Natural Archives Research Articles

Historical record of anthropogenic polycyclic aromatic hydrocarbons in a lake sediment from the southern Tibetan Plateau.

High-altitude lake sediments can be used as natural archives to reconstruct the history of pollutants. In this work, the temporal distribution of polycyclic aromatic hydrocarbons (PAHs) was determined in a sediment core collected from the southern Tibetan Plateau (TP), which was dated by using the 210Pb dating method and validated with the 137Cs fallout peak. The concentrations of the anthropogenic PAHs (Σ8PAH) in the sediment core ranged from 0.83 to 12ng/g dw, and the fluxes of the Σ8PAH were in the range of 2.1-27g/cm2/year. The temporal variations in the concentration and input flux of anthropogenic PAHs were low with little variability before the 1950s, and then gradually increased from the 1950s to the 1980s, and an accelerated increase was observed after the early 1980s. The content of total organic carbon played an insignificant role in affecting the time trends of PAHs in the sediment core. Diagnostic concentration fractions of PAH components indicate PAHs in the lake sediment of the southern TP which are mainly from biomass burning and/or from long-range atmospheric transport.

Fecal biomarker imprints as indicators of past human land uses: Source distinction and preservation potential in archaeological and natural archives

This paper presents the potential of 5β-stanols and bile acids to act as fecal source biomarkers in order to identify and characterize past agropastoral activities in archaeological and natural archives. First of all, a molecular inventory of 5β-stanols and bile acids was made on fresh fecal human and domestic animal samples, using the same methodology to define the specificity of these molecular biomarkers. The selected species were cow, horse, pig and sheep as they are the major domestic species present in European archaeological sites. To our knowledge, our work constitutes the first report on fecal biomarkers in sheep feces. Bile acids can distinguish diet regime and species having the same diet with greater specificity than 5β-stanols. Fresh human fecal material and historical/archaeological fecal material were analyzed to assess their stability through time by calculating the coprostanol/epi-coprostanol (Cp/epi-Cp) and deoxycholic acid/cholic acid (DOC/C) ratios. Results show that bile acids are more resistant to diagenesis than 5β-stanols, at least on a 700-year time scale. Human and domestic animal fecal molecular imprints were then compared to the molecular content of 65 samples retrieved from archaeological sites, soils and lacustrine sediments to test their ability to trace past land-use dynamics. This study is the first to combine bile acids and 5β-stanols to identify a source of fecal material in lacustrine sediments. The combination of sterols and bile acids can be used in a variety of natural archives and archaeological contexts to define the origin of fecal material, to specify land-use, and to reconstruct past pastoral practices at various spatio-temporal scales.

A new CT scan methodology to characterize a small aggregation gravel clast contained in a soft sediment matrix

Abstract. Over the past decades, X-ray computed tomography (CT) has been increasingly applied in the geosciences community. CT scanning is a rapid, non-destructive method allowing the assessment of relative density of clasts in natural archives samples. This study focuses on the use of this method to explore instantaneous deposits as major contributors to sedimentation of high-elevation lakes in the Alps, such as the Lake Lauvitel system (western French Alps). This lake is located within a very steep valley prone to episodic flooding and features gullies ending in the lake. This variety of erosion processes leads to deposition of sedimentary layers with distinct clastic properties. We identified 18 turbidites and 15 layers of poorly sorted fine sediment associated with the presence of gravels since AD 1880. These deposits are respectively interpreted as being induced by flood and wet avalanche. This constitutes a valuable record from a region where few historical records exist. This CT scan approach is suitable for instantaneous deposit identification to reconstruct past evolution and may be applicable to a wider variety of sedimentary archives alongside existing approaches.

Concentrations and origin of polychlorinated biphenyls (PCBs) and polycyclic aromatic hydrocarbons (PAHs) in sediments of western Spitsbergen fjords (Kongsfjorden, Hornsund, and Adventfjorden).

