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Project titleClimate reconstruction based on millennia long tree-ring data from Solovki Island.
Project LeadDolgova Ekaterina
AffiliationInstitute of Geography of the Russian Academy of Sciences,
|Implementation period||07.2020 - 06.2022|
Research area 07 - EARTH SCIENCES, 07-701 - Paleogeography
KeywordsDendrochronology, paleoclimate reconstruction, climate response function, last millennium, Solovki Island, tree-ring width, tree-ring maximum density, burried wood, Little Ice Age, Medieval Climate Anomaly
Based on measurements of more than 300 series of Blue Intensity, for the first time in Russia we developed a chronology lasting 1128 (888-2016 CE). The trees included in the final chronology have three different sources. The modern part - about 500 years old - consists of measurements of living trees. Moreover, the life span of pine on Solovki is longer than that of spruce and reaches approximately 500 and 300 years, respectively. The second source of wood in the chronology is samples from wooden elements of buildings. For three years we managed to collect a unique collection of architectural wood, due to which the sample depth was increased in the interval of the 12th-19th centuries. The third group of samples is the drift-wood that we found on Anzer Island. Part of the drift-wood turned out to be quite old and measurements were used to extend the chronology up to 888 CE. Using the DIRECT method, we were able to reconstruction the summer air temperatures and, according to our estimates, the reliable part starts from 1500 CE. It can be stated with confidence that the summer temperature reconstruction we obtained is a quality and sought after product. For three years we have received important conclusions about the climate response, infered from the width and optical density of conifer rings, about the possibility of dating the drift-wood, etc. Continuing work in this direction, we expect to receive new important information about the climate of the past. Comparison of the obtained summer temperature reconstruction with other series available for the Arctic about the climate of the past speaks in favor of the fact that up to 1500 deviations are observed in the dendrochronological series. The causes of deviations may be related to the peculiarity of the method of working with color (and not with a physical volume). Since the early part of the chronology is provided by old samples, whose wood may be dark in color, it is precisely at this period that our reconstruction is not reliable. This problem was partially solved by chemical extraction of substances from the core, as well as measuring not just the optical density, but a difference value that takes into account the color in earlywood too (delta Blue Intensity). Nevertheless, as the results of our work, as well as by some authors (Björklund et al., 2014), show that the optical density may not reliably reflect the low-frequency variation compared to the maximum density, while having a very strong relationship at the interannual level. To solve this specific problem, it was invented to use the delta Blue Intensity Adjusted by calculation method (Björklund et al., 2015). The idea is to measure the areas of sapwood and heartwood separately, calibrating the measurements against the maximum density values. The use of this method has shown very encouraging results in which the BI has ceased to contain sources of color distortion. We propose to carry out such a calibration, due to which we will extend the reconstruction for another several centuries. Instead of maximum density, we propose measuring anatomical density based on cell measurements. The results of the work carried out by comparing the maximum density profiles from different laboratories revealed several important aspects (Björklund et al., 2019). The maximum density, as it turned out, can itself become a source of uncertainties. At low resolution when measuring, the values in narrow rings are underestimated, which also leads to an underestimated trend in the modern period. The problem of equipment calibration is also indicated. These problems can be solved by using anatomical density.
The main result of our research will be the reconstruction of summer air temperatures in Solovki over the past millennium according to dendrochronological data. This result already corresponds to the world level in the field of dendroclimatic research. Our reconstruction has several advantages over others. Firstly, the most significant feature is the tightness of the relationship between optical density and summer temperature. The correlation coefficient reaches 0.75, which is quite rare in dendroclimatic reconstructions. Secondly, the chronology of optical density itself begins in 888; this duration was achieved by including measurements of fin optical density. The significance of such work is obvious, because by creating local reconstructions, ultimately they become part of global climate reconstruction projects both at the regional level (for example, Arctic2k) and at the global level (PAGES). The relevance of our work is also due to the rapid warming in the Arctic, which leads to a change in ecosystems. An analysis of the changes occurring around the world in boreal forests in the width or density of rings can become the basis for many years of monitoring, which began as part of the 2017 RSF project. The long-period variability in the initial period of the chronology turned out to be unreliable, and having solved this problem, we will significantly increase the quality of the final reconstruction. For the first time, a calibration procedure for measuring optical density relative to the anatomical (calculated) density will be carried out for the territory of the ETR.
