Abrupt changes in atmospheric methane at the MIS 5b–5a transition

New ice core analyses show that the prominent rise in atmospheric methane concentration at Dansgaard-Oeschger event 21 was interrupted by a century-long 20% decline, which was previously unrecognized. The reversal was found in a new ∼100-year resolution study of methane in the GISP2 ice core, encompassing the beginning of D-O event 21, which also corresponds to the transition from MIS 5b to 5a. Although a corresponding reversal (within age uncertainty) is observed in climate proxies measured in GISP2 ice, including δ¹⁸O[subscript ice], electrical conductivity, light scattering, and several ions, this feature has not been discussed previously. Abrupt changes in methane are paralleled by changes in δ¹⁵N of trapped air, a quantity that reflects local temperature change at Greenland summit. The reversal described here supports the hypothesis that climate can be unstable during major transitions, as was previously described for the last deglaciation.This is the publisher’s final pdf. The published article is copyrighted by the American Geophysical Union and can be found at: http://www.agu.org/journals/gl

Relative timing and variability of atmospheric methane and GISP2 oxygen isotopes between 68 and 86 ka

The global biogeochemical cycle of methane has received wide attention because of methane's role as a greenhouse gas. Measurements of methane in air trapped in Greenland ice cores provide a high-resolution record of methane levels in the atmosphere over the past ~100 ka, providing clues about what controls the methane cycle on geologic timescales. Remarkable similarity between local temperature recorded in Greenland ice cores and changes in global methane concentrations has been noted in previous studies, with the inference that the local temperature variations have global significance, but the resolution of sampling and measurement precision limited fine-scale comparison of these variables. In this work a higher-precision (~2 ppb) methane data set was obtained from the Greenland Ice Sheet Project 2 (GISP2) ice core for the time interval between 86 and 68 ka, encompassing three large abrupt warming events early in the last glacial period: Dansgaard-Oeschger (D-O) events 19, 20, and 21. The new data set consists of duplicate measurements at 158 depths, with average time resolution of 120 years. Such detailed measurements over D-O 21, the longest in Greenland records, have not yet been reported for other ice cores. The new data set documents short-term variability (~20 ppb typical amplitude), which is remarkably persistent, and in many cases similar features are observed in the most detailed published δ¹⁸O[subscript ice] record. High-precision GISP2 δ¹⁵N data show that changes in Greenland temperature are synchronous with the methane variations at the onset of D-O events 19, 20, and 21, supporting previous results from the Greenland Ice Core Project ice core for D-O 19 and 20. Cross-spectral analysis quantifies the extremely close similarity between the new methane record and the δ¹⁸O[subscript ice] record. Because methane sources are widely distributed over the globe, this work further validates δ¹⁸O[subscript ice] at Greenland summit as a geographically broad climate indicator on millennial to multicentennial timescales.Keywords: methane, Dansgaard-Oeschger events, ice core

Tree-Ring Structure of the Pinus sibirica and Pinus cembra Grafts as a Reflection of the Interaction of Scion and Rootstock

Проведен анализ анатомических характеристик годичных колец у подвоев P. sylvestris L. и привоев двух климатипов P. sibirica Du Tour (емельяновского и сургутского) и одного климатипа P. cembra L. (карпатского) за 10 лет их совместного роста. У привоев P. sibirica относительно контрольных деревьев увеличивается число трахеид, их радиальный диаметр и толщина клеточной стенки (кроме клеточной стенки сургутских привоев). В то же время в годичных кольцах подвоев P. sylvestris число трахеид и размеры данных характеристик уменьшаются относительно контрольных деревьев. Исключение составляет сосна обыкновенная, являющаяся подвоем для привоев сургутского климатипа, у которой радиальный диаметр трахеид переходной зоны увеличивается. Сезонная динамика радиального диаметра трахеид и толщины клеточной стенки привитых деревьев сохраняет свою видовую особенность, характерную для непривитых деревьев, что свидетельствует о стабильности генетической программы дифференциации ксилемы. Адаптация привоев к климатическим условиям их места происхождения не влияет на анатомическую структуру годичных колец подвоев в годы, близкие по условиям к климату региона происхождения привоевThe analysis of the anatomical characteristics of tree rings of P. sylvestris L. rootstocks and scions of P. sibirica Du Tour (Emelianovo and Surgut provenances) and P. cembra L. (Karpat provenance) has been carried out for 10 years of their joint growth. The number of tracheids, their radial diameter and the cell wall thickness for the P. sibirica scions increases relative to control trees (with the exception of the cell wall thickness for Surgut scions). At the same time, in the annual rings of the P. sylvestris rootstocks these characteristics as well as the number of tracheids decrease relative to the control trees. An exception is the Scots pine, which is the rootstock for Surgut provenance scion, for which the radial tracheid diameter of the transition zone increases. The seasonal dynamics of the radial tracheid diameter and the cell wall thickness of the grafted trees retains the species features typical for the ungrafted trees, suggesting the stability of the genetic program of xylem differentiation. The adaptation of scions to the climatic conditions of their place of origin does not affect the anatomical structure of the tree rings of the rootstocks during the years in which the conditions are close to the climate of the region of origin of the scion

