A spatial description of climatic changes along circumpolar regions is presented based on larch tree-ring width (TRW) index, latewood density (MXD), d O ice core record from Greenland (GISP2). Correlation analysis showed a strong positive relationships between TRW, MXD, stable isotope chronologies and June, July air temperatures for TAY and YAK, while the precipitation signal was reflected differently in tree-ring parameters and stable isotope data for the studied sites. Negative correlations were found between July, August precipitation from TAY and stable isotopes and MXD, while May, July precipitations are reflected in MXD and stable isotopes for the YAK. No significant relationships were found between TRW and precipitation for TAY and YAK. The areas of significant correlations between July gridded temperatures and TRW, MXD and stable isotopes show widespread dimension from east to west for YAK and from north to south for TAY. The climate signal is stronger expressed in whole wood than in cellulose for both Siberian regions. The comparison analysis between d 13 C cellulose chronologies from FIN and TAY revealed a similar declining trend over recent decades, which could be explained by the physiological effect of the increasing atmospheric CO 2 . TRW, MXD and d

[1] We related tree ring width (TRW) and isotopic composition (d 13

A brief review is presented of the progress, to date, in constructing a long, continuous ring-width chronology from living and subfossil Siberian larch (Larix gmelinii) in the eastern part of the Taimyr peninsula. A near 2500-year chronology running up to the present has been assembled and several shorter, earlier series have been produced that are dated approximately on the basis of radiocarbon dates. A description is given of the production of separate early summer and annual mean temperature histories based on the recent chronology, spanning more than 2000 years. These two reconstructions are based on alternative methods of statistical processing of the measured tree-ring data. The early summer and annual reconstructions agree well in the longterm components of their variability, providing evidence for anomalous warmth in the third, tenth to twelfth, and twentieth centuries, and a prolonged cool period throughout the sixteenth and seventeenth, and in the early nineteenth centuries. The mean growth and other statistical parameters of the earlier chronologies also suggest that conditions for tree growth were very favourable in the earlier Holocene, particularly in the fourth millennium bc. This is strongly indicative of an early Holocene Climatic Optimum in Taimyr at that time. Other material in hand, and earlier published radiocarbon dates, demonstrate the feasibility of constructing continuous ring-width chronologies and temperature estimates extending throughout all of the last 8000 years.

Tree-ring width of Larix gmelinii (Rupr.) Rupr., ratios of stable isotopes of C (delta(13)C) and O (delta(18)O) of whole wood and cellulose chronologies were obtained for the northern part of central Siberia (Tura, Russia) for the period 1864-2006. A strong decrease in the isotope ratios of O and C (after atmospheric delta(13)C corrections) and tree-ring width was observed for the period 1967-2005, while weather station data show a decrease in July precipitation, along with increasing July air temperature and vapor pressure deficit (VPD). Temperature at the end of May and the whole month of June mainly determines tree radial growth and marks the beginning of the vegetation period in this region. A positive correlation between tree-ring width and July precipitation was found for the calibration period 1929-2005. Positive significant correlations between C isotope chronologies and temperatures of June and July were found for whole wood and cellulose and negative relationships with July precipitation. These relationships are strengthened when the likely physiological response of trees to increased CO(2) is taken into account (by applying a recently developed delta(13)C correction). For the O isotope ratios, positive relationships with annual temperature, VPD of July and a negative correlation with annual precipitation were observed. The delta(18)O in tree rings may reflect annual rather than summer temperatures, due to the late melting of the winter snow and its contribution to the tree water supply in summer. We observed a clear change in the isotope and climate trends after the 1960s, resulting in a drastic change in the relationship between C and O isotope ratios from a negative to a positive correlation. According to isotope fractionation models, this indicates reduced stomatal conductance at a relatively constant photosynthetic rate, as a response of trees to water deficit for the last half century in this permafrost region.