Annotation of the results obtained in 2021
In the course of the project, we managed to carry out field work on Solovki in order to select new dendrochronological material. We established six new dendrochronological sites based on living pine and spruce trees, whose delta Blue Intensity (dBI) measurements were included in the final chronology. An increase in the length of the chronology at the present stage of the calibration period makes it possible to track the reaction of trees growing on Solovki to modern climate changes. We also focused our attention on finding driftwood that could extend the chronology back centuries. The search was directed to buried trunks lying on the first marine terrace. An additional criterion for selecting samples was the strength of the stems themselves, since too soft (rotten) material cannot be prepared for dBI measurements in a Soxhlet apparatus. Thus, in the summer of 2021, we selected 9 saw cuts located in the north of Anzer Island. We managed to find several soddy trunks covered with grass and moss. We also re-selected a site with 500-year-old pines located on Cape Pechak on Bolshoi Solovetsky Island (B42S and B93S). This material became the basis for cell measurements carried out in 2021. Laboratory processing of samples was carried out according to the algorithm developed by us, namely: resin removal in the Soxhlet apparatus, core surface alignment, scanner calibration, high-resolution scanning and measurement. To obtain the absolute dates of the driftwood, we used dating methods traditional in dendrochronology. The results of cross-dating indicate that the time of death of most of the samples we have selected falls on the middle of the 20th century. The quality of dating of some series is very high. It should be noted that we managed to select samples whose life expectancy reaches several centuries. For example, sample B81p28 reaches 458 years (1469-1926). The time of death of trees is determined by the beginning - the middle of the 19th century, which makes the use of the driftwood very promising. Thus, the results of cross-dating indicate the correctness of the chosen strategy for sampling the driftwood, namely, the location at the maximum possible distance from the seashore and preferably turfiness. The ongoing work on the study of the climate signal continued. It was found that the signal contained in the tree-ring width (TRW) of the pine and spruce is different, although the trees grow in the same habitat. All spruce width parameters (earlywood, latewood, and annual) are sensitive to June temperature variability, and this relationship is stable over the period of instrumental observations (1901-2016). The traditional dendroclimatic analysis of pine width parameters revealed weak correlations for summer temperature and precipitation. Separation into primary and secondary climatic factors revealed a stronger relationship between latewood width and July precipitation (r = 0.4, p<0.05), which makes this parameter attractive for precipitation reconstruction. We also considered how much the response, contained in the parameters of the TRW and dBI of pine and spruce growing in different habitats, changes. All spruce width parameters (earlywood, latewood, and annual) are sensitive to June temperature variability, and this relationship is stable over the period of instrumental observations (1901-2016). The traditional dendroclimatic analysis of pine width parameters revealed weak correlations for summer temperature and precipitation. Separation into primary and secondary climatic factors (in the SeasCorr program) revealed a stronger relationship between latewood width and July precipitation (r = 0.4, p<0.05), which makes this parameter attractive for precipitation reconstruction. As the results of our dendroclimatic analysis have shown, dBI is a parameter on the basis of which a reliable paleoclimatic reconstruction can be obtained. The dBI showed a strong dependence on summer air temperatures (r = 0.6-0.7) and neither the selected coniferous species nor the habitat of the trees practically affects the signal strength. Changes in color in the samples themselves, and especially in the transition area from heartwood to sapwood, affect the trends of the series. To solve the problems described above, we corrected the dBI relative to the anatomical density. We performed sample preparation of 18 pine (B93S) and 18 spruce (B82E) cores. From 18 pine cores, we prepared 104 microsections, which were scanned at ´10 magnification and cut into 4-5 