Contaminant profiles in sediment cores represent valuable natural archives of environmental contamination, by which contaminant sources and historical changes in contaminant input and cycling may be recognized. In the present study, we discuss the sedimentary profiles and historical trends of organic contaminants - polychlorinated biphenyls (PCBs) and polycyclic aromatic hydrocarbons (PAHs) - in three fjords of the Svalbard archipelago differing in environmental conditions and anthropogenic impact. The obtained results revealed no significant differences between the fjords Hornsund and Kongsfjorden, in the average levels of the analyzed contaminants. Levels ranging from 0.05 to 1.47ng/g d.w. for ∑7 PCBs and from 37.3 to 1973ng/g d.w. for ∑12 PAHs were measured. The observed spatial and temporal differences in contaminant levels are rather related to local variations in the fjords associated with the location of sampling stations. Higher concentrations of the ∑7 PCBs exceeding 1.00ng/g d.w. were measured in sediment cores collected in the inner parts of both fjords, which remain under the influence of melting glacier outflows. Important concentrations of these contaminants were noticed in layers deposited recently, suggesting intensive supply of these substances from secondary sources. The observed levels are generally low and well below known established no effect levels. Only the concentration of fluoranthene exceeded the threshold effect level at several sampling stations. Moreover, fluoranthene concentrations in almost all Adventfjorden sediment layer samples were above probable effect levels, which can indicate a risk of adverse effects in exposed benthic organisms. The fluoranthene/pyrene and phenthrene/anthracene ratios, which are used for identification of hydrocarbon sources, suggest a dominance of PAHs of pyrolytic genesis in Kongsfjorden and Hornsund. In Adventfjorden, hydrocarbons of petrogenic origin were predominant. However, other sources like coal dust from stores on land are also possible at this location.

Introducing global peat-specific temperature and pH calibrations based on brGDGT bacterial lipids

Glycerol dialkyl glycerol tetraethers (GDGTs) are membrane-spanning lipids from Bacteria and Archaea that are ubiquitous in a range of natural archives and especially abundant in peat. Previous work demonstrated that the distribution of bacterial branched GDGTs (brGDGTs) in mineral soils is correlated to environmental factors such as mean annual air temperature (MAAT) and soil pH. However, the influence of these parameters on brGDGT distributions in peat is largely unknown. Here we investigate the distribution of brGDGTs in 470 samples from 96 peatlands around the world with a broad mean annual air temperature (−8 to 27°C) and pH (3–8) range and present the first peat-specific brGDGT-based temperature and pH calibrations. Our results demonstrate that the degree of cyclisation of brGDGTs in peat is positively correlated with pH, pH=2.49×CBTpeat+8.07 (n=51, R2=0.58, RMSE=0.8) and the degree of methylation of brGDGTs is positively correlated with MAAT, MAATpeat (°C)=52.18×MBT5me′−23.05 (n=96, R2=0.76, RMSE=4.7°C). These peat-specific calibrations are distinct from the available mineral soil calibrations. In light of the error in the temperature calibration (∼4.7°C), we urge caution in any application to reconstruct late Holocene climate variability, where the climatic signals are relatively small, and the duration of excursions could be brief. Instead, these proxies are well-suited to reconstruct large amplitude, longer-term shifts in climate such as deglacial transitions. Indeed, when applied to a peat deposit spanning the late glacial period (∼15.2kyr), we demonstrate that MAATpeat yields absolute temperatures and relative temperature changes that are consistent with those from other proxies. In addition, the application of MAATpeat to fossil peat (i.e. lignites) has the potential to reconstruct terrestrial climate during the Cenozoic. We conclude that there is clear potential to use brGDGTs in peats and lignites to reconstruct past terrestrial climate.