Annual Sedimentary Record From Lake Donguz-Orun (Central Caucasus) Constrained by High Resolution SR-XRF Analysis and Its Potential for Climate Reconstructions

Bottom sediments of the proglacial Lake Donguz-Orun situated at ∼2500 m a.s.l. in the Elbrus Region (Central Caucasus) reveal regular laminae, characteristic of proglacial varved lakes. This is the first laminated sediment sequence recorded in the region. However, visual counting of the layers was restricted due to partial indistinctness of the lamination. In order to confirm the annual sedimentary cyclicity and proceed with annually resolved data, in addition to the visual identification we used high-resolution geochemical markers. The upper 160 mm of the sediment core were scanned at 200 μm intervals using synchrotron radiation X-ray fluorescence analysis (SR-XRF). Additional ultrahigh resolution scanning at 30 μm increments was employed for the upper 20 mm of the core. The Rb/Sr and Zr/Rb ratios are interpreted to record annual changes in grain-size. Based on this geochemical assessment, we identified 88 annual layers covering the interval between 1922 and 2010, while visually we have been able to identify between 70 and 100 layers. The correctness of the geochemical results is confirmed by mean accumulation rates assessed by 137Cs and 210Pb dating. Cross-correlation between the ring width of local pine chronology and the layer thickness, identified as a distance between the annual Rb/Sr peaks, allowed for the accurate dating of the uppermost preserved year of the sediment sequence (AD 2010). Annually averaged elemental data were then compared with regional meteorological observations, glacier mass balance and tree-ring chronologies. The comparison revealed notable conformities: content of bromine is positively correlated with annual temperatures (r = 0.41, p < 0.01), content of terrigenous elements (major elements with the origin in watershed rocks) is positively correlated (up to r = 0.44, p < 0.01) with annual precipitation. A high statistically significant negative relationship is observed between the concentrations of terrigenous elements and tree-ring width of local pine chronology (up to r = -0.56, p < 0.01). Taken together, these data point to a common composite climatic signal in the two independent records (lake sediments and tree rings) and confirm that the laminae represent annual layers (i.e., varves). These findings open opportunities for high-resolution multiproxy climate reconstructions 300–350 years long using the longer sediment core and tree-ring records

Methodology for Development of a 600-Year Tree-Ring Multi-Element Record for Larch from the Taymir Peninsula, Russia

