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This paper revealed a physical connection between the antiphase variation in the preceding autumn Tibetan Plateau (TP) and Lake Baikal snow cover anomalies (TBSA) and the following winter North Atlantic Oscillation (NAO) on interannual time scales during 1979–2021. The antiphase variation in TBSA, accounting for 44% of the total years, has a dipole structure in autumn, which prolonged into the following winter. The persistent antiphase TBSA associated diabatic forcing, disturbances and transient eddies favor a double wave train structure spanning the TP (east of Baikal) and North Atlantic from autumn to winter. Amid the wave train, the circulation anomalies over the North Atlantic extract more energy from the basic flow due to the seasonal increase in the westerly jet, which further evolves into the winter NAO pattern. Our results provide new insights into the formation and projection of winter NAO from the perspective of subtropical and extratropical Eurasia snow. Plain Language Summary: A robust link exists in the preceding autumn antiphase Tibetan Plateau (TP) and Lake Baikal snow cover anomalies (TBSA) and the winter North Atlantic Oscillation (NAO) during 1979–2021. There are 44% years of antiphase variation in TBSA in autumn, which shows a dipole structure with one positive center over the TP and another negative center over the Baikal. Larger (smaller) snow cover over the TP (Baikal) stimulates a local low (high) pressure system via diabatic cooling (heating). Due to the jet waveguide effect, the antiphase TBSA associated diabatic forcing and perturbation along the subtropical westerly jet favor the atmospheric wave train spanning the TP and North Atlantic. The antiphase TBSA associated transient eddies along the extratropical belt contribute to the atmospheric wave train lying between the eastern Baikal and the North Atlantic owing to the eddy‐flow interaction. Along with the seasonal increase in the subtropical westerly jet from autumn to winter, the geopotential height anomalies in the double wave train associated with the antiphase TBSA gradually develop into the winter large‐scale NAO circulation through more energy extraction from the stronger basic flow. Key Points: A robust link of winter North Atlantic Oscillation (NAO) to the preceding fall antiphase Tibetan Plateau‐Baikal snow cover anomalies (TBSA)The antiphase TBSA associated diabatic forcing, disturbances and transient eddies favor a double wave train structure around 30°N and 60°NMore energy extracts over the North Atlantic due to the seasonal increase in the westerly jet, favoring the development of the winter NAO [ABSTRACT FROM AUTHOR]

This paper compares surface signatures of the zonally symmetric and asymmetric modes of stratospheric variability, which describe the strength of the polar vortex and a planetary wave‐1 pattern, respectively. Unlike a weak polar vortex followed by negative Arctic Oscillation–like anomalies, strong stratospheric wave activity features a polar vortex displacement with a deep planetary wave‐1 structure, resulting in positive North Atlantic Oscillation–like North American cooling in about 10 days. Moreover, the linkage between the stratosphere and surface is examined in two reanalyzes and four models of different configurations, which show more robust North American cooling following the displacement of the polar vortex due to strong stratospheric wave activity than the zonally symmetric weakening of the polar vortex. This suggests strong stratospheric wave activity acts as a better predictor for cold spells in the northern U.S. and Canada compared with a weak polar vortex. Plain Language Summary: A weak polar vortex in the winter stratosphere is likely associated with cold spells at the surface, yet there are large uncertainties in predicting surface cold events based on stratospheric signals. This study introduces a new method to separate stratospheric variability into the leading modes of zonally symmetric and asymmetric circulations. The zonally symmetric mode describes the strength of the polar vortex. A weak polar vortex is followed by cooling over northern Eurasia and midlatitude North America. In contrast, the zonally asymmetric mode characterizes a displacement of the polar vortex or a planetary wave‐1 pattern, with the positive phase featuring a high anomaly over North America and a low anomaly over Eurasia. This stratospheric wave pattern extends down to the surface, resulting in North American cooling and Eurasian warming in about 10 days. While both stratospheric modes are associated with surface cooling over North America, the linkage is more robust for the displacement than the zonally symmetric weakening of the polar vortex, based on analyses of several reanalyzes and models. This indicates that strong stratospheric wave activity serves as a better predictor for cold air outbreaks in the northern U.S. and Canada than the commonly used weak polar vortex events. Key Points: Distinct North American cooling signatures follow zonally symmetric and asymmetric modes of the stratosphereStrong stratospheric wave activity precedes positive North Atlantic Oscillation like North American coolingThe linkage between the stratospheric wave activity and the surface is robust in reanalyzes and models [ABSTRACT FROM AUTHOR]