fragments for further analysis in ROXAS (416 images). From the total number of samples, we selected the first 15 pine microsections (60 images), which were about 50-100 years old and were suitable for measuring the cellular parameters of wood. Using a five-step density data correction protocol, we obtained updated values. A comparison of the corrected and original density series revealed the effect of underestimating the dBI values while maintaining the relative amplitude. Judging by the acceptable coefficients regressions obtained at each of the calibration stages, our data are adequate and can be used further. The main result of our project is an updated reconstruction of the summer air temperature based on optical density data. During the reporting period, we continued to conduct experiments on the selection of parameters for the DIRECT program. The method is the author's development of the project participant V.V. Matskovsky and the principle of which is based on the use of a 3D climate response field and avoids the standardization of dendrochronological series (Matskovsky and Helama, 2016). The addition of the set with new measurements made it possible to achieve an improvement in the reconstruction indicators = 0.799, R2 = 0.598, RE = 0.527, CE = 0.445, RMSE = 0.713 In particular, there is good agreement between the reconstruction and instrumental measurements in recent decades, that is, the well-known phenomenon of "divergence" is not observed . We also present an analysis of the influence of large-scale circulation on the variability of air temperature in Solovki. A study of the relationship between SAT in the European North of Russia and SST changes in the North Atlantic, as well as with changes in the large-scale atmospheric circulation of the extratropical zone of the Northern Hemisphere in the second half of the 20th - early 21st centuries, carried out using the method of linear singular value decomposition of covariance matrices, showed the following results . Leading mode SVD analysis of the joint variability of SST in SA with NETR SAT in 1901-2020. and in 1950-2020, which explained 89% and 87% of their variations, respectively, revealed the areas of their most consistent changes in summer. The identified leading mode suggests SST changes in the center of the SA, as well as in the Norwegian and Barents Seas, synchronous with SAT changes in the north of the EPR. It was found that almost a third of the short-period variations of the summer NETR SAT in 1901-2020 was under the control of AMO. By analyzing the structure of the first leading mode of the NETR SAT and Z500 SVD analysis, which explained 89% of their joint summer variability in 1950–2020, the baric centers of the most related changes in altitude pressure with SAT in the north of EPR were identified. It has been established that the strongest influence on the formation of SAT in the summer in the European north of Russia was exerted by changes in pressure over the Eastern Atlantic and over the ETR, which are characteristic of the EA/WR pattern, the leading Eurasia-2 mode.
1. E. A. Cherenkovaa and M. V. Sidorovaa On the Impact of Insufficient Atmospheric Moistening on the Low Annual Discharge of Large Rivers in European Russia Water Resources And the Regime of Water Bodies, Vol. 48, No. 3, pp. 351–360. (year - 2021) https://doi.org/10.1134/S0097807821030064
2. Hadad M. A., González-Reyes Á., Roig, F. A., Matskovsky V., & Cherubini P. Tree-ring-based hydroclimatic reconstruction for the northwest Argentine Patagonia since 1055 CE and its teleconnection to large-scale atmospheric circulation Global and Planetary Change, V.202, P.103496 (year - 2021) https://doi.org/10.1016/j.gloplacha.2021.103496
3. Olga Solomina, Vladimir Matskovsky , Ekaterina Dolgova , Veronika Kuznetsova , Nadezhda Semenyak , Tatiana Bebchuk , Vladimir Mikhalenko , Aleksey Karpukhin , and Bulat Khasanov Tree-ring data set for dendroclimatic reconstructions and dendrochronological dating in European Russia Scientific Data, - (year - 2022)
4. Semenyak N., Solomina O., Dolgova E., Matskovsky V. Климатический сигнал в различных параметрах годичных колец сосны обыкновенной на Соловецком Архипелаге Геосферные исследования, - (year - 2022)
Annotation of the results obtained in 2020