The bark of the branches of holm oak (Quercus ilex L.) for a retrospective study of trace elements in the atmosphere

Tree bark has proved to be a useful bioindicator for trace elements in the atmosphere, however it reflects an exposure occurring during an unidentified period of time, so it provides spatial information about the distribution of contaminants in a certain area, but it cannot be used to detect temporal changes or trends, which is an important achievement in environmental studies. In order to obtain information about a known period of time, the bark collected from the annual segments of tree branches can be used, allowing analyses going back 10–15 years with annual resolution. In the present study, the concentrations of As, Cd, Co, Cu, Fe, Mn, Ni, Pb, V and Zn were measured by atomic emission spectrometry in a series of samples covering the period from 2001 to 2013 in an urban environment. Downward time trends were significant for Cd, Pb and Zn. The only trace element showing an upward time trend was V. The concentrations of the remaining six trace elements were constant over time, showing that their presence in bark is not simply proportional to the duration of exposure. This approach, which is simple, reliable and widely applicable at a low cost, allows the “a posteriori” reconstruction of atmospheric trace element deposition when or where no monitoring programme is in progress and no other natural archives are available.

Historical trends of organochlorine pesticides (OCPs) recorded in sediments across the Tibetan Plateau.

Sediment cores from four lakes across the Tibetan Plateau were used as natural archives to study the time trends of organochlorine pesticides (OCPs). The total concentrations of dichlorodiphenyltrichloroethane (ΣDDT) and hexachlorocyclohexane isomers (ΣHCH) were in the range of 0.04-1.61 and 0.08-1.88ng/g based on dry weight (dw), while the input fluxes were in the range of 0.3-236 and 0.7-295pg/cm2/y in the core sediments, respectively. The input fluxes of ΣDDT and ΣHCH generally peaked in sediment layers corresponding to the 1970s-1990s and peaked in top sediment layers. The ratio of α/γ-HCH decreased in the top layer sediments, implying that the contribution of lindane (pure γ-HCH) has been increasing in recent years. In addition, the ratio of o,p'-DDT/p,p'-DDT increased significantly over the last 15-20years, suggesting that dicofol (characterized by high ratio of o,p'-DDT/p,p'-DDT about 7.0) has recently become a relatively more important source of DDT compared to technical DDT itself. The time trends of OCPs recorded in lake sediments examined the impact on such remote alpine regions by human activities.

Late Quaternary loess-like paleosols and pedocomplexes, geochemistry, provenance and source area weathering, Manasbal, Kashmir Valley, India

The late Quaternary loess and loess-like deposits in Kashmir Valley are natural archives that have preserved paleoclimate and paleoenvironmental records of the region. We present a loess-like paleosol located along the margin of the Manasbal Lake, Ganderbal, which was studied in detail for understanding the pedological processes and reconstructing the late Quaternary soil formation. In this paper we present loess-like paleosol formation of a nearly 10.6m thick sequence exposed along the margin of Manasbal Lake, Ganderbal District, Srinagar, Kashmir. Geochemical and textural data of this loess-like sedimentary sequence fluctuate reflecting the varied depositional processes operating in the valley, differential intensity of weathering, and processes of pedogenesis. Weathering indices such as chemical index of alteration, chemical index of weathering, and plagioclase index of alteration reveal weak to moderate weathering of the parent material. Provenance discrimination diagrams of the present study disclose that the Manasbal loess-like paleosol sediments are derived from the mixed source rocks suggesting a variety of provenance with variable geological settings, which apparently have undergone weak to moderate recycling processes. The Manasbal paleosol horizons have been dated by the optically stimulated luminescence (OSL) method to the marine isotope stages mid-MIS-3 (41.7±8.0ka) and late-MIS-2 (14.6±3.8ka). During the MIS-3 period, the climate was wetter, forming a strong AhBtk paleosol as inferred from the geochemical data. A steady increase in the CaCO3 content and C/N ratio in the paleosols from 6.50m (MIS-3) indicates arid and drier climatic conditions. The area around Manasbal Lake incised because of climate change and neotectonic activity since post-14ka.