This study investigates how El Niño‐Southern Oscillation (ENSO) modulates winter cold anomalies over central Eurasia (CE) using reanalysis data during 1950–2019. It is found that ENSO can significantly influence winter air temperature over CE mainly through modulating the strength and location of the cyclonic anomaly of Ural blocking (UB) or long‐lived UB events. A strong (weak) cyclonic anomaly of UB on the southeastern (eastern) side of the Ural Mountains tends to occur over midlatitude (high‐latitude) Eurasia during La Niña (El Niño) winters. Such anomalous circulation leads to a strong (weak) cold anomaly over CE, especially over East Asia, due to enhanced (weakened) cold air advection toward the CE during La Niña (El Niño). The UB‐related cyclonic anomaly in the midlatitude (high latitude) side of Eurasia is shown to be related to weakened (enhanced) eastward extension of strong westerly winds over midlatitude Eurasia during La Niña (El Niño) winters. Plain Language Summary: Observations show that in recent decades a strong cold anomaly appears over Eurasia, especially over central Eurasia (CE). This cold anomaly shows notable variations on interannual, decadal and interdecadal timescales. However, what factors lead to its interannual variations is not well understood. Here we show that El Niño‐Southern Oscillation (ENSO) events can influence Eurasian winter air temperature by modulating the strength and location of the cyclonic anomaly of Ural blocking (UB) or the frequency of long‐lived UB events. A La Niña (El Niño) favors a strong (weak) cyclonic anomaly circulation located in the southeastern (eastern) side of the Ural Mountains in the midlatitudes (high latitudes), which leads to a strong (weak) cold anomaly over CE especially in the low latitude Eurasia (i.e., East Asia) through enhanced (weakened) cold air advection. These new results help us understand the physical cause of the interannual variability of the Eurasian cold anomaly modulated by ENSO. Key Points: This paper examines the causal relationship between the Ural blocking (UB) and Eurasian cold anomaly during the La Niña phase in winterEl Niño‐Southern Oscillation plays an important role in the interannual variability of winter cold anomaly over the EurasiaThe UB leads to stronger cold anomaly over the Eurasian during the La Niña than El Niño [ABSTRACT FROM AUTHOR]

Oroclines are map‐view deformation of Earth's crust resulting from bending of quasi‐linear elements. The Central Asian Orogenic Belt (CAOB) is one of the largest and long‐lived accretionary orogens in the world and mainly consists of the Kazakhstan and Tuva–Mongolian oroclines. However, the mechanism of the oroclines is still in debate. Therefore, in this paper, we combine some investigation of high bathymetric relief resistance to subduction, review oroclinal bending models of the Kazakhstan Orocline, and propose a tentative model that involves asymmetric rollback in response to seamounts subduction and accretion, followed by bending associated with the convergence of the Siberian and Tarim cratons. Moreover, the role of pinning due to seamount and ridge subduction is probably more important than the convergence of continents in the CAOB. This model is compatible with the occurrence of seamounts, the spatial migration of intra‐oceanic arcs, and the development of multiple rollback processes during amalgamation of Eurasia. However, only geochemical and geochronological data will enable definition of the seamounts in CAOB so far, without much matching structural data. So we need more work to understand seamounts subduction and accretion as well as orocline bending in CAOB. [ABSTRACT FROM AUTHOR]

