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1. Tundra greenness

   https://doi.org/10.1175/BAMS-D-20-0086.  

   Frost, G. V. (December 2020, Bulletin of the American Meteorological Society)

   J. Richter-Menge, M. L. (Ed.)

   Highlights•In North America, tundra productivity for the 2019 growing season (the most recent data available) rebounded strongly from the previous year, in tandem with record summer warmth following the cold summer of 2018.•Since 2016, greenness trends have diverged strongly by continent; peak summer greenness has declined sharply in North America but has remained above the long-term mean in Eurasia.•The long-term satellite record (1982-2019) indicates "greening" across most of the Arctic but some regions exhibit "browning," underscoring the dynamic linkages that exist between tundra ecosystems and other elements of a changing Arctic system. 

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2. The International Tundra Experiment (ITEX): 30 years of research on tundra ecosystems

   https://doi.org/10.1139/as-2022-0041  

   Henry, Greg H.R.; Hollister, Robert D.; Klanderud, Kari; Björk, Robert G.; Bjorkman, Anne D.; Elphinstone, Cassandra; Jónsdóttir, Ingibjörg Svala; Molau, Ulf; Petraglia, Alessandro; Oberbauer, Steven F.; et al (September 2022, Arctic Science)

   The International Tundra Experiment (ITEX) was founded in 1990 as a network of scientists studying responses of tundra ecosystems to ambient and experimental climate change at Arctic and alpine sites across the globe. Common measurement and experimental design protocols have facilitated synthesis of results across sites to gain biome-wide insights of climate change impacts on tundra. This special issue presents results from more than 30 years of ITEX research. The importance of snow regimes, bryophytes, and herbivory are highlighted, with new protocols and studies proposed. The increasing frequency and magnitude of extreme climate events is shown to have strong effects on plant reproduction. The most consistent plant trait response across sites is an increase in vegetation height, especially for shrubs. This will affect surface energy balance, carbon and nutrient dynamics and trophic level interactions. Common garden studies show adaptation responses in tundra species to climate change but they are species and regionally specific. Recommendations are made including establishing sites near northern communities to increase reciprocal engagement with local knowledge holders and establishing multi-factor experiments. The success of ITEX is based on collegial cooperation among researchers and the network remains focused on documenting and understanding impacts of environmental change on tundra ecosystems. 

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3. Tundra photosynthesis captured by satellite-observed solar-induced chlorophyll fluorescence: TUNDRA PHOTOSYNTHESIS AND FLUORESCENCE

   https://doi.org/10.1002/2016GL070842  

   Luus, K. A.; Commane, R.; Parazoo, N. C.; Benmergui, J.; Euskirchen, E. S.; Frankenberg, C.; Joiner, J.; Lindaas, J.; Miller, C. E.; Oechel, W. C.; et al (February 2017, Geophysical Research Letters)
4. The tundra phenology database: More than two decades of tundra phenology responses to climate change

   https://doi.org/10.1139/AS-2020-0041  

   Prevéy, Janet; Elmendorf, Sarah; Bjorkman, Anne; Alatalo, Juha; Ashton, Isabel; Assmann, Jakob; Björk, Robert G.; Björkman, Mats P.; Cannone, Nicoletta; Carbognani, Michele; et al (May 2021, Arctic Science)

   null (Ed.)

   Observations of changes in phenology have provided some of the strongest signals of the effects of climate change on terrestrial ecosystems. The International Tundra Experiment (ITEX), initiated in the early 1990s, established a common protocol to measure plant phenology in tundra study areas across the globe. Today, this valuable collection of phenology measurements depicts the responses of plants at the colder extremes of our planet to experimental and ambient changes in temperature over the past decades. The database contains 150,434 phenology observations of 278 plant species taken at 28 study areas for periods of 1 to 26 years. Here we describe the full dataset to increase the visibility and use of these data in global analyses, and to invite phenology data contributions from underrepresented tundra locations. Portions of this tundra phenology database have been used in three recent syntheses, some datasets are expanded, others are from entirely new study areas, and the entirety of these data are now available at the Polar Data Catalogue (https://doi.org/10.21963/13215). 

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5. The capillaries of the Arctic tundra

   https://doi.org/10.1038/s44221-024-00276-9  

   Liljedahl, Anna K; Witharana, Chandi; Manos, Elias (July 2024, Nature Water)

   Much of the Arctic tundra is underlain by a network of ice wedges that formed during millennia of repeated frost cracking on cold winter days and later infilling of snowmelt water. Growing ice wedges push the soil upwards, forming connected ridges on the ground surface and the ubiquitous ice-wedge polygon tundra. Melting of the top of the ice wedge causes the ground surface to collapse with the rims transforming into snow- and water-collecting troughs — a phenomenon observed at multiple sites across the Arctic tundra in a decade or less. Continued melt establishes a new drainage network only a metre or two wide and less than a half-metre deep, where a doubling of runoff and reduced surface water storage is possible without changes in precipitation. Across the Arctic, lakes are disappearing, while precipitation and river runoff are increasing. So far, the sub-metre microtopographical changes have not entered the scientific analyses encompassing regional and pan-Arctic hydrology. The data and technology are now here to quantify the network of ice wedges across large regions and, though individually small, the ice wedges add up to large numbers. What at first may appear as contradicting hydrological change (for example, shrinking lakes despite increasing precipitation) could be explained by a sudden evolution of the stream network where the new channels are narrow but bountiful: the capillaries of the Arctic tundra hydrological system. 

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