. ii iii Acknowledgements Firstly, I thank my supervisors Professor Sandy Milner and Professor David Hannah for their guidance, training and encouragement throughout the three and a half years, and Dr Tenna Riis (Aarhus University, Denmark) who provided valuable insights and support during fieldwork and the writing of this thesis. I am grateful to the UK Natural Environment Research Council (studentship: NE/L501712/1) and to the European Union Seventh Framework Programme (FP7/2007-2013) under grant agreement number 262693 (INTERACT) for their financial support. I am grateful to Richard Johnson for providing invaluable assistance in fieldwork preparation, to Chantal Jackson for producing the site maps, to Jamie Peart for his continuous willingness to help in office- based problems, to Gillian Kingston and Eimear Orgill for their support with water chemistry analysis, and to Helen Jones and Eileen Jackson for arranging supervisory meetings. I thank Andy Moss for his training in chironomid identification and Steve Brooks (Natural History Museum, London) for verifying chironomid specimen identifications. I am grateful to Steve Dugdale for his assistance with R coding problems, and Phil Blaen for his advice on nutrient uptake experiments and all things polar hydrology. I owe a special thank you to everyone who helped the fieldwork run smoothly over the three field campaigns. Zackenberg logistics for their support and for providing tools and an endless supply of metal poles, and to the Biobasis and Geobasis team members for providing insights into the research area. To Lars Holst Hansen, for helping retrieve data loggers, allowing us to collect more data than we could have in the short field campaigns, and Jannik Hansen, for always being helpful and happy, even in the most Arctic of weather conditions. I am grateful to Simon Rosenhøj Leth for his assistance and company during two field campaigns, and I owe a big thank you to Dina Laursen Kalogirou, if it wasn’t for her constant supply of homemade cake to keep us going in the cold, none of this would have been possible. I am grateful to the Greenland Ecosystem Monitoring Programme for the use of meteorological data, that were provided by the Department of Bioscience, Aarhus University, Denmark in collaboration with the Department of Geosciences and Natural Resource Management, Copenhagen University, and Asiaq – Greenland Survey, Nuuk, Greenland. I thank Leonie Clitherow, Tom Aspin, Zining Wang, Jess Picken, Suffeiya Supian and Eva Loza Vega for their friendship, advice, cake and guacamole over the last three and a half years, as well as the many other people in room 425 and GEES. Finally, I am most gratefully to Miquel Vall-llosera for his support, guidance and his help with my many R- related crises, and to my family for supporting me unconditionally throughout. iv Contents CHAPTER 1: INTRODUCTION ........................................................................................1 1.1. Climate change and stream systems in the Arctic ........................................................2 1.2 Research gaps .................................................................................................................3 1.3 Aim and objectives ..........................................................................................................5 1.4 Research design ..............................................................................................................6 1.5 Zackenberg .....................................................................................................................9 1.6 Previous research at Zackenberg ................................................................................. 16 1.7 Thesis structure ............................................................................................................ 17 1.8 References ..................................................................................................................... 18 CHAPTER 2: CONTROLS ON STREAM HYDROCHEMISTRY DYNAMICS IN A HIGH ARCTIC SNOW-COVERED WATERSHED ....................................................... 25 2.1 Introduction .................................................................................................................. 27 2.2 Methods ......................................................................................................................... 29 2.2.1 Study site .............................................................................................................. 29 2.2.2 Sampling framework............................................................................................. 33 2.2.3 Sample analysis .................................................................................................... 34 2.2.4 Data analysis......................................................................................................... 35 2.3 Results ........................................................................................................................... 35 2.3.1 Hydroclimatological variables during the three field campaigns ............................ 35 2.3.2 Snowpack size and stream channel stability .......................................................... 37 2.3.3 Spatial variation in stream hydrochemistry dynamics ............................................ 41 v 2.3.4 Interannual variation in stream hydrochemistry dynamics ..................................... 53 2.4 Discussion ...................................................................................................................... 56 2.4.1 Stream channel stability and suspended sediment characterisation ........................ 56 2.4.2 Spatial variation in channel stability and stream hydrochemistry dynamics ........... 58 2.4.3 Interannual variation in stream hydrochemistry dynamics ..................................... 60 2.4.4 Water sources and their impact on stream hydrochemistry .................................... 60 2.4.5 Regional implications of climate change and conclusions ..................................... 61 2.5 References ..................................................................................................................... 63 CHAPTER 3: LARGE THERMO-EROSIONAL TUNNEL FOR A RIVER IN NORTHEAST GREENLAND ........................................................................................... 71 3.1 Introduction .................................................................................................................. 73 3.2 Methods and Data ......................................................................................................... 74 3.2.1 Site description ..................................................................................................... 74 3.3 Observation and description of thermo-erosional niche ............................................. 75 3.4 Discussion and conclusions ........................................................................................... 80 3.4.1 Potential implications and processes in a changing climate ................................... 80 3.5 References ....................................................................................................................