The new local interstellar spectra and their influence on the production rates of the cosmogenic radionuclides 10Be and 14C

AbstractWith Voyager1 crossing the outer boundary of our solar system at the end of 2012, for the first time in the instrumental era an unmodulated local interstellar spectrum (LIS) at galactic particle energies below ~500 MeV has been measured. On the basis of these as well as Payload for Antimatter Matter Exploration and Light‐nuclei Astrophysics (PAMELA) and Alpha Magnetic Spectrometer (AMS02) measurements, most recently, three new LIS models have been proposed in the literature. In this study we compare the newest LIS models to previously most often used ones. Thereby, we investigate and discuss the influence of these LIS models on the terrestrial production rates of the cosmogenic radionuclides 10Be and 14C, which are produced due to the interaction of galactic and solar cosmic rays with atmospheric constituents. After being transported within the atmosphere they are preserved in natural archives such as, e.g., ice sheets or tree rings, forming a unique tool to study the solar modulation of thousands of years back in time. To parameterize the heliospheric modulation we apply the force‐field approximation for the individual LIS models from which LIS‐dependent solar modulation parameter (ϕ) values are derived. Furthermore, we present updated sets of linear regression functions containing the opportunity to convert the LIS‐dependent ϕ values between the investigated LIS models. The results are then applied to a long‐term reconstruction of the solar modulation parameter.

Authigenic 10Be/9Be ratio signature of the Matuyama–Brunhes boundary in the Montalbano Jonico marine succession

Geomagnetic dipole moment (GDM) lows associated with polarity reversals or geomagnetic excursions induce significant modulation of the cosmogenic nuclide Beryllium-10 (10Be) production. Hence, the reconstruction of atmospheric 10Be production rates from natural archives such as marine sedimentary sequences or ice cores constitutes a complementary approach, independent from paleomagnetic measurements, to decipher past GDM fluctuations. This is particularly important in the Montalbano Jonico succession (South Italy) since it is candidate to host the Global Stratotype Section and Point of the Middle Pleistocene Stage but where the magnetostratigraphic positioning of the Matuyama–Brunhes boundary (MBB) has not been available up to now. This study presents (1) original authigenic 10Be cosmogenic nuclide and 9Be stable isotope results, and (2) new high-resolution benthic oxygen isotope record covering termination IX and Marine Isotope Stage (MIS) 19. A robust chronological framework is established on the basis of (i) our oxygen isotope stratigraphy, using the strong analogies between MIS 1 and MIS 19c in terms of orbital forcing and CO2 level, and (ii) one precise 40Ar/39Ar date obtained in the tephra layer V4. The authigenic 10Be/9Be ratio record marks the atmospheric 10Be overproduction linked to the dipole low accompanying the MBB transition, with a characteristic twofold increase of the 10Be production at the end of MIS 19c and early MIS 19b. This signature is similar to those described in both marine and ice core records. The detailed chronostratigraphy constrained by a radiometrically-dated tephra layer (773.9±1.3 ka) within the MBB interval, makes it possible to discuss the structure and to assess the timing of the 10Be-production changes, and thus the MBB geomagnetic variations, with an unprecedented accuracy for a marine archive (sedimentation rates ∼80 cm/ka). These new cosmogenic nuclide production signatures provide the only missing constraint required for retaining the Montalbano Jonico succession as a global-scale correlation reference section for the Early–Middle Pleistocene boundary.

Macrofossils analysis of the peat to reconstruct holocene paleoecological conditions about Kansk forest-stepp zone (Yenisey Siberia)

В статье на примере болотного массива «Кускун», расположенного в пойме р.Есауловка (Канская лесостепь) приведены результаты изучения генезиса и эволюции болот северной лесостепи. На основании изучения макрофоссилий торфа, определения зольности и степени разложения, при применении экологических шкал Раменского и Элленберга были реконструированы палеоэкологические условия времени развития болот: дана оценка условий увлажнения за весь период торфонакопления, выделены фазы в развитии болота, описана свойственная им растительность.

Subfossil Cladocera and pollen as indicators of natural and anthropogenic trophic changes of Lake Jelonek (Tuchola Forest, N Poland) during the Holocene

