Comparisons of the intrumental, reconstructed (this study) and Gry et al. (2004) reconstructed AMO index on annual and 11-year moving average basis.

<p>(<b>A</b>) Annual comparison of instrumental AMO index <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0022740#pone.0022740-Enfield1" target="_blank">[4]</a> (blue line), the reconstructed proxy series from this study (black line), and <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0022740#pone.0022740-Gray1" target="_blank">[20]</a> tree-ring based AMO reconstruction (red line). (<b>B–D</b>) The above three records smoothed with an 11-year low-pass filter. Red and blue shaded areas represent warm and cold AMO phases respectively. All series (A–D) were normalized by their means and standard deviations. (<b>E</b>) Sample depth in number of cores for the six tree-ring width chronologies.</p

Multi-taper method spectrums for this proxy series from 1564–2007 (A) and the tree-ring AMO reconstruction from Atlantic rim [<b>20</b>] (B).

<p>Significance was tested at three levels (99%, 95% and 90%) against a red-noise background. Digital values are the significant periods at 99% confidence level.</p

Cross correlation between the tree-ring record from northeast Asia and Gray et al. (2004) AMO reconstruction.

<p>Blue horizontal line represents a 95% significance level tested by Pearson correlation analysis.</p

Site information and general statistics of six Scots pine tree-ring chronologies in northeast Asia.

<p>Notes: MS-Mean sensitivity; SD-Standard deviation; AC1-Autocorrelation order 1; MC-Mean correlation; SNR-Signal-to-noise ratio; EPS-Expressed population signal; VFE-Variance in first eigenvector.</p

Comparison of PDSI for the warm and cold AMO phases at six nearby sampling sites.

<p>Comparison of PDSI for the warm and cold AMO phases at six nearby sampling sites.</p

Map of correlation between annual mean precipitable water and annual AMO index (1948–2007) across northeast Asia.

<p>Country boundaries for Russia, Mongolia, and northeast China are shown on the map. It is plotted by the NOAA/ESRL Physical Science Division, Boulder Colorado (<a href="http://www.esrl.noaa.gov" target="_blank">http://www.esrl.noaa.gov</a>). Letters on the map represent different tree-ring sampling sites: <b>A</b> – Zhigansk, <b>B</b> –Khotugn, <b>C</b> – Tschita, <b>D</b> – Taksimo, <b>E</b> – Mangui, <b>F</b> – Mengkeshan. Triangles, circles, and squares represent sampling sites, PDSI points, and weather stations, respectively. Differents colors represent different correlation coefficients marked as the legend at the bottom of the map. The figure on a contour represents the correlation coefficient of this contour.</p

Correlation coefficients of monthly AMO index and six tree-ring chronologies (1856–2007).

<p>Notes: Bolded values for significance at the 95% confidence level as tested by Pearson correlation.</p

Cross wavelet transforms of this proxy series and the AMO index [<b>4</b>] (upper panel) and [<b>20</b>] tree-ring based AMO index (lower panel).

<p>The 95% significance level against red noise is shown as a black contour. The relative phase relationship is shown as arrows (with in-phase pointing right, anti-phase pointing left, and tree-ring index leading AMO by 90° pointing straight down).</p