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Seasonal and Interannual Variability of Oceanographic Conditions in a Northeast Greenland Fjord By Seasonal and interannual variability of oceanographic conditions in a Northeast Greenland Fjord by Wieter Boone A thesis submitted to the Faculty of Graduate Studies of The University of Manitoba in partial fulfilment of the degree of Doctor of Philosophy Department of Environment and Geography University of Manitoba Winnipeg, MB, Canada Copyright © 2018 by Wieter Boone i Abstract The Arctic is undergoing rapid changes due to climatic changes. Studies show that the Arctic is not only warming, but also freshening, which can induce changes to the distribution and spreading pathways of freshwater and impact ecosystems. Here, we focus on the coast of Northeast Greenland, which lies along the primary outflow shelf of the Arctic Ocean. Long term mooring-arrays monitor the gateways of the East Greenland Current at Fram Strait and Denmark Strait, but seasonal and interannual variability of oceanographic conditions along the coast of Northeast Greenland and its impact on fjord hydrography are not well known. This is mainly due to costs and logistical constraints encountered when operating in such a harsh and remote environment, where sea ice hampers coastal navigation. For this thesis, we analyzed in-situ observations, including moorings, from Young Sound-Tyrolerfjord (74° N), to gain more knowledge on the seasonal and long-term response of the fjord system to local and regional processes inducing changes in oceanographic conditions in the fjord and in the coastal domain. Our results include a description of the variability in hydrography and circulation during the ice- covered period, an impact analysis of coastal freshening on the renewal of the fjord basin water, and a process study of the drivers of freshwater variability along the coast of Northeast Greenland. The results suggest that sea ice melt along the coast is a prominent driver of freshwater variability in the coastal domain, and that sea ice melt might be impacted by the recirculation of warm Atlantic Water. An increase of temperatures in the North Atlantic could induce more sea ice might melt at higher latitude and freshen the coastal waters of Northeast Greenland. This is important, as our data already shows that ii after strong costal freshening in the periods since 2005, fjord bottom renewal of Young Sound-Tyrolerfjord was prevented, which may affect the fjords ecosystem functions. This study was enabled by the extensive dataset from the Marin Basis Monitoring Program under the Greenland Ecosystem Monitoring Program, and underlines the importance to maintain strong monitoring capacity in Northeast Greenland, to asses recent and future changes to the marine system due to climate change. iii Acknowledgements A sincere thanks to my supervisors Dr. Søren Rysgaard and Dr. Igor Dmitrenko for their leadership and enthousiasm. I extend my thanks to my committee members Drs. Zou Zou Kuzyk, Jens Ehn, Jørgen Bentsen and Dirk Notz, and CEOS Director Tim Papakyriakou for their support and guidance during this research project. Furthermore, I would like to thank all colleagues at CEOS and within the Arctic Science Partnership for their part in this research project. Financial support for this research was provided by the Canada Excellence Research Chair (CERC) unit at the University of Manitoba’s Centre for Earth Observation and Science (CEOS), the Canada Research Chair (CRC) program, the Canada Foundation of Innovation (CFI), the Natural Sciences and Engineering Research Council of Canada, Research Manitoba, and the University of Manitoba, Aarhus University and the Greenland Institute of Natural Resources. I have personally received support via the University of Manitoba’s International Graduate Student Scholarship and the University of Manitoba Graduate Scholarship. This research contributes to the research programs of the Arctic Science Partnership (ASP), the Canada Excellence Research Chair of Dr. Søren Rysgaard and ArcticNet. iv The possibility to do research in the Arctic with challenging fieldwork was the incentive of my move to Canada. A great journey, which I tried to live to the fullest together with my wife Isabeau. It was a success. Big thanks to Odile, Masayo, Sergey, Lorenz, Leendert, John, Annie, Tim, Jens, Heather, Yubin, Michelle, Satwant, Nathalie, Søren, Igor, Denise, David, Lucette and Linda for their part in this undertaking. Thanks to my mom, dad, sisters and friends for the support and love we received via dozens of postcards and visits. Thanks to Lio, just for being there. Memories from the expedition to Young Sound-Tyrolerfjord in 2013 : coastal Northeast Greenland as seen from Twinotter-plane, myself casting a CTD on sea ice, my supervisors (Igor and Søren) casting a CTD, Ice mass balance buoy on the foreground with researchers casting a CTD in the background (photo credit: Wieter Boone and Sergei Kirillov) v Contents Abstract .............................................................................................................................. i Acknowledgements .......................................................................................................... iii Contents ............................................................................................................................. v List of Tables ..................................................................................................................... ix List of Figures ..................................................................................................................... x Use of Copyrighted Material .......................................................................................... xvii Chapter 1 Introduction .................................................................................................... 1 1.1 Motivation ............................................................................................................. 1 1.2 Thesis Objectives ................................................................................................... 3 1.3 Thesis Outline ........................................................................................................ 3 Chapter 2 Background ..................................................................................................... 7 2.1 Hydrography of the Arctic Marine System ............................................................ 7 2.1.1 Regions, domains and general circulations ................................................ 7 2.1.2 Primary freshwater sources of the Arctic Ocean ..................................... 10 2.1.3 Fate of freshwater in the Arctic Ocean .................................................... 12 2.2 Hydrography of the Greenland Sea ..................................................................... 14 2.2.1 General circulation and water mass transformation in the Nordic Seas . 14 2.2.2 East Greenland Current ............................................................................ 17 2.3 Summary .............................................................................................................. 25 References ...................................................................................................................... 26 Chapter 3 ............................................................................................................................ 33 vi Circulation and fjord-shelf exchange during the ice-covered period in Young Sound- Tyrolerfjord, Northeast Greenland (74°N) ...................................................................... 33 3.1 Introduction .............................................................................................................. 34 3.2 Physical setting .................................................................................................... 37 3.2.1 Young Sound-Tyrolerfjord system .................................................................. 37 3.2.2 Coastal water masses ............................................................................... 38 3.2.3 Sea ice cover in winter 2013-2014 ................................................................. 39 3.3 Data and methods ............................................................................................... 40 3.3.1 Ice-tethered mooring data ....................................................................... 40 3.3.2 Hydrographic and meteorological data .................................................... 43 3.4 Results .................................................................................................................. 44 3.4.1 Seasonal thermohaline variability ............................................................ 44 3.4.2 Seasonal circulation .................................................................................. 45 3.4.3 Tidal analysis ............................................................................................. 50 3.4.4 Cross sill exchange .................................................................................... 53 3.5 Discussion ............................................................................................................ 57 3.5.1 Circulation dynamics and environmental factors .................................... 57 3.5.2 Temporal changes in fjord circulation pattern ......................................... 59 3.5.3 Link between sea ice cover and circulation.............................................. 60 3.5.4 Cross-sill salt fluxes ..................................................................................
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