gcb2507-sup-0001-FigureS1.pdfapplication/PDF447KFigure S1. Standardized ring-width indices (grey lines) and mean site chronologies (black lines) for each site in Old Crow Flats based on signal-free standardization (Melvin & Briffa, 2008) using conservative ‘negative exponential’ or ‘negative-to-zero slope linear’ curve fits (Fritts et al., 1969). Sample depth (red lines) indicates the number of series defining the mean chronology. The mean chronologies were calculated with a robust bi-weight mean (Cook, 1985); more details on each chronology are provided in Table 1.
gcb2507-sup-0002-FigureS2.pdfapplication/PDF299KFigure S2. A comparison of each mean site chronology produced using ‘signal-free’ (black lines) and non-signal-free (red lines) methods. Inter-series differences can be considered the result of ‘trend distortion’ (Melvin & Briffa, 2008). Due to differences in non-age-related growth (i.e., forced by climate, disturbance, etc.) between sites, trend distortion effects are more pronounced in some chronologies (e.g., JC1, OC9, OC54, SC1, and TH1) than in others (e.g., DP26, OC50, OC52, TM1, and TM2).
gcb2507-sup-0003-FigureS3.pdfapplication/PDF323KFigure S3. Magnified comparison of the mean Group 1 and Group 2 chronologies during (a) 1600–1800 and (b) 1800–2000. Smoothed chronologies were calculated using a 15-year cubic smoothing spline with a 50% frequency cut-off (Cook & Peters, 1981).
gcb2507-sup-0004-FigureS4.pdfapplication/PDF213KFigure S4.Old Crow Flats sites: Group 1 (negative temperature response), Group 2 (positive temperature response), and Mixed (mixed negative/positive temperature response).
gcb2507-sup-0005-TableS1.pdfapplication/PDF192KTable S1. Correlations between the 23 Old Crow Flats ‘signal-free’ site chronologies and minimum/maximum temperatures from May to August of the growth year (t) and previous growth year (t−1); only correlations significant at ≤ 0.05 (two-tailed) are presented.
gcb2507-sup-0006-NoteS1.pdfapplication/PDF112KNote S1. A running 2-sample t-test was used to test the null hypothesis that the Group 1 and 2 site chronologies are derived from the same normal distribution with equal means and variance (≤ 0.05). The null hypothesis was tested for each year that both groups contained four or more site chronologies. The t-test result was calculated using the ‘ttest2’ function (Statistics Toolbox) in Matlab 7.4.
gcb2507-sup-0007-NoteS2.pdfapplication/PDF112KNote S2. The Mackenzie Delta East Channel (MDEC) negative-responder (neg) and positive-responder (pos) used here are modified versions of the ‘negative- and positive-responder’ chronologies by Pisaric et al. (2007). The main difference is that the modified MDEC neg and MDEC pos chronologies do not contain Campbell Dolomite Upland (CDU) series (Szeicz & MacDonald, 1996). CDU series were excluded from MDEC neg and MDEC pos to ensure our Group 1/Group 2 correlations with CDU, MDEC neg, and MDEC pos would be independent of each other.
gcb2507-sup-0008-NoteS3.pdfapplication/PDF112KNote S3. The mean NWNA 1/NWNA 2 chronologies were compared with a regional average of CRUTEM3v gridded temperatures (Brohan et al., 2006). The regional average includes 22 (5° × 5°) grid cells bounded by 60–70°N and 170–115°W; only two grid cells (65–70°N/160–155°W and 65–70°N/150–145°W) did not contain any data. Temperature data before 1900 were not used as spatial coverage is limited. The number of grid cells with data for the year 1900 is 5; the number of grid cells increases steadily to more than 10 by the early-1920s, more than 15 by the early-1940s and a high of 20 by 1959.

Please note: Wiley Blackwell is not responsible for the content or functionality of any supporting information supplied by the authors. Any queries (other than missing content) should be directed to the corresponding author for the article.