Reconstruction of summer Palmer Drought Severity Index from δ13C of larch tree rings in East Siberia

We present a dendroclimatic reconstruction of Palmer Drought Severity Index (PDSI) in Yakutsk (62 degrees 14'N, 129 degrees 37'E), East Siberia using a larch tree-ring (latewood) delta C-13 chronology (1780-2008 AD). The correlation function analysis showed significant positive correlations between earlywood, latewood and total ring width and July PDSI of the previous summer. On the other hand, tree-ring delta C-13 from earlywood, latewood and total ring showed significant negative correlations with July PDSI in current summer, of which latewood delta C-13 showed highest correlation with PDSI. A moving-window correlation analysis demonstrated that the temporal stability in correlation between tree-ring variables and PDSI was highest when July PDSI was compared with latewood delta C-13. Tree-ring delta C-13 values were corrected by taking account of both the changes in the isotope ratio of atmospheric CO2 (delta C-13(a)) and the plant physiological response to changes in atmospheric CO2 concentration (C-a). This correction significantly improved the sensitivity of larch tree-ring delta C-13 to PDSI, demonstrating that the correction is useful in building a reliable model to estimate past changes in PDSI. Our study shows that larch tree-ring delta C-13 has enough potential to reconstruct July PDSI series. Using a liner regression model, July PDSI was reconstructed from latewood delta C-13 over the last 229 years. The reconstruction showed an interannual to decadal wet/dry fluctuation with a decreasing trend from 1780 to 1960, suggesting that aridification progressed at least after the late Little Ice Age in East Siberia to the modern period of global warming. (C) 2012 Elsevier Ltd and INQUA. All rights reserved.