We developed a long (600-year) dataset for the concentrations of 26 elements in tree rings of larch from the Taymir Peninsula, the northernmost region in the world (ca. 72°N) where trees grow. Tree rings corresponding to the time period from 1300 to 1900 A.D. were studied. Eleven wood strips, each from a different larch tree, were cut into ca. 100 mg samples usually consisting of ten consecutive tree rings (but occasionally five). Between 19 and 40 consecutive samples resulted from each tree, yielding a total of 277 samples. The replication of each time interval ranged from three (for periods 1300-1400 A.D. and 1600-1700 A.D.) to six (for 1450-1600 A.D.). Wood samples were digested with concentrated HNO 3 for measurement of Li, B, Na, Mg, Al, Si, P, Cl, K, Ca, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, As, Rb, Sr, Y, Zr, Nb, Mo, Ag, Cd, Sn, Sb, I, Ba, La, Ce, Nd, W, Au, Pb, Bi, Th, and U using solution Inductively Coupled Plasma Mass Spectrometry (ICPMS). Fourteen elements (V, Co, As, Y, Nb, Mo, Sb, La, Ce, Nd, W, Au, Th, and U) with extremely low concentrations were eliminated from consideration as unreliable. Here we report our sample preparation and measurement procedure, as well as the observed concentrations in tree rings, emphasizing considerations for developing representative and reliable denrodochemical datasets.Нами был получен длительный массив данных (600 лет) концентраций 26 элементов в годичных кольцах лиственницы с полуострова Таймыр, самого северного региона в мире (около 72° с.ш.), где возможен рост деревьев. Изучались годичные кольца, соответствующие промежутку времени с 1300 по 1900 год н.э. Одиннадцать древесных выпилов, по одному для каждой лиственницы, нарезались на образцы массой около 100 мг, которые, как правило, состояли из десяти годичных колец (но в некоторых случаях из пяти). Из каждого дерева было получено от 19 до 40 последовательных образцов, что дало в общей сложности 277 образцов. Повторность для каждого временного интервала варьировала от трех (для периодов 1300-1400 г.н.э. и 1600-1700 г.н.э.) до шести (для периода 1450-1600 г.н.э.). Древесные образцы растворяли в концентрированной HNO 3 для последующего измерения Li, B, Na, Mg, Al, Si, P, Cl, K, Ca, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, As, Rb, Sr, Y, Zr, Nb, Mo, Ag, Cd, Sn, Sb, I, Ba, La, Ce, Nd, W, Au, Pb, Bi, Th и U при помощи масс-спектрометрии с индуктивно связанной плазмой (ICP-MS) для растворов. Четырнадцать элементов (V, Co, As, Y, Nb, Mo, Sb, La, Ce, Nd, W, Au, Th и U) с очень низкими концентрациями были исключены из рассмотрения как недостоверные. В данной статье, основной целью которой являлась отработка методики получения репрезентативных и достоверных дендрохимических данных, приводится использованная нами процедура пробоподготовки и измерений, а также полученные концентрации в годичных кольцах

Variation of the hydrological regime of Bele-Shira closed basin in Southern Siberia and its reflection in the radial growth of Larix sibirica

This study analyses dynamics of the hydrological regime of Bele-Shira closed basin and evaluates the potential for using radial growth of Siberian larch (Larix sibirica) for its assessment. We investigated the relationships between different characteristics of the water level variation of Lake Shira, precipitation amount and long-term regional chronologies developed from 56 living trees and 32 dead trees on three sites across this basin. Graphical and correlation analysis indicate that the interannual change (June minus previous June) of the water level of Lake Shira is strongly positively related to the annual sum of precipitation from July to June and the radial growth of larch. It was shown that this hydrological characteristic integrates the current dynamics of the regional precipitation and moisture regime as a whole of the Bele-Shira closed basin on interannual and decadal scales. The water level of Lake Shira fluctuates on a multi-year timescale in synchrony with the cumulative sum of the tree-ring chronology and also has strong positive long-term trend, probably driven by the continual groundwater inflow from neighboring Lake Itkul. Delayed relationships of precipitation and radial growth with the Lake Shira level change are interpreted with reference to a water balance model of the closed basin. Results offer the possibility of reconstructing interannual and decadal variation of the hydrological regime during the last few centuries through regression models using tree-ring chronologies or the dynamics of climatic variables recovered from them

Precise timing and characterization of abrupt climate change 8200 years ago from air trapped in polar ice

International audienceHow fast and how much climate can change has significant implications for concerns about future climate changes and their potential impacts on society. An abrupt climate change 8200 years ago (8.2 ka event) provides a test case to understand possible future climatic variability. Here, methane concentration (taken as an indicator for terrestrial hydrology) and nitrogen isotopes (Greenland temperature) in trapped air in a Greenland ice core (GISP2) are employed to scrutinize the evolution of the 8.2 ka event. The synchronous change in methane and nitrogen implies that the 8.2 ka event was a synchronous event (within ±4 years) at a hemispheric scale, as indicated by recent climate model results [Legrande, A. N., Schmidt, G. A., Shindell, D. T., Field, C. V., Miller, R. L., Koch, D. M., Faluvegi, G., Hoffmann, G., 2006. Consistent simulations of multiple proxy responses to an abrupt climate change event. Proceedings of the National Academy of Sciences 103, 837–842]. The event began with a large-scale general cooling and drying around 8175±30 years BP (Before Present, where Present is 1950 AD). Greenland temperature cooled by 3.3±1.1 °C (decadal average) in less than 20 years, and atmospheric methane concentration decreased by 80±25 ppb over 40 years, corresponding to a 15±5% emission reduction. Hemispheric scale cooling and drying, inferred from many paleoclimate proxies, likely contributed to this emission reduction. In central Greenland, the coldest period lasted for 60 years, interrupted by a milder interval of a few decades, and temperature subsequently warmed in several steps over 70 years. The total duration of the 8.2 ka event was roughly 150 years