<p class="Tre">Lake Jelonek is a small lake located in central northern Poland, in the Tuchola Forest. The sediments of the lake represent a natural archive that offers insights into the natural history of the region from the Late Glacial to present. In winter 2002, a 1330 cm long sediment core was recovered from the deepest part of lake. Using a multiproxy approach (cladocerans, pollen and basic geochemistry), we reconstructed trophic status changes through the last ~15,000 years. Special attention was devoted to the evaluation of nutrient contributions to the lake from natural and anthropogenic sources. The Cladocera analyses yielded a total of 29 species belonging to five families (Bosminidae, Daphniidae, Leptodoridae, Chydoridae, Sididae), with planktonic species representing more than 60% of Cladocera relative abundance throughout the core. The pollen results suggested four periods of increased human activity, so-called settlement phases. The first traces of human activity in the basin of Lake Jelonek appeared in the Atlantic period and were related with Mesolithic and Neolithic settlements. The second (Bronze Age) and the third (Iron Age) settlement phases are well marked by the paleolimnological proxies studied. This time period clearly manifested on the lake waters as an increasing trophy level probably caused by human-associated discharges of nutrients to the lake. After the third settlement phase cladoceran data indicated a significant decrease in the lake trophic level and the pollen data showed a recovery of forest cover. The fourth period of human economic activity during the early Middle Age was characterized by deforestation associated with land reclamation for grazing and cultivation of cereals, and the subsequent nutrient enrichment of lake waters. According to our results, the biological development of Lake Jelonek was determined by climate changes from Late Glacial up to the Atlantic period. Contrastingly, the most important driver for the lake development though the middle and late Holocene has been human activity within the lake catchment. The recovery of the lake trophic level during the last century, which is primarily related to extensive afforestation of the lake catchment, highlighted the importance of land use in the conservation of healthy water bodies.</p>

Branch bark of holm oak (Quercus ilex L.) for reconstructing the temporal variations of atmospheric deposition of hexavalent chromium

The bark from the annual segments of the branches of holm oak (Quercus ilex L.) is exposed to trace element deposition for a known period of time and thus it is a possible candidate as a bioindicator for reconstructing historical changes in pollution. A series of samples were analysed for Cr(VI) concentration by electrothermal atomic absorption spectrometry (ET-AAS) after selective extraction in a sodium carbonate solution. In this way the atmospheric deposition of Cr(VI) was reconstructed from 2001 to 2010 in an area where an industrial plant produced Cr(VI) compounds until 2003. The present study shows the potential of this type of sample as a natural archive for persistent pollutants, useful for monitoring changes that occur before a monitoring programme is established, with the advantage of being easy to collect almost everywhere.

Reconstructions of the 14С cosmogenic isotope content from natural archives after the last glacial termination

Data on the content of the 14C cosmogenic isotope in tree rings, which were obtained as a result of laboratory measurements, are often used when solar activity (SA) is reconstructed for previous epochs, in which direct observations are absent. However, these data contain information not only about SA variations but also about changes in the Earth climatic parameters, such as the global temperature and the CO2 content in the Earth’s atmosphere. The effect of these variations on the 14C isotope content in different natural reservoirs after the last glacial termination to the middle of the Holocene is considered. The global temperature and the CO2 content increased on this time interval. In this case the 14C absolute content in the atmosphere increased on this time interval, even though the 14С to 12С isotope concentration ratio (as described by the Δ14С parameter) decreased. These variations in the radiocarbon absolute content can be caused by its redistribution between natural reservoirs. It has been indicated that such a redistribution is possible only when the rate of carbon exchange between the ocean and atmosphere depends on temperature. The values of the corresponding temperature coefficient for the 17–10 ka BC time interval, which make it possible to describe the carbon redistribution between the ocean and atmosphere, have been obtained.

