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Regional growth curves (RGCs) have been recently used to provide a new basis for removing nonclimatic trend from tree-ring data. Here we propose a different use for RGCs and explore their properties along two transects, one meridional and the other elevational. RGCs consisting of mean ring width plotted against cambial age were developed for larch samples from 34 sites along a meridional transect (55–72°N) in central Siberia, and for 24 sites on an elevational gradient (1120 and 2350 m a.s.l.) in Tuva and neighboring Mongolia at approximately 51°N. There are systematic gradients of the parameters of the RGCs, such as I0-maximum tree-ring width near pith, and Imin, the asymptotic value of tree-ring width in old trees. They are smaller at higher latitude and elevation. Annual mean temperature and mean May–September temperature are highly correlated with latitude here, and hence RGC parameters are correlated with these climatic variables. Correlations with precipitation are more complex, and contradictory between meridional and elevational transects. The presence of a similar gradient in the elevational transect is consistent with temperature being the causal factor for both gradients, rather than, for example, latitude-dependent patterns of seasonal photoperiod change. Taking ring measurements from collections of relict and subfossil wood, the RGC–latitude and RGC–temperature relationships are used to estimate paleo-temperatures on centennial time scales. These estimates are consistent with earlier “traditional” dendroclimatic approaches, and with independent information on the northern extent of forest growth in the early mid-Holocene. It may be possible to use this same approach to make estimates of century-scale paleo-temperatures in other regions where abundant relict wood is present. [Copyright &y& Elsevier]

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 long-term 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. [ABSTRACT FROM AUTHOR]

Recently published, improved chronologies for volcanic sulfate in Greenland and Antarctic ice permit a comparison of the growth responses of absolutely annually dated tree rings at three locations in Siberia with annual ice-core records of volcanic eruptions centered on AD 536. For the first time for this region and period, we present unique data sets for tree-ring width, cell-wall thickness, δ 13 C and δ 18 O in cellulose. These were based on multiple samples from relict wood of larch obtained from two sites close to the northern limit of tree growth on the Taimyr Peninsula and in northeastern Yakutia, and at a high-elevation, location 20° further South in the Altai Mts. An event in AD 536 was associated with different, but marked, changes in tree-ring parameters at the high-latitude sites compared with the high elevation site. An AD 541 event was associated with its own distinctive tree-ring responses across the three sites and multiple variables. The years after AD 532 were marked by a strong and sustained decrease in growth at the high-elevation, more southerly, site. The combination of improved ice-core chronology for the climatically effective volcanic eruptions of this part of the 6th century AD, and an array of tree-ring sites with different climates and multiple tree-ring variables permits a richer description of tree responses to this cluster of events. The pattern of tree-ring parameter responses at the three locations in AD 536, AD 541, and perhaps AD 532 is consistent with responses to climatically effective volcanic eruptions influencing tree response in those and subsequent years. [ABSTRACT FROM AUTHOR]

Abstract: To answer the question “Has the recent warming no analogues in the Siberian north?” we analyzed larch tree samples (Larix gmelinii Rupr.) from permafrost zone in the eastern Taimyr (TAY) (72°N, 102°E) using tree-ring and stable isotope analyses for the Climatic Optimum Period (COP) 4111–3806 BC and Medieval Warm Period (MWP) 917–1150 AD, in comparison to the recent period (RP) 1791–2008 AD. We developed a description of the climatic and environmental changes in the eastern Taimyr using tree-ring width and stable isotope (δ13C, δ18O) data based on statistical verification of the relationships to climatic parameters (temperature and precipitation). Additionally, we compared our new tree-ring and stable isotope data sets with earlier published July temperature and precipitation reconstructions inferred from pollen data of the Lama Lake, Taimyr Peninsula, δ18O ice core data from Akademii Nauk ice cap on Severnaya Zemlya (SZ) and δ18O ice core data from Greenland (GISP2), as well as tree-ring width and stable carbon and oxygen isotope data from northeastern Yakutia (YAK). We found that the COP in TAY was warmer and drier compared to the MWP but rather similar to the RP. Our results indicate that the MWP in TAY started earlier and was wetter than in YAK. July precipitation reconstructions obtained from pollen data of the Lama Lake, oxygen isotope data from SZ and our carbon isotopes in tree cellulose agree well and indicate wetter climate conditions during the MWP. Consistent large-scale patterns were reflected in significant links between oxygen isotope data in tree cellulose from TAY and YAK, and oxygen isotope data from SZ and GISP2 during the MWP and the RP. Finally, we showed that the recent warming is not unprecedented in the Siberian north. Similar climate conditions were recorded by tree-rings, stable isotopes, pollen, and ice core data 6000 years ago. [Copyright &y& Elsevier]

A spatial description of climatic changes along circumpolar regions is presented based on larch tree-ring width (TRW) index, latewood density (MXD), δ13C, δ18O of whole wood and cellulose chronologies from eastern Taimyr (TAY) and north-eastern Yakutia (YAK), Russia, for the period 1900–2006, in comparison with a δ13C cellulose chronology from Finland (FIN) and a δ18O 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 δ13C 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 CO2. TRW, MXD and δ13C chronologies from TAY and YAK show a negative correlation with North Atlantic Oscillation index, while the δ18O chronologies show positive correlations, confirming recent warming trend at high latitudes. The strong correlation between GISP2 and δ18O of cellulose from YAK chronologies reflects the large-scale climatic signal connected by atmospheric circulation patterns expressed by precipitation. [ABSTRACT FROM AUTHOR]