Short-term Climatic Fluctuations Research Articles

Microbial and hydrothermal dolomite formation in Early Cretaceous lacustrine sediments in Yin'e Basin: Insights from petrology and geochemistry

Dolomite is widely present in geological history, but its origin has always been a prominent problem that troubles sedimentologists. For lacustrine dolomite, current research has not yet provided a reliable explanation for its complex genesis mechanism. The Early Cretaceous lakes in Northwest China host various morphological dolomites, providing valuable materials for exploring the origin of dolomites. According to their petrological and mineralogical characteristics, it can be divided into thick laminated dolomite, thin laminated dolomite, dolomitic mudstone, and vein dolomite. The ratios of trace elements and rare earth elements show that these dolomites precipitated in a brackish–suboxic environment. The high δ13C values (>8 ‰VPDB) of thick laminated dolomite and some thin laminated dolomite suggest the involvement of methane-producing microorganisms in the precipitation of dolomite, and the appearance of microscale/nanoscale spherical dolomite aggregates and the dispersed organic matter around dolomite particles jointly confirm that microbial-mediated biological activity promotes dolomite precipitation. The dolomite stoichiometry (mole % MgCO3) confirms that thick laminated dolomite was deposited in a restricted shallow water environment, while dolomitic mudstone is mainly deposited in relatively open water areas. The thin laminated dolomite in the shale laminae represents short-term or seasonal climatic and environmental fluctuations. In addition, some carbonate minerals of dolomitic mudstone in shallow water environment recrystallized by post-depositional hydrothermal effect, resulting in δ18O value decreased (<−10 ‰VPDB). The vein dolomite is characterized by high rare earth content and low δ13C and δ18O values, and its Sr isotope (0.712894 ± 0.000374) values reflect that the hydrothermal fluid may have been formed by the mixing of infiltrating lake water and crustal magmatic water. According to the characteristics of fluid inclusions, it is inferred that the hydrothermal fluid has the characteristics of low temperature (108.3 °C–159.8 °C), medium salinity (3.5 wt%–14.3 wt% NaCl) and high density (0.95–1.00 g/cm3). The microbial mediation and tectonic hydrothermal fluids play an important role in the formation of the Early Cretaceous lacustrine dolomite.

Short-Term Climatic Oscillations in the Central Region of the East-European Plain at the Beginning of the Holocene Based on Palynological Studies of Lacustrine Deposits

The Preboreal (11.75–10.70 ka BP) is still the least paleogeographically studied time interval in the central part of the East European Plain. High-resolution multi-proxy studies of lacustrine sediments at the Seltso site located in the Desna River floodplain (Dnieper River basin) were conducted. Radiocarbon dating, loss-on-ignition determination, sedimentological and palynological studies and identification of Non-Pollen Palynomorphs in lacustrine sediments allow us to reconstruct changes in vegetation caused by rapid warming at the Younger Dryas–Holocene boundary, short-term climatic fluctuations within the Preboreal and subsequent resumption of warming. Initial Preboreal warming reached its maximum at about 11.5 ka BP when a relatively dry continental climate existed. Between 11.4 and 11.2 ka BP, a short-term cooling corresponding to the Preboreal Oscillation in Greenland occurred, as indicated by a significant reduction of woody vegetation and expansion of open plant communities. In the Late Preboreal, approximately 11.2–10.7 ka BP, warming resumed, which was accompanied by a decrease in the climate continentality. Comparison with high-resolution lithological and palynological data from eight reliably dated sections of the central East European Plain indicates that in northwestern and central Europe, the impact of the Preboreal Oscillation cooling on the vegetation and the lake ecosystems’ development was probably somewhat stronger.

