Reconstructed summer Palmer Drought Severity Index since 1850 AD based on d 13 C of larch tree rings in eastern Siberia Shunsuke Tei a,b,⇑ , Hitoshi Yonenobu c , Atsuko Sugimoto b,d , Takeshi Ohta e , Trofim C. Maximov f,g a National Institute of Polar Research, Tokyo 190-0014, Japan b Graduate School of Environmental Science, Hokkaido University, Sapporo, Hokkaido 060-0810, Japan c College of Education, Naruto University of Education, Naruto 772-8502, Japan d Faculty of Environmental Earth Science, Hokkaido University, Sapporo, Hokkaido 060-0810, Japan e Gruduate School of Bioagricultural Sciences, Nagoya University, Nagoya 464-8601, Japan f Institute for Biological Problem of Cryolithozone, Siberian Division of Russian Academy of Science, 41 Lenin Avenue, Yakutsk 678891, Russia g North-Eastern Federal University, 58 Belinskogo St., Yakutsk 677000, Russia article info Article history: Available online xxxx Keywords: Eastern Siberia Taiga Tree ring Carbon isotope PDSI summary We present a tree-ring reconstruction of Palmer Drought Severity Index (PDSI) in Ust-Maya region (60°00 0 N, 133°49 0 E), central part of eastern Siberia using total ring (TR) widths and latewood (LW) d 13 C chronologies from larch trees (1850–2008 AD). Summer (JJA) PDSI was correlated positively and negatively with the TR widths and LW d 13 C, respectively. Using a multiple liner regression approach, we reconstructed summer PDSI using the time series of TR widths and LW d 13 C. The reconstruction showed an interannual to decadal wet/dry fluctuation with several moist periods before 1950s and a sev- ere drought event from 1991 to 1993. Comparison of the reconstruction with reconstructed July PDSI for the Yakutsk region, 300 km northwest of Ust-Maya, showed heterogeneous changes in the mean states of soil moisture, but synchronous year-to-year changes. These results indicate that regional studies are quite important to precisely depict the spatio-temporal variability of hydrological changes in the central part of eastern Siberia. Ó 2015 Elsevier B.V. All rights reserved. 1. Introduction Hydroclimatic records are sparsely available in many parts of the world. Paleohydrological proxies are important for precisely studying the current climate patterns in the long term context and predicting the anticipated changes in the near future. Above all, tree-ring records are the one of the proxies most often used due to their precise time resolution, availability of the records and the potential to extract hydro-climatic information over the past several hundred years (e.g., D’Arrigo et al., 2001; Cook et al., 2010). Soil moisture is the major property of the soil in relation to plant growth, and therefore exerts an important control on the interaction of the hydrosphere, biosphere, and atmosphere. Despite the importance of the soil moisture variability, its nature is poorly understood because of the limitations in length and distribution of instrumental records all over the world (Dai et al., 2004; Dai, 2011). In eastern Siberia, soil moisture records are short and often discontinuous. Although nearly 130 station records of the soil gravimetric measurements are available over the period of 1978–1985 in the International Soil Moisture Network (http:// www.ipf.tuwien.ac.at/insitu/) data sets, longer records of soil moisture or some other hydrological variables are necessary to better understand the current moisture variability for this region. A global data set of Palmer Drought Severity Index (PDSI) (Dai et al., 2004) may serve this purpose. PDSI (Palmer, 1965) was first intended to reflect regional moisture availability and is used wide- ly to study the extent and severity of droughts and wet spells in the United States (e.g., Cook et al., 1999, 2004). Although PDSI does not reflect soil moisture conditions when the soil is frozen, it shows a significant correlation with observed soil moisture for the vegetation period (Dai et al., 2004; Dai, 2011). The global dataset includes a 2.5° latitude/longitude gridded record over eastern Siberia spanning 1888 to 2005. Despite the importance of wide-area tree-ring reconstructions of PDSI, regional studies are still essential to better understand http://dx.doi.org/10.1016/j.jhydrol.2015.01.085 0022-1694/Ó 2015 Elsevier B.V. All rights reserved. ⇑ Corresponding author at: Graduate School of Environmental Science, Hokkaido University, Hokkaido, Japan. Tel.: +81 11 706 2233. E-mail address: stei@ees.hokudai.ac.jp (S. Tei). Journal of Hydrology xxx (2015) xxx–xxx Contents lists available at ScienceDirect Journal of Hydrology journal homepage: www.elsevier.com/locate/jhydrol Please cite this article in press as: Tei, S., et al. Reconstructed summer Palmer Drought Severity Index since 1850 AD based on d 13 C of larch tree rings in eastern Siberia. J. Hydrol. (2015), http://dx.doi.org/10.1016/j.jhydrol.2015.01.085