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1. Arctic shrub colonization lagged peak postglacial warmth: Molecular evidence in lake sediment from Arctic Canada

   https://doi.org/10.1111/gcb.14836  

   Crump, Sarah E.; Miller, Gifford H.; Power, Matthew; Sepúlveda, Julio; Dildar, Nadia; Coghlan, Megan; Bunce, Michael (October 2019, Global Change Biology)
2. Enhanced shrub growth in the Arctic increases habitat connectivity for browsing herbivores

   https://doi.org/10.1111/gcb.15104  

   Zhou, Jiake; Tape, Ken D.; Prugh, Laura; Kofinas, Gary; Carroll, Geoff; Kielland, Knut (July 2020, Global Change Biology)

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3. A narrow window of summer temperatures associated with shrub growth in Arctic Alaska

   https://doi.org/10.1088/1748-9326/ab897f  

   Andreu-Hayles, Laia; Gaglioti, Benjamin V; Berner, Logan T; Levesque, Mathieu; Anchukaitis, Kevin J; Goetz, Scott J; D’Arrigo, Rosanne (October 2020, Environmental Research Letters)

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4. Nitrogen fixing shrubs advance the pace of tall-shrub expansion in low-Arctic tundra

   https://doi.org/10.1038/s43247-023-01098-5  

   Schore, Aiden I.; Fraterrigo, Jennifer M.; Salmon, Verity G.; Yang, Dedi; Lara, Mark J. (December 2023, Communications Earth & Environment)

   Abstract Tall deciduous shrubs are critically important to carbon and nutrient cycling in high-latitude ecosystems. As Arctic regions warm, shrubs expand heterogeneously across their ranges, including within unburned terrain experiencing isometric gradients of warming. To constrain the effects of widespread shrub expansion in terrestrial and Earth System Models, improved knowledge of local-to-regional scale patterns, rates, and controls on decadal shrub expansion is required. Using fine-scale remote sensing, we modeled the drivers of patch-scale tall-shrub expansion over 68 years across the central Seward Peninsula of Alaska. Models show the heterogeneous patterns of tall-shrub expansion are not only predictable but have an upper limit defined by permafrost, climate, and edaphic gradients, two-thirds of which have yet to be colonized. These observations suggest that increased nitrogen inputs from nitrogen-fixing alders contributed to a positive feedback that advanced overall tall-shrub expansion. These findings will be useful for constraining and projecting vegetation-climate feedbacks in the Arctic. 

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5. Arctic Cyclone Activity and the Beaufort High

   https://doi.org/10.1175/JCLI-D-20-0771.1  

   Kenigson, Jessica S.; Timmermans, M.-L. (May 2021, Journal of Climate)

   null (Ed.)

   Abstract The Beaufort high (BH) and its accompanying anticyclonic winds drive the Arctic Ocean’s Beaufort Gyre, the major freshwater reservoir of the Arctic Ocean. The Beaufort Gyre circulation and its capacity to accumulate or release freshwater rely on the BH intensity. The migration of Nordic seas cyclones into the Arctic has been hypothesized to moderate the strength of the BH. We explore this hypothesis by analyzing reanalysis sea level pressure fields to characterize the BH and identify and track cyclones north of 60°N during 1948–2019. A cluster analysis of Nordic seas cyclone trajectories reveals a western pathway (through the Arctic interior) associated with a relatively weak BH and an eastern pathway (along the Arctic periphery) associated with a relatively strong BH. Furthermore, we construct cyclone activity indices (CAIs) in the Arctic and Nordic seas that take into account multiple cyclone parameters (number, strength, and duration). There are significant correlations between the BH and the CAIs in the Arctic and Nordic seas during 1948–2019, with anomalously strong cyclone activity related to an anomalously weak BH, and vice versa. We show how the Arctic and Nordic seas CAIs experienced a regime shift toward increased cyclone activity between the first four decades analyzed (1948–88) and the most recent three decades (1989–2019). Over the same two time periods, the BH exhibits a weakening. Increased cyclone activity and an accompanying weakening of the BH may be consistent with expectations in a warming Arctic and have implications for Beaufort Gyre dynamics and freshwater. 

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