Thermodynamic and Dynamic Components of Winter Temperature Changes in Western Canada, 1950–2020

Abstract Most of the globe has experienced significant warming trends that have been attributed to anthropogenic climate change. However, these rates of warming are also influenced by short-term climate fluctuations driven by atmospheric circulation dynamics, resulting in inconsistent trend magnitudes in both time and space. This research evaluated winter (December–February) temperature trends over 1950–2020 at 91 climate stations across British Columbia (BC), Alberta (AB), and Saskatchewan (SK), Canada, and determined the components attributed to thermodynamic and dynamic (atmospheric circulation) factors. A synoptic climatological approach was used to classify atmospheric circulation patterns in the midtroposphere, relate those patterns to surface temperature, and evaluate changes in frequency. Moderate to high temperature increases over 71 years were found for most of the region, averaging 3.1°C in southern SK to 4.1°C in central-northern AB, and a maximum of 5.8°C in northern BC. Low to moderate increases were found for southern BC, averaging 1.2°C. Changes in atmospheric circulation accounted for 29% and 31% of observed temperature changes in central-northern BC and AB, respectively. Dynamic factors were a moderate driver in southern AB (18%) and central-northern SK (13%), and low in southern SK (5%). Negative dynamic contributions in southern BC (−6%), suggest that atmospheric circulation changes counteracted thermodynamically driven temperature changes. Results were consistent with trend analyses, indicating this method is well suited for trend detection and identification of thermodynamic and dynamic drivers. Results of this research improve our understanding of the magnitude of winter temperature changes critical for informing adaptation and climate-related policy decisions. Significance Statement Winter temperatures are strongly influenced by atmospheric circulation patterns, which move warm or cold air masses over large distances. We wanted to understand how changes in atmospheric circulation affect observed changes in winter temperatures in three provinces in western Canada. This also helps us to understand how much temperature change is due to anthropogenic (e.g., caused by greenhouse gases and land cover changes) and naturally occurring changes to Earth’s energy balance. Our results highlight the importance of understanding variability when selecting a time series for trend analyses or climate baselines for modeling studies. This study also helps to inform climate-related policies, decision-making, and adaptation strategies.

The Bølling-Allerød Transition in the Eastern Baltic: Environmental Responses to Climate Change.

This paper presents the results of a study on the Kulikovo section (south-eastern Baltic Sea coast), a sediment sequence exposing deposits of a post-glacial basin that existed along the edge of the glacier in the Late Pleistocene. The research was targeted at the reconstruction of the dynamics of the local environmental systems in response to climatic oscillations of the Lateglacial (the Older Dryas-first half of the Allerød). The evolution of the local biotic components on the territories of the Baltic region after the ice retreat is still poorly understood. Data from geochronological, lithological, diatom, algo-zoological and palynological analyses provide a reconstruction of local aquatic and terrestrial biocenoses and their response to short-term warmings and coolings that took place 14,000-13,400 cal yr BP. This study has demonstrated that, during the Older Dryas and first part of the Allerød (GI-1d and GI-1c), the aquatic and terrestrial environment of the Kulikovo basin underwent several changes, resulting in eight stages of the basin evolution, most probably related to the short-term climatic fluctuations that could have had a duration of several decades. The data obtained in this study have revealed the fairly dynamic and complex evolution of the pioneer landscapes, as indicated by the changes in the hydrological regime of the area and by the traced successions of plant communities from the pioneer swampy vegetation to park and real forests towards the middle of the Allerød.

Solar activity dominated the multidecadal- to centennial-scale humidity oscillations during the Little Ice Age in arid central Asia