Aim: Previous analyses of remotely sensed data detected the multimodality of the tree‐cover distribution of the boreal forest, and identified areas with potentially alternative tree‐cover states. This paper aims at investigating the causes of multimodality and multistability of the boreal forest, their influence on the asymmetric tree species distribution between Eurasia and North America, and whether multistability could be associated with recent greening trends in leaf area index (LAI) and normalized difference vegetation index (NDVI). Location: Eurasian and North American boreal forests. Time period: 2000–2010. Major taxa studied: Boreal forest plant functional types. Methods: We employ a conceptual model based on tree species competition to simulate the sensitivity of tree cover to stochastic disturbances and to changes in environmental factors. We include different plant functional types based on survival adaptations, and force the model with remotely sensed environmental data. We analyse the model as a dynamical system. We use metrics from statistics and information theory to compare the detection of alternative tree‐cover states and greening trends in LAI and NDVI. Results: We find that multimodality and multistability can emerge through competition between different plant functional types. Additionally, our model is able to reproduce the asymmetry in tree species distribution between Eurasia and North America. Moreover, changes in permafrost distribution can be associated with phenomenological bifurcation points of the model. Finally, we find that the detection of multistable areas is not affected by recent vegetation trends, whereas shifts between alternative states could have affected the greening trends. Main conclusions: Tree‐cover multistability in the boreal region can emerge through competition between species subject to periodic disturbances. Changes in permafrost thaw and distribution could be responsible for the asymmetry in tree species distribution between North America and Eurasia. Climate change and permafrost degradation could cause shifts in tree‐cover states and dominant species. Recent vegetation greening trends in multistable areas could have been affected by shifts between alternative states. [ABSTRACT FROM AUTHOR]

The Bangong–Nujiang Suture Zone (BNSZ) is one of the main suture zones in the Tibetan Plateau and indicates the existence of the Bangong–Nujiang Neo‐Tethys Ocean (BNO). It was formed by the collision between the Qiangtang and Lhasa blocks after the closure of the BNO. However, its evolutionary processes and subduction polarity remain controversial. Research on the BNSZ is of great significance for exploring plate tectonic evolution and ocean–continent connection. The scarcity of the BNSZ structural data is one of the most important reasons for the debate of the BNO tectonic evolution. Based on structural analysis in the field and combined with previous petrology and palaeomagnetic data, this paper has determined that the closure time of the BNO is progressive and scissor‐like, from Middle Jurassic in the east to Early Cretaceous in the middle and late Early Cretaceous to early Late Cretaceous in the west. There was a three‐stage deformation in the BNSZ: (a) N–S‐directed compression induced by the initial collision; (b) WNW–directed transpression related to the stress adjustment; and (c) NE–SW‐directed compression caused by the low‐angle NE‐directed subduction of the Indus–Yarlung Zangbo Ocean. The different structural pattern along the eastern segment of the BNSZ may have resulted from orogenic bending due to the later Himalayan Orocline caused by the India–Eurasia collision in the Cenozoic. [ABSTRACT FROM AUTHOR]

Aim Climate change and loss of apex predators can affect ecosystem structure and function through modified limitation processes. We investigated, on a continental scale, whether mesopredator abundance is limited from the top down by large predators, as predicted by the mesopredator release hypothesis, or by bottom-up factors. The mesopredator in focus is the red fox Vulpes vulpes, a key predator in many ecosystems due to its strong effects on prey abundance. Location Europe and northern Asia. Methods Data on red fox density were compiled from published papers and reports. For each site, we collated presence-absence data on large carnivores ( Lynx lynx, Canis lupus, Canis aureus) and remote sensing data for factors potentially related to bottom-up limitation (winter severity, summer temperature, human density, primary productivity, tree cover). The data were analysed through structural equation modelling. Results The presence of lynx had a direct negative effect on red foxes, suppressing fox abundance. Also winter severity had a negative effect on red fox abundance, and in Eurasia as a whole this effect was partially mediated through lynx. Within the lynx distribution range, winter severity was the only bottom-up factor significantly affecting red fox abundance. Outside the lynx distribution range, primary productivity, summer temperature and human density had a positive effect on red fox abundance. Main conclusions Our results show that apex predators can limit mesopredator abundance on a continental scale, thus supporting the mesopredator release hypothesis. Winter severity also affected red fox abundance, partially due to an interaction between lynx and winter conditions. On the continental scale a complex network of processes operates with varying effects depending on mediation processes. Our results imply that apex predators can have an important effect on ecosystem structure by limiting mesopredator abundance, and we suggest that apex predators may dampen increases in mesopredator abundance driven by global warming. [ABSTRACT FROM AUTHOR]