Increasing dominance of small zooplankton with toxic cyanobacteria

Summary Cyanobacterial blooms are often associated with an increase in abundance of small‐bodied zooplankton. The hypothesis that toxic cyanobacteria lead to in the dominance of small‐bodied zooplankton was tested by investigating competitive outcomes with three common cladoceran species, analysing cladoceran remains in sediments, and identifying zooplankton resting eggs. Although the large‐bodied cladoceran Daphnia pulex outcompeted the medium‐sized cladoceran Simocephalus vetulus when fed green algae in laboratory experiments, the presence of toxic cyanobacteria completely altered this competitive outcome. Similar shifts in competitive dominance with the presence of cyanobacteria were observed when both D. pulex and S. vetulus competed with the small‐bodied cladoceran Bosmina longirostris. Sediment cores from Dianshan Lake, the largest shallow lake in Shanghai, and surface sediments from 10 random ponds and rivers in the area were collected to recover the cladoceran and total zooplankton communities. Microcystin concentrations in sediments were used as a proxy for cyanobacterial abundances in nature. Altogether, cladoceran remains representing 10 genera were recovered from the sediment samples. Microcystin concentrations in the Dianshan Lake sediment cores were positively correlated with Bosmina abundance, but negatively correlated with both Daphnia and Diaphanosoma abundance. The proportion of large‐bodied cladocerans significantly declined in relation to small‐bodied species with increasing microcystin concentrations in the lake sediments. Fifty‐eight types of zooplankton resting eggs were recovered in sediments from Shanghai waters and identified using DNA barcoding. The abundance of both a lecanid rotifer and total rotifers significantly increased with increasing cyanobacteria in the sediment cores, whereas the dominant copepod, Sinocalanus tenellus, decreased. However, these trends were not observed in comparison of surface sediments from 10 ponds and rivers in the area. These results indicate that the presence of toxic cyanobacteria may have altered the zooplankton communities and contributed to increased dominance of small‐bodied species. This study also demonstrates that cladoceran remains and zooplankton resting eggs recovered from sediment cores are convenient natural archives for evaluating zooplankton responses to cyanobacterial blooms.

Disentangling Natural and Anthropogenic Signals in Lacustrine Records: An Example from the Ilan Plain, NE Taiwan

The impact of human activities has been increasing to a degree where humans now outcompete many natural processes. When interpreting environmental and climatic changes recorded in natural archives on historical time scales, it is therefore important to be able to disentangle the relative contribution of natural and anthropogenic processes. Lake Meihua on the Ilan Plain in northeastern Taiwan offers a particularly suitable opportunity to test how human activities known from historical records can be recorded in lacustrine sediment. For this purpose, three cores from Lake Meihua have been studied by a multiproxy approach, providing the first decadal-resolution lacustrine records covering the past 150 years in Taiwan. Profiles of excess 210Pb, 137Cs and 239,240Pu from two short cores (MHL-09-01 and MHL-11-02) allowed a precise chronology to be established. The presence of a yellow, earthy layer with lower levels of organic material coincide with the record of land development associated with the construction of the San-Chin-Gong Temple during AD 1970-1982. Furthermore, in the lower part of the cores, the upwards increasing trend of inc/coh, TOC, TOC/TN, and grain size, coupled with the palynological data (increase of Alnus, Mallotus, Trema and herbs) from the nearby core MHL-5A with radiocarbon chronology, suggest that the area surrounding the lake has been significantly affected by agricultural activities since the arrival of Chinese settlers around ~AD 1874. In sum, this study demonstrates that this suite of lacustrine sediments in northeastern Taiwan has recorded human activities in agreement with historical documents, and that different human activities will leave distinct sedimentological, geochemical, and palynological signatures in the sedimentary archives. Therefore, multiproxy reconstructions are important to capture the complex nature of human-environmental interactions. A better understanding of the weathering and erosion response to human activities can also provide useful information for sustainable land-use management.

400 Years of summer hydroclimate from stable isotopes in Iberian trees

Tree rings are natural archives that annually record distinct types of past climate variability depending on the parameters measured. Here, we use ring-width and stable isotopes in cellulose of trees from the northwestern Iberian Peninsula (IP) to understand regional summer hydroclimate over the last 400 years and the associated atmospheric patterns. Correlations between tree rings and climate data demonstrate that isotope signatures in the targeted Iberian pine forests are very sensitive to water availability during the summer period, and are mainly controlled by stomatal conductance. Non-linear methods based on extreme events analysis allow for capturing distinct seasonal climatic variability recorded by tree-ring parameters and asymmetric signals of the associated atmospheric features. Moreover, years with extreme high (low) values in the tree-ring records were characterised by coherent large-scale atmospheric circulation patterns with reduced (enhanced) moisture transport onto the northwestern IP. These analyses of extremes revealed that high/low proxy values do not necessarily correspond to mirror images in the atmospheric anomaly patterns, suggesting different drivers of these patterns and the corresponding signature recorded in the proxies. Regional hydroclimate features across the broader IP and western Europe during extreme wet/dry summers detected by the northwestern IP trees compare favourably to independent multicentury sea level pressure and drought reconstructions for Europe. Historical records also validate our findings that attribute non-linear moisture signals recorded by extreme tree-ring values to distinct large-scale atmospheric patterns and allow for 400-year reconstructions of the frequency of occurrence of extreme conditions in late spring and summer hydroclimate.