Climatic instability has major impacts on water resources and catastrophic effects on fragile ecosystems in arid Central Asia (ACA). Short-term (decadal to centennial) climate fluctuations over the last millennium can help predict whether future climate instability and the frequency of extreme climate events will increase. Research has revealed higher moisture variability during the Little Ice Age (LIA) than during the Medieval Warm Period (MWP). However, the age control quality and temporal resolution of the proxy records that are used make it difficult to characterize the specific unstable climate fluctuations on decadal to centennial scales. Here, we present a well‐dated high‐resolution ostracod record from a remote alpine lake (Dalongchi Lake) in the central Tianshan Mountains, northwestern China, ACA, which has an average ∼ 3–4-year resolution and provides a record of inferred lake level fluctuations over the past millennium. The abundance of deep-water adapted Fabaeformiscandona gyirongensis was generally higher in the LIA and lower in the MWP and Current Warm Period (CWP), which confirmed the associations of warm–dry and cold–wet conditions in ACA. Notably, our ostracod records captured several distinct and dramatic secondary lake level fluctuations during the LIA. The abundance of F. gyirongensis peaked in four intervals at 1380–1460, 1540–1580, 1640–1720 and 1800–1940 CE, indicating sharp lake level increases, while the abundance decreased sharply in the three intervals of 1460–1540, 1580–1640 and 1720–1800 CE, indicating significant lake level decreases. There was a strong, inverse relationship between the lake level and the total solar irradiance (TSI) on the multidecadal to centennial scale, and the spectral analysis and wavelet coherence results suggest the presence of Gleissberg cycles. We propose that the century Gleissberg solar cycle directly affected regional humidity changes through temperature and evaporation forcing. Our findings suggest that solar activity probably plays an important role in determining future hydroclimatic changes in ACA.

Comparison of High-Resolution 14C and Luminescence-Based Chronologies of the MIS 2 Madaras Loess/Paleosol Sequence, Hungary: Implications for Chronological Studies

Numerous loess/paleosol sequences (LPS) in the Carpathian Basin span the period of Marine Isotope Stage (MIS) 2 and the last glacial maximum (LGM). Nevertheless, only two known records—Madaras and Dunaszekcső—preserve highly resolved records with absolute chronologies with minimal uncertainties, which enable the meaningful assessment of feedbacks and short-term climatic fluctuations over this period. The Madaras profile is located at the northern margin fringe of the Bácska loess plateau; Dunaszekcső, located on the Danube to its west, yields a chronology built on over 100 14C dates yet spans only part of MIS 2, missing half of the LGM including its peak. Here, we add to the previously published 14C chronology for Madaras (15 dates) with an additional 17 14C and luminescence ages. Resulting age models built solely on quartz OSL and feldspar pIRIRSL data underestimate the 14C based chronology, which is likely based on inaccuracies related to luminescence signal behavior; we observe age underestimations associated with unusual quartz behavior and significant signal loss, a phenomenon also observed in Serbian and Romanian loess, which may relate to non-sensitized grains from proximal sources. Our new chronology provides higher resolution than hitherto possible, yielding consistent 2 sigma uncertainties of ~150–200 years throughout the entire sequence. Our study indicates that the addition of further dates may not increase the chronological precision significantly. Additionally, the new age model is suitable for tackling centennial-scale changes. The mean sedimentation rate based on our new age-depth model (10.78 ± 2.34 years/cm) is the highest yet recorded in the Carpathian Basin for MIS 2. The resolution of our age model is higher than that for the Greenland NGRIP ice core record. The referred horizons in our profile are all characterized by a drop in accumulation and a higher sand input, the latter most likely deriving from nearby re-exposed sand dunes.

The calcareous nannofossil record of the uppermost Maastrichtian-lower Palaeocene in the Kırıkkale Basin, in the Central Anatolian Region (Turkey)

The Late Cretaceous–Early Paleogene (K–Pg) was a critical period of transition in geological time. This period encompassed short-term climatic fluctuations on a global scale, changes in ocean circulation, and sudden and large extinctions of marine and terrestrial organisms. In the study area, located in the mid to low latitudes, the Late Cretaceous and Early Paleogene were very tectonically active due to the positioning of the site close to the collision zone of two large continents. The impacts of the global K–Pg crisis can be observed in the study area. In this study, the calcareous nannofossil contents of late Maastrichtian–Danian sediments were studied, and the nannofossil biostratigraphy determined, from samples from the Samanlık and Dizilitaşlar Formations, deposited in the Kırıkkale Basin. From three stratigraphic sections, 26 nannofossil genera and 36 nannofossil species were identified from the Late Maastrichtian UC20aTP and UC20bTP biozones and the NP1 and NP2 biozones of the Danian. Additionally, it was determined that the K–Pg boundary was not continuous in the study area. In the Kırıkkale Basin, relatively low abundances of Micula decussate Vekshina, 1959 signals a diagenetic effect and stressful environment in the Late Maastrichtian, whereas the relatively low abundances of Thoracosphaera operculata Bramlette &amp; Martini, 1964, Braarudosphaera bigelowii (Gran &amp; Braarud, 1935) Deflandre, 1947 and Futyania petalosa (Ellis &amp; Lohmann, 1973) Varol, 1989 in the Danian assemblages indicate unstable environmental conditions and major environmental perturbations that reflect tectonic activity in the region. No nannofossils were encountered in those samples taken from turbiditic levels, which contained high proportions of sand.

