Manuel Helbig¹, James Michael Waddington², Pavel Alekseychik^3,4, Brian D Amiro⁵, Mika Aurela⁶, Alan Barr⁷, Thomas A Black⁸, Peter Blanken⁹, Sean Kevin Carey¹⁰, Jiquan Chen¹¹, Jinshu Chi¹², Ankur R Desai¹³, Allison L Dunn¹⁴, Eugenie Susanne Euskirchen¹⁵, Thomas Friborg¹⁶, Lawrence B Flanagan¹⁷, Inke Forbrich¹⁸, Achim Grelle¹⁹, Silvie R Harder²⁰, Michal Heliasz²¹, Elyn Humphreys²², Hiroki Ikawa²³, Hiroki Iwata²⁴, Pierre-Erik Isabelle²⁵, Rachhpal Jassal²⁶, Juliya Kurbatova²⁷, Mika Korkiakoski²⁸, Lars Kutzbach²⁹, Anders Lindroth³⁰, Takeshi Ohta³¹, Mikaell Ottosson Lofvenius³², Annalea Lohila⁶, Trofim C Maximov³³, Ivan Mammarella³⁴, Philip Marsh³⁵, Joe Melton³⁶, Paul Moore³⁷, Daniel Nadeau²⁵, Erin M Nicholls¹⁰, Mats B Nilsson³⁸, Matthias Peichl³⁹, Richard M Petrone⁴⁰, Roman E Petrov⁴¹, William L Quinton⁴², Nigel T Roulet⁴³, David E Reed⁴⁴, Benjamin Runkle⁴⁵, Anna Rutgersson⁴⁶, Erik Sahlee⁴⁶, Oliver Sonnentag⁴⁷, Ian B Strachan²⁰, Pierre Taillardat⁴⁸, Eeva-Stiina Tuittila⁴⁹, Juha-Pekka Tuovinen⁶, Jess Turner⁵⁰, Masahito Ueyama⁵¹, Andrej Varlagin²⁷, Martin Wilmking⁵² and Steven C Wofsy⁵³, (1)McMaster University, School Of Geography & Earth Sciences, Hamilton, ON, Canada, (2)McMaster University, Hamilton, ON, Canada, (3)University of Helsinki, Department of Physics, Helsinki, Finland, (4)Natural Resources Institute Finland, Helsinki, Finland, (5)Univ Manitoba, Winnipeg, MB, Canada, (6)Finnish Meteorological Institute, Helsinki, Finland, (7)Environment Canada, Climate Research Division, Saskatoon, SK, Canada, (8)University of British Columbia, Soil Science, Vancouver, BC, Canada, (9)University of Colorado, Boulder, Boulder, CO, United States, (10)McMaster University, School of Geography and Earth Sciences, Hamilton, ON, Canada, (11)Michigan State University, Department of Geography, Environment, and Spatial Sciences, East Lansing, MI, United States, (12)SLU Swedish University of Agricultural Sciences Umea, Umeå, Sweden, (13)University of Wisconsin Madison, Department of Atmospheric and Oceanic Sciences, Madison, WI, United States, (14)Worcester State University, Worcester, MA, United States, (15)University of Alaska Fairbanks, Fairbanks, AK, United States, (16)University of Copenhagen, Department of Geosciences and Natural Resource Management, Copenhagen, Denmark, (17)Univ Lethbridge, Lethbridge, AB, Canada, (18)Marine Biological Lab, Woods Hole, MA, United States, (19)SLU Swedish University of Agricultural Sciences Uppsala, Uppsala, Sweden, (20)McGill University, Montreal, QC, Canada, (21)Lund University, Physical Geography and Ecosystem Sciences, Lund, Sweden, (22)Carleton University, Ottawa, ON, Canada, (23)International Arctic Research Center, Fairbanks, AK, United States, (24)Shinshu University, Matsumoto, Japan, (25)Laval University, Civil and Water Engineering, Quebec City, QC, Canada, (26)University of British Columbia, Biometeorology and Soil Physics Group, Vancouver, BC, Canada, (27)A.N. Severtsov Institute of Ecology and Evolution, Russian Academy of Sciences, Moscow, Russia, (28)Greenbrae, CA, United States, (29)Universität Hamburg, Center for Earth System Research and Sustainability, Institute of Soil Science, Hamburg, Germany, (30)Lund University, Lund, Sweden, (31)Nagoya University, Graduate School of Bioagricultural Sciences, Nagoya, Japan, (32)SLU Swedish University of Agricultural Sciences Umeå, Umeå, Sweden, (33)Institute for Biological Problems of the Cryolithozone, Siberian Branch, Russian Academy of Science, Yakutsk, Russia, (34)University of Helsinki, Institute for Atmospheric and Earth System Research / Physics, Faculty of Science, Helsinki, Finland, (35)Wilfrid Laurier University, Cold Regions Research Centre, Waterloo, ON, Canada, (36)Environment and Climate Change Canada, Climate Processes Section, Victoria, BC, Canada, (37)McMaster University, Geography and Earth Sciences,, Hamilton, ON, Canada, (38)Swedish Univrsity of Agricultu, Umeä, Sweden, (39)SLU Swedish University of Agricultural Sciences Umeå, Department of Forest Ecology and Management, Umeå, Sweden, (40)University of Waterloo, Geography and Environmental Management, Waterloo, ON, Canada, (41)Institute for Biological Problems of Cryolithozone, Siberian Branch of Russian Academy of Sciences, Yakutsk, Russia, (42)Wilfrid Laurier University, Geography and Environmental Studies, Waterloo, ON, Canada, (43)McGill Univ, Montreal, QC, Canada, (44)Michigan State University, Center for Global Change and Earth Observations, East Lansing, MI, United States, (45)University of Arkansas, Fayetteville, AR, United States, (46)Uppsala University, Uppsala, Sweden, (47)Université de Montréal, Département de Géographie, Montréal, QC, Canada, (48)University of Quebec at Montreal UQAM, Montreal, Canada, (49)University of Eastern Finland, School of Forest Sciences, Joensuu, Finland, (50)University of Wisconsin Madison, Madison, United States, (51)Osaka Prefecture University, Sakai, Japan, (52)University of Greifswald, Greifswald, Germany, (53)Harvard University, School of Engineering and Applied Sciences, Cambridge, MA, United States