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Seasonal means of Toolik LTER SAT 1988–2014 for winter (October 1–April 30), spring (May 1–June 15), summer (June 16–August 15), and fall (August 16–September 30). Summer data also include 1996–2014 means from Zackenberg (closed squares) from August 16 to September 30. Trend lines are linear regressions; only Zackenberg summer trends are significant (p < 0.01). Data sources same as in Fig. 2