Fluvial bedrock gorges as markers for Late-Quaternary tectonic and climatic forcing in the Southwestern Alps

Fluvial incision is one of the major erosive processes acting at Earth's surface and is highly sensitive to tectonic, isostatic and climatic variations. The aim of this study is to distinguish between the short-term climatic fluctuations versus the long-term tectonic forcing contribution to Late-Quaternary fluvial incision, to better understand its timing and driving mechanism(s). To achieve this goal, we measured in situ-produced 36Cl concentrations along several river-polished gorge walls in Jurassic limestones of the Southwestern Alps. We then compared our dating results to previously-dated river gorges from nearby catchments. This allows us to highlight three trends of distinct incision dynamics, and to discuss their relationships with climate and tectonics. Trend 1 shows the direct impact of a paraglacial crisis in the rivers connected to glaciated areas. Trend 2 suggests an incision wave propagating along the non-glaciated tributaries following enhanced incision in the main streams. Trend 3 displays steady and low incision rates in gorges disconnected from any fluvial response to glacier retreat. Trend 3 also seems to highlight the potential of resistant lithologies to isolate portions of the river network from post-glacial incision propagation. Our analysis shows that gorges connected to upstream glaciers exhibit a significant response of fluvial incision to climatic fluctuations, evidenced by high-amplitudes incision rate variations hindering the long-term tectonic signal. In contrast, incision rates inferred from disconnected gorges are in agreement with previously-estimated long-term denudation and rock-uplift rates in the area. Based on the latter, we can conclude that Late-Quaternary river incision in the Southwestern Alps is readjusting to both short-term climatic forcing and long-term tectonic forcing.

Sequence stratigraphy and microplankton palaeoenvironmental dynamics across the Jurassic–Cretaceous transition in the Canadian Arctic

ABSTRACTThe Jurassic to Cretaceous strata exposed in the Rollrock Section, Sverdrup Basin, Arctic Canada, represent one of the northernmost continuous outcrops spanning this poorly understood transition. The Oxfordian–Valanginian mudstones of the Rollrock Section were deposited in a shallow marine environment and, as such, provide the ideal lithology to investigate the response of high latitude dinoflagellate cyst populations to the frequent environmental perturbations of this time. Using a multivariate statistical approach, distinct palaeoecologically significant groups are identified and directly linked to time and palaeoenvironments, allowing for the reconstruction of underlying long term palaeoenvironmental trends. These palaeoenvironmental trends are identified to be driven by sequence stratigraphic cycles. For the first time, fourth order sequences are recorded from this pivotal period in the Sverdrup Basin and reveal an additional level of short term climatic events that complicate the identification of long term trends. The relationship existing between marine phytoplankton and climate is utilised to decipher the interplay of long-term and short-term climate fluctuations, distinguishing them from evolutionary trends. Two groups of dinoflagellate cysts, identified by process morphology, are recorded to act as environmental proxies. High percentages of proximochorate dinoflagellate cysts, such as Trichodinium erinaceoides, indicate more proximal, high energy, nutrient rich conditions and are dominant in fourth order transgressive systems tracts. High percentages of chorate dinoflagellate cysts, such as Oligosphaeridium complex, signify distal, low energy, nutrient depleted conditions and are dominant in fourth order highstand systems tracts.