The main goal of the project is to obtain a millenia-long reconstruction based on the Blue Intensity (BI) of conifers growing on the Solovetsky archipelago. Particular attention in the project is paid to the search for old-growth wood, the measurement of which greatly improves the replication in the early period of the chronology. That is why our fieldwork is aimed at studying the driftwood. During the field work in 2020, we managed to select 10 driftwood cuts in the area of the Teriberka village (Kola Peninsula, site B87P). Laboratory preparation and measurement of BI were carried out at the IGRAS tree-ring laboratory. Two samples (B87P1 and B87P7) with a high degree of probability are dated relative to the BI-based Solovki master-chronology to the middle of the 20th century (1837-1979 and 1800-1950, respectively). The dating obtained is also confirmed by comparison with the master chronology of maximum density "Northern Dvina - Pechora". For B87P samples 3, 4 and 9, a floating chronology with a duration of 214 years was built. The highest characteristics (CDI = 36, t-test = 5.7) were found when comparing the floating chronology and the master chronology of the Yenisei. BI, being a relatively new parameter of the tree-ring in dendrochronology field, still requires cross-validation using other methods. To further correct the BI relative to the calculated anatomical, it is necessary to obtain rows of cell structures for 20 samples. All laboratory preparation of samples was carried out by us in the laboratory of biogeochemistry of ecosystems at the Siberian Federal Institute under the leadership of Arsac Peña Alberto Jose. Measurements of the anatomical parameters of conifers were made using the specialized ROXAS software (von Arx, www.wsl.ch/roxas). Before measurements, the samples were calibrated according to the procedure (von Arx et a, 2016). During the last year, we continued to carry out experiments on the selection of parameters for the DIRECT program. The method is the author's development of the project participant V.V. Matskovsky and the principle of which is based on the use of a 3D field of the climatic response and avoids the standardization of dendrochronological series (Matskovsky and Helama, 2016). To simplify the work with the program that implements the DIRECT method, the following functionality has been added: 1) Meta-parameter for selecting the response surface smoothing parameter. 2) Data decimation parameter. A detailed analysis of dendrochronological series of BI used for the reconstruction of air temperature (1184-2016) has been carried out. The results obtained confirm the understanding that the strongest response of the BI of coniferous trees growing in the cold waterlogged conditions of the subarctic landscapes of the forest-tundra is associated with changes in air temperature during the active growing season in late spring and summer. The contribution of air temperature changes during this period to the variability of the growth of BI on Bol'shaya Solovetsky Island in the period 1899-2016. accounted to 63%. Changes in summer precipitation explained 10% of the variability in the BI. The climatic signal in the time series of the growth of tree rings, associated with temperature, which is the leading factor in the production process of the formation of the density of coniferous rings in the study area, is stable over time. A stronger response of the BI of coniferous trees was revealed in the drier period of the first warming in the region in May-August in the middle of the last century compared to the period of modern warming from the beginning of the current century and the observation of more humid conditions of annual atmospheric humidification of the territory. It was found that the extremely high air temperatures for the study region in summer are a favorable rather than a limiting factor for the formation of the BI of conifers in this region. At the same time, extremely low temperatures in summer, observed in more than 10% of the number of summer days, were stressful for trees and, as a rule, led to a decrease in density. Changes in extreme temperature regimes during the summer season explained 47.8% of the variability in tree ring density in 1917-2016. Intra-diurnal changes in extremely warm temperature regimes in summer (for more than 20% of a day in the summer season) in the period under consideration led to the fact that positive anomalies in the density of annual rings, caused by an increase in heat supply, were associated with an increased frequency of occurrence of a large number of extremely warm summer days in the first half of the period, and in the second half - with increased frequency of a large number of extremely warm "white" nights.
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