Variation of the hydrological regime of Bele-Shira closed basin in Southern Siberia and its reflection in the radial growth of Larix sibirica

This study analyses dynamics of the hydrological regime of Bele-Shira closed basin and evaluates the potential for using radial growth of Siberian larch (Larix sibirica) for its assessment. We investigated the relationships between different characteristics of the water level variation of Lake Shira, precipitation amount and long-term regional chronologies developed from 56 living trees and 32 dead trees on three sites across this basin. Graphical and correlation analysis indicate that the interannual change (June minus previous June) of the water level of Lake Shira is strongly positively related to the annual sum of precipitation from July to June and the radial growth of larch. It was shown that this hydrological characteristic integrates the current dynamics of the regional precipitation and moisture regime as a whole of the Bele-Shira closed basin on interannual and decadal scales. The water level of Lake Shira fluctuates on a multi-year timescale in synchrony with the cumulative sum of the tree-ring chronology and also has strong positive long-term trend, probably driven by the continual groundwater inflow from neighboring Lake Itkul. Delayed relationships of precipitation and radial growth with the Lake Shira level change are interpreted with reference to a water balance model of the closed basin. Results offer the possibility of reconstructing interannual and decadal variation of the hydrological regime during the last few centuries through regression models using tree-ring chronologies or the dynamics of climatic variables recovered from them

Grafts of Woody Plants and the Problem of Incompatibility Between Scion and Rootstock (a review)

Grafting can occur naturally between branches or more often roots of the same species, or artificially via asexual propagation where the tissues of two plants are encouraged to fuse with one another. Artificial grafting is commonly used for propagation to improve qualities of trees grown commercially via selecting for its roots (called the rootstock) and for stem, leaves, flowers or fruits (called the scion). It is often used to reduce the time to flowering and shorten the breeding program, improve quality and yield of fruits and seeds, improve hardiness in response to environmental conditions and pathogens resistance, and change cultivars. Incompatibility between rootstock and scion has been more often observed for inter-specific than intraspecific grafts, and might result in a dieback of a graft. The objective of this paper was to review the recent literature related to graft applications and incompatibility between scion and rootstock. Anatomical studies of incompatible grafts demonstrated a poor vascular connection, vascular discontinuity and phloem degeneration at the union area, which might be detected as early as few weeks after a graft establishment. These vascular fusion problems can disturb water, nutrient and assimilate flows in the plant and might result in a further breakdown of a union area. Incompatibility might be also a result of insufficient plasmodesmatal coupling at an early stage of development within one of the graft partners. Differences in abundance of phenol compounds and starch below and above the graft union, as well as peroxidase amount at the union might serve as biochemical markers of the rootstock/scion incompatibility. Genetically and biochemically similar scions and rootstocks could improve graft compatibility.Прививки древесных растений могут возникать естественным образом в результате срастания стволов или корней деревьев, находящихся в тесном контакте друг с другом, или искусственно, при пересадке части одного растения, называемого привоем, на другое - подвой. Прививание растений применяется для повышения продуктивности, улучшения качества плодов, ускорения наступления плодоношения, а также повышения резистентности к неблагоприятным факторам среды и патогенам. Из двух видов прививок - гомопластические (внутривидовые) и гетеропластические (межвидовые) - проблемы, связанные с анатомо- физиологической несовместимостью, чаще всего возникают у последних. Целью данной статьи является обзор современной литературы, связанной с применением прививания и проблемой несовместимости между компонентами прививки. На анатомическом уровне несовместимость представляет собой нарушение целостности васкулярных элементов, прерывающихся слоем некротических клеток в зоне контакта привоя и подвоя. В физиологическом отношении неполноценный межклеточный контакт создает барьер, препятствующий доступу воды и минеральных веществ в верхнюю часть растения - привой, и ассимилятов - в противоположном направлении. Несовместимость может быть также результатом нарушения формирования плазмодесм на ранней стадии развития прививки. Различие в концентрации фенольных соединений и крахмала, их избыток ниже и выше зоны срастания компонентов прививки, так же как и пероксидаз, может служить биохимическим маркером несовместимости между привоем и подвоем. Последствия несовместимости привоя и подвоя угнетают рост растения и являются причиной его гибели. Подбор генетически и биохимически сходных компонентов прививки может минимизировать проблему несовместимости