Rare events in the Arctic

Twenty years ago, the Arctic was more resilient than now as sea ice was three times thicker than today. Heavier and more persistent sea ice provided a buffer against the influence of short-term climate fluctuations. Sea ice/atmospheric interactions now point to revisiting the concept of abrupt change. The recent decade has seen Arctic extreme events in climate and ecosystems including some events beyond previous records that imply increased future uncertaintly. While their numbers may increase, the distribution of the type, location, and timing of extreme events are less predictable. Recent processes include albedo shifts and increased sensitivity of sea ice to storms in marginal seas. Such new extremes include Greenland ice mass loss, sea ice as thin and mobile, coastal erosion, springtime snow loss, permafrost thaw, wildfires, and bottom to top ecosystem reorganizations, a consilience of impacts. One cause for such events is due to natural variability in a wavy tropospheric jet stream and polar vortex displacements, interacting with ongoing Arctic Amplification: temperature increases, sea ice loss, and permafrost thaw. This connecting hypothesis is validated by the variability of rare events matching interannual and spatial variability of weather. A proposed way forward for adaptation planning is through narrative/scenario approaches. Unless CO2 emissions are reduced, further multiple types of Arctic extremes are expected in the next decades with environmental and societal impacts spreading through the Arctic and beyond.

Holocene Palynology and Pollen-Based Palaeoclimate Reconstruction of Lake Erçek (Eastern Anatolia); Short-Term Climatic Fluctuations and their Relation with Global Palaeoclimatic Change; Results of Cores E1 and E10

Bu çalışma Erçek Gölü’nün (Doğu Anadolu, Türkiye) güney kesiminden alınan E1ve E10 sediment karotlarının palinolojik ve stratigrafik incelenmesini kapsamaktadır. Karot örnekleri farklı su derinliklerinden gravite karot örnekleyici kullanılarak alınmıştır. Karot örneklerinin litolojisi çoğunlukla laminalı ritmik sediman, masif ve tabakalı seviyeler ile E10 karotunda bulunan tefra seviyesi içermekte ve göl tabanının faylı oluşundan dolayı farklı zaman aralıklarını temsil etmektedir. Karot örneklerinin yaşlandırılması Van Gölü örneklerinin polen ve tefra seviyeleriyle korelasyonuna dayandırılarak belirlenmiştir. Palinolojik inceleme sonuçlarına göre, Erçek Gölü’nün, Grönlandiyen paleovejetasyonu Amaranthaceae familyası baskın halofitik vejetasyon ve yarı kurak paleoiklim koşulları ile temsil edilmektedir. Meghaliyen katı ise Poaceae familyası baskın step vejetasyonu ve antropojenik pollenlere göre artan insan etkisi ile karakterize edilmektedir. Erçek Gölü çevresinde Meghaliyen paleoiklimi Grönlandiyen’den daha nemlidir ve günümüze doğru gelindikçe maksimum yaprak döken Quercus yayılımı ile temsil edilmektedir.

Annual climatic fluctuations and short-term genetic variation in the eastern spadefoot toad

In addition to variations on the spatial scale, short- and long-term temporal variations, too, can impose intense selection on the overall genetic diversity and composition of a population. We hypothesized that the allelic composition in populations of the eastern spadefoot toad (Pelobates syriacus) would change among successive years in accordance with the short-term changes in environmental conditions. Surprisingly, the effect of short-term climate fluctuations on genetic composition have rarely been addressed in the literature, and to our knowledge the effect of annual climatic fluctuations have not been considered meaningful. Our findings show that climatic variation among successive years, primarily the amount of rainfall and rainy days, can significantly alter both microsatellite allelic composition and diversity. We suggest that environmental (i.e. fluctuating) selection is differential across the globe, and that its intensity is expected to be greatest in regions where short-term climatic conditions are least stable.