For the first time we present a multi-proxy data set for the Russian Altai, consisting of Siberian larch treering width (TRW), latewood density (MXD), d13 C and d18 O in cellulose chronologies obtained for the period 1779-2007 and cell wall thickness (CWT) for 1900-2008. All of these parameters agree well between each other in the high-frequency variability, while the low-frequency climate information shows systematic differences. The correlation analysis with temperature and precipitation data from the closest weather station and gridded data revealed that annual TRW, MXD, CWT, and d 13 C data contain a strong summer temperature signal, while d18 O in cellulose represents a mixed summer and winter temperature and precipitation signal. The temperature and precipitation reconstructions from the Belukha ice core and Teletskoe lake sediments were used to investigate the correspondence of different independent proxies. Low frequency patterns in TRW and d 13 C chronologies are consistent with temperature reconstructions from nearby Belukha ice core and Teletskoe lake sediments showing a pronounced warming trend in the last century. Their combination could be used for the regional temperature reconstruction. The long-term d18 O trend agrees with the precipitation reconstruction from the Teletskoe lake sediment indicating more humid conditions during the twentieth century. Therefore, these two proxies could be combined for the precipitation reconstruction.

[1] Tree ring width, density, and ratio of stable isotopes ( 13 C/ 12 C and 18 O/ 16 O) in wood and cellulose were determined for larch (Larix sibirica Ledeb.) growing under water deficit conditions in the forest steppe zone in central Siberia (54°24′N, 89°57′E) for the period 1850-2005. Dendroclimatic analysis of the chronologies indicated precipitation to be the most important factor determining indicated parameters. Precipitation of June is significantly correlated with tree ring width and maximum density (r = 0.36 and 0.43, p < 0.05, respectively). Relations of d 13 C and d 18 O to precipitation are similar, but the most important month is July (r = −0.47, p < 0.05 for d 13 C; r = −0.29, p < 0.05 for18 O is positively related to the mean temperatures of July (r = 0.30, p < 0.05). Carbon and oxygen isotope ratios in wood and cellulose showed strong negative trends for the last 100 years. The reason for this decrease could be the observed shift of the beginning of the vegetation period to earlier dates (up to 1 week) in spring and the increased use of precipitation water stored in the soil from October of the previous year, although other explanations cannot be excluded (in particular the physiological effect of increasing atmospheric CO 2 also responsible for lower d13 C values). Thus, an earlier start of the vegetation period could lead to tree ring formation during a period with higher water availability, resulting in stronger isotopic fractionation and 13 C depletion, also reflected in a higher earlywood to latewood ratio. At the same time, highly 18 O depleted water from October precipitation of the previous year is absorbed. The incorporation of this isotopically lighter water during photosynthesis is reflected in the wood and cellulose of tree rings.

We present new tree-ring width, δ 13 C, and δ 18 O chronologies from the Koksu site (49°N, 86°E, 2,200 m asl), situated in the Russian Altai. A strong temperature signal is recorded in the tree-ring width (June-July) and stable isotope (July-August) chronologies, a July precipitation signal captured by the stable isotope data. To investigate the nature of common climatic patterns, our new chronologies are compared with previously published tree-ring and stable isotope data from other sites in the Altai region. The temperature signal preserved in the conifer trees is strongly expressed at local and regional scales for all studied sites, resulting in even stronger temperature and precipitation signals in combined average chronologies compared to separate chronologies. This enables the reconstruction of June-July and July-August temperatures for the last 200 years using tree-ring and stable carbon isotopes. A July precipitation reconstruction based on oxygen isotopic variability recorded in tree-rings can potentially improve the understanding of hydrological changes and the occurrence of extreme events in the Russian Altai.

Newly developed millennial δ13C larch tree-ring chronology from Siberia allows reconstruction of summer (July) vapor pressure deficit (VPD) changes in a temperature-limited environment. VPD increased recently, but does not yet exceed the maximum values reconstructed during the Medieval Warm Anomaly. The most humid conditions in the Siberian North were recorded in the Early Medieval Period and during the Little Ice Age. Increasing VPD under elevated air temperature affects the hydrology of these sensitive ecosystems by greater evapotranspiration rates. Further VPD increases will significantly affect Siberian forests most likely leading to drought and forest mortality even under additional access of thawed permafrost water. Adaptation strategies are needed for Siberian forest ecosystems to protect them in a warming world.