Continued obliquity pacing of East Asian summer precipitation after the mid-Pleistocene transition

Records from natural archives show that the strength of the East Asian summer monsoon (EASM) strongly depends on the orbital configuration of the Earth. However, the dominant orbital cycles driving EASM have been found to be spatially different. Speleothem stable oxygen isotopic records from southern China, which are believed to reflect large-scale changes in the Asian monsoon system, are dominated by climatic precession cycles. Further north, on the Chinese Loess Plateau (CLP), loess-and-paleosol sequences, which are argued to be controlled by monsoon intensity, are in pace with global ice volume changes dominated by obliquity, and after the mid-Pleistocene transition by 100-kyr cycles. To understand these critical discrepancies, here we apply a novel proxy based on the trace metal compositions of pedogenic carbonate in the eolian deposits on the CLP to reconstruct summer precipitation over the last 1.5 million years. Our reconstructions show that summer precipitation on the CLP is dominantly forced by obliquity not in pace with the ice-volume-imprinted loess-paleosol sequences before and after the mid-Pleistocene transition or with the precession-paced speleothem oxygen isotopic records. Coupled with climate model results, we suggest that the obliquity-driven variations of summer precipitation may originate from the gradient of boreal insolation that modulates the thermal contrast between the Asian continent and surrounding oceans.

Mysterious and Mortiferous Clouds: The Climate Cooling and Disease Burden of Late Antiquity

AbstractWhat influence did climate have on disease in Late Antiquity? Natural archives of pre-instrumental temperature indicate significant summer cooling throughout the period. The coolest stretch spanned the 6th and 7th c., and corresponds startlingly to the appearance of the Justinianic Plague in the Mediterranean region. Drawing on principles from landscape epidemiology, this paper marries textual evidence for disease with palaeoclimatic data, in order to understand how gradual and dramatic climatic change, the 535–50 downturn especially, may have altered the pathogenic burden carried in Late Antiquity. Particular attention is paid to the Justinianic Plague, but the potential impacts of a changing climate on malaria and non-yersinial, non-plague, epidemics are not overlooked.

Dendroclimatology and historical climatology of Voronezh region, European Russia, since 1790s

ABSTRACTExisting high‐resolution reconstructions of hydroclimate variability in Europe are lacking natural proxy data from European Russia. For this reason, developing new hydroclimate proxies for this vast region is crucial. It is even more important, because drought evidences from the forest‐steppe region of European Russia will elucidate the eastern borders of large‐scale meteorological events that had been covering large parts of Europe in the past. In this study, we provide new tree‐ring chronologies of Pinus sylvestris L. for the site in the southernmost natural pine forest in European Russia. Based on these chronologies, we develop a quantitative drought reconstruction and disclose the driest years in the region since 1790s. The reconstruction of Standardized Precipitation Evapotranspiration Index explains 29–39% of instrumental period variability, it adequately tracks low‐frequency (30–50 years) variations of drought indices as well as extreme events. Collection of historical evidences from periodicals of the 19th century and other historical evidences helped to verify the new reconstruction. Using gridded precipitation reconstruction over Europe, we showed a possible existence of large‐scale hydroclimate events that had occurred in the East European forest‐steppe region in the 19th century. Possible connections of drought events in European Russia with Atlantic Multidecadal Oscillation and Scandinavian teleconnection pattern are discussed. We argue that being a complex natural archive, ring width of pine in Voronezh region can be successfully used as an estimator of prolonged droughts (1–2 years).