Every-other-day clutch-initiation synchrony as an adaptive response to egg cannibalism in Glaucous-winged Gulls (Larus glaucescens)

Sea surface temperatures (SST) in the Pacific Northwest of North America rose 1 °C during the last half of the twentieth century. Cannibalism, a behavior observed in diverse taxa, is often associated with low food supplies, which for marine animals can be precipitated by high SSTs. In an 8 year study, we found that in years of higher sea surface temperatures, Glaucous-winged Gulls (Larus glaucescens) breeding in a colony in Washington State, Salish Sea, USA, tended to exhibit higher rates of egg cannibalism by males, higher levels of every-other-day clutch-initiation synchrony by females, and longer egg-laying seasons than in years of lower SST. Clutch-initiation synchrony increased the odds that an egg survived cannibalism and may serve as an adaptive response to egg cannibalism. Short-term climate and resource fluctuations associated with El Niño Southern Oscillation (ENSO) events may select for behavioral plasticity in marine organisms, allowing long-lived individuals such as marine birds to switch between alternative life history tactics. The implications for long-term SST warming, however, remain unknown.

Glacier Retreat in Iceland Mapped from Space: Time Series Analysis of Geodata from 1941 to 2018

In recent decades, glaciers outside Greenland and Antarctica have shown increasingly rapid rates of mass loss and retreat of the ice front, which is associated with climatic and oceanic warming. Due to their maritime location, Icelandic glaciers are sensitive to short-term climate fluctuations and have shown rapid rates of retreat and mass loss over the last decade. In this study, historical maps (1941–1949) of the US Army Map Service (AMS series C762) and optical satellite imagery (Landsat 1, Landsat 5, Landsat 7, Landsat 8, and Sentinel-2) are used to study the Langjökull, Hofsjökull and Vatnajökull ice caps. By the help of the Normalized Difference Snow Index (NDSI), the glacier terminus fluctuations of the ice caps from 1973 to 2018 and the Equilibrium Line Altitude (ELA) from 1973 to 2018 are analyzed. The results are compared with climate data, especially with mean summer temperatures and winter precipitation. Due to the negative temperature gradient with increasing altitude, bivariate histograms are generated, showing the glaciated area per altitude zone and time, and providing a prediction of the future development until 2050 and beyond. The results indicate that Langjökull, Hofsjökull and Vatnajökull are retreating and advancing over the study period in correlation with the mean summer temperature, with a steady decrease over time being the clearest and most significant trend. The lower parts of the glaciers, thus, will probably disappear during the next decades. This behaviour is also evident by an exceptional increase of the ELA observed on all three glaciers, which leads to a reduction of the accumulation zone.

О ПРИЧИНАХ ПОТЕПЛЕНИЯ КЛИМАТА НА ОСНОВЕ ИЗУЧЕНИЯ ИСТОРИИ ЧЕТВЕРТИЧНЫХ ОЛЕДЕНЕНИЙ КАВКАЗА (НА ПРИМЕРЕ МЕЖДУРЕЧЬЯ ТЕРЕКА И АНДИЙСКОГО КОЙСУ)

The Greater Caucasus experienced repeated glaciation during the Quaternary (early, middle, upper Pleistocene, late Glacial, and late Holocene), which occurred under changing climatic conditions and differentiated tectonic movements. These glaciations, of course, are associated with changes in terrain, the formation of new deposits, transgressions and regressions of the Caspian Sea, changes in vegetation and soil types, so the problem of glaciation affects all earth Sciences to varying degrees. The study of Quaternary glaciation, especially Holocene glaciation, is currently relevant for understanding climate change. Against the background of significant climate fluctuations within the epochs of glaciation, there are smaller cooling phases that cause the temporary onset of glaciers. Short-term climate fluctuations are manifested in oscillations – minor fluctuations in the languages of glaciers. All this indicates that the climate undergoes significant changes in a short time, which are reflected in the morphosculpture of the terrain, the latest deposits and modern precipitation. Glaciation of the Greater Caucasus in the Prikazbeksky region reached its maximum in the middle Pleistocene,when glaciers went far into the Ossetian basin. All these traces have been preserved due to the lower capacity of the Chanty-Argun glacier and its fluvioglacial flow, which developed during the late Pleistocene epoch. Volcanic activity, especially active in the late Pliocene and continuing up to the present time, is associated with the late horn stage of development of the Caucasus. The formation of the Rukhs-Dzuar molass formation more than 2 km thick in the late Pleistocene in the Ossetian basin of the Tersky-Caspian flexure is associated with the activity of volcanoes in the Kazbek volcanic region. In the early Pleistocene, volcanic activity on the BC decreased significantly. The most intense outbreak of volcanism in the Kazbek and Elbrus volcanic regions occurred at the beginning of the late Pleistocene, which roughly coincided with the maximum phase of the late Pleistocene (Bezengian) glaciation. Then, in the second half of the late Pleistocene, volcanic activity was manifested on the mount Kazbek. The last outbreak of volcanic activity occurred in the Holocene no more than 2-3 thousand years ago. Fresh lavas are available on Elbrus, Kazbek, in the Terek valley near villages. Sioni and on the Kel volcanic plateau. Fumarolic activity still continues on Elbrus. Thus, in the Kazbek region, eruptions occurred from the late Pliocene to the late Holocene inclusive. Keywords: Pleistocene, Holocene, glaciation stages, nival-glacial processes, causes of glaciations, climate change, anthropogenic factors, natural factors, Earth degassing, magmatogenic degassing branch, seismotectonic degassing branch, greenhouse gases, newest geodynamics, volcanism, mud regimes, volcanism, methane hydrates, land degradation, water reclamation.

Less climatic resilience in the Arctic

Twenty years ago the Arctic system was more resilient than now as sea ice was three times thicker than today. Heavier and more persistent sea ice provided a buffer against the influence of short-term climate fluctuations. Such recent increases in sea ice/atmospheric interactions lead to revisiting the concept of abrupt change. The Arctic climate is stabilized by a negative radiative feedback, as increased temperatures of the surface and atmospheric lose more long wave energy. However, through new shifts in albedo feedback, open ocean areas are absorbing more of the incoming solar heat. Recent multi-year environmental extremes, potential albedo instabilities, and increased sensitivity of sea ice to storms in marginal seas, are overcoming negative radiative feedback, which point to passing impending climatic and ecosystem thresholds. Unless CO2 emissions are reduced, further Arctic extremes are expected in the next decades with environmental and societal impacts spreading through the Arctic and beyond.

SEASONAL AND LONG-TERM CHANGES OF VEGETATION INDEX OF ARABLE LANDS OF BRYANSK REGION (CENTRAL RUSSIA): REGULARITIES AND DYNAMICS FACTORS

There are a number of different factors that affect the sustainable development of agriculture. Efficient use of land and water resources, taking into account the threats that may arise due to climate change, as well as the dynamics of plant growth and development. Vegetation indices play an important role in monitoring vegetation variations. This article provides information on seasonal and long-term changes in the EVI (Enhanced Vegetation Index) of arable land in the Bryansk region. The purpose of the article is to discern the course of the seasonal dynamics of the index, the ranges of its variability, probable causes of differences between 2000-2018. In this article, physicochemical research methods were used to calculate the humus content, surface topography characteristics, and agricultural use features based on cartographic and stock materials, and the soil composition and density were determined through fieldwork. Summarized material on changes in EVI values for a snowless period as a whole and for individual filming intervals (18 per year) in 2000-2018 is presented. The mechanism of the influence of a variety of edaphic vegetation conditions on smoothing the differences in EVI over a series of years with different meteorological conditions has been described. The results of the analysis of the factors of the long-term dynamics are presented, the role of short-term climatic fluctuations, a progressive decrease in the amount of precipitation, and changes in the species composition of grain crops in the long-term dynamics of EVI are demonstrated.

Paleoenvironmental setting, mechanism and consequence of massive organic carbon burial in the Permian Junggar Basin, NW China

The Junggar Basin in northwestern China is a typical “walled” sedimentary basin that has a prolonged basin evolution history from the Paleozoic to Cenozoic and is rich in petroleum resources. Permian strata reach thousands of meters in thickness and have been intensively studied for their record of regional tectonics and paleoenvironments. They have also been exploited for oil and gas for the past several decades. In this paper, we summarize perspectives on tectonic evolution, stratigraphic framework, sedimentary environments, and the paleoclimate of the Permian Junggar Basin and the adjacent Turpan Basin. Further, we discuss the mechanism and consequences of massive organic carbon burial. Based on a compilation of published radiometric dating datasets, an updated chronostratigraphic framework was proposed for the Junggar Basin. This framework constrains the ages of two main petroleum source intervals, the Fengcheng Formation and the Lucaogou and equivalent formations, as Early Permian and Middle Permian, respectively. Although a global warming and drying trend was present throughout the Permian Period, the regional climate over the Junggar Basin was drier in Early Permian and more humid in the Middle-Late Permian with short-term climatic fluctuations. During the deposition of the two petroleum source intervals, dry and temperate climate prevailed and evaporative lacustrine environment dominated. Organic matter enrichment was promoted by stable salinity stratification and limited dilution by inorganic sediments, leading to one of the richest lacustrine source rock deposits in the world. The average organic carbon burial rates were 11.2 gC/m2/yr for the Lucaogou Formation and 3.5 gC/m2/yr for the Fengcheng Formation, lower than the average organic carbon burial rate in modern lakes. However, considering the large areas of global tectonic lakes in the Permian Period, organic carbon burial in lacustrine environments could act as a significant carbon sink and impact the global carbon cycle and climate evolution.

Changes in the Soil Cover under the Impact of Short-Term Climate Fluctuations

The climate of the 1950s–1990s in the center of the Russian Plain was characterized by the alternation of cool–wet and warm–dry periods, which is confirmed by hydrothermal coefficients. The studies in the south of the forest-steppe of the Central Russian Upland (Belgorod oblast) based on the geoinformation analysis of different-time soil maps have revealed regular changes in the boundaries of soil areas of automorphic chernozems (Chernozems) related to these intra-century climatic cycles. The transformed chernozems area was 125 790 ha (38.5%). In general, 61.5% (328 885 ha) of soil areas in the studied region remained unchanged. The response of the soil cover was indicated by behavior of carbonates and leaching. It has been revealed that with increase of hydrothermal coefficient by more than 0.2, the effervescence line in chernozems is oscillating, which results in a change in the taxonomic position of soils at the subtype level.

A review of the rise and fall of ancient desert runoff agriculture in the Negev Highlands - A model for the southern Levant deserts

The rise and fall of desert agriculture in the southern Levant has been debated among scholars for the last 200 years, in the chronological, the socio-political and the environmental context. Based on c. 31 OSL ages of sediments from agricultural terraces in various sites in the Negev Highlands, the main phase of ancient desert agriculture was dated to between the 3rd-4th centuries CE and the 10th-11th centuries CE (Avni et al., 2013). Within this longue durée process of agricultural activities, no significant environmental or climatic change was observed coinciding with the Byzantine- Islamic transition in the 7th century CE.Our research, which focused on the natural processes that influenced the rise and fall of the Negev desert agriculture, found that the agricultural installations were sustainable for at least 700 years and parts of these agricultural constructions are still in use today. This long period of usage is a clear indication of their robust design and their good adaptation to the desert environment, despite possible short-term climatic fluctuations. However, continuous flooding, gulling, soil erosion and siltation required constant maintenance of agricultural systems by the local farmers. In addition, the political and economic changes that followed the Byzantine-Islamic transition triggered a gradual decrease in the economic value of the products of desert agriculture, followed by a disruption of the social-political balance between local farmers and herders. These made the desert runoff agriculture less viable, leading to its final demise after the 10th century CE. Therefore, a direct link between the rise and fall of desert runoff agriculture and the claimed climatic changes in the southern Levant seems unlikely.