Aim This paper reviews the available documentary, archaeological and palaeoecological evidence for the abandonment of agricultural land and consequent regeneration of the forest in Europe after the Black Death. Location Western and northern Europe. Methods This review is the result of an exhaustive search of the historical, archaeological and palaeoecological literature for evidence indicating agricultural decline and forest regeneration in Eurasia during the 14th century. The available evidence for landscape change can be divided into two categories: (1) documentary and archaeological sources, and (2) palaeoecological reconstructions of past vegetation. In the past few years, several pollen diagrams from north-west Europe have been reported with precise chronologies (decadal and even annual scale) showing the abandonment of farmland and consequent ecological change in the late medieval period. Results and main conclusions There is strong evidence of agricultural continuity at several sites in Western Europe at the time of the Black Death. The effects of the Black Death on the European rural landscape varied geographically, with major factors probably including the impact of the plague on the local population, and soil quality. At two sites in western and northern Ireland, the late medieval decline in cereal agriculture was probably a direct result of population reduction following the Black Death. In contrast, the decline in cereal production began at sites in Britain and France before the Black Death pandemic ofad 1347–52, and was probably due to the crisis in the agricultural economy, exacerbated by political instability and climate deterioration. Much of the abandoned arable land was probably exploited for grazing during the period between the decline in cereal farming and the Black Death. In the aftermath of the Black Death, grazing pressure was greatly reduced owing to reductions in the grazing animal population and a shortage of farmers. Vegetation succession on the abandoned grazing land resulted in increased cover of woody tree species, particularly Betula and Corylus, by the late 14th century. The cover of woodland was greatest at c.ad 1400, before forest clearance and agriculture increased in intensity. [ABSTRACT FROM AUTHOR]

This paper describes the forest gap model, FAREAST, its testing and its application to simulating the distribution, composition and dynamics of forests in eastern Eurasia. The FAREAST model is tested in north-eastern China, initially for forests on the elevational gradient of Changbai Mountain, which is located on the border of the People's Republic of China and the Democratic People's Republic of Korea. Subsequently, the model is inspected regionally for other northern Chinese mountains and, finally, it is applied to predict subcontinental forest communities in the Russian Far East. Boreal larch ( Larix spp.) forests cover much of the 6 million km2 of eastern Eurasia. Mixed broad-leaved tree species/Korean pine ( Pinus koraiensis) forests and spruce/fir ( Picea/ Abies) forests also occupy considerable areas. The model is tested using three types of information: (1) direct species composition comparisons between simulated and observed mature forests at the same locations; (2) forest type comparisons between simulated and observed forests along altitudinal gradients of several different mountains; and (3) comparison with forest stands in different succession stages of simulated forests. Model comparisons with independent data indicate that the FAREAST model is capable of representing many of the broad features of the forests of north-eastern China. After regional model validation in the north-eastern region of China, geographical model applications were developed for the forests of the Russian Far East. In simulations at 31 different sites distributed across the entire Russian Far East and including a wide variety of natural forests, the model demonstrates an ability to reproduce observed vegetation pattern. The model simulations are correct with respect to our criteria for 23 of the 31 sites, and there are close results for three other sites. Among the five sites that are incorrectly predicted, four simulations can be corrected by adding a simple assumption to the model for permafrost effects on water balance. Continental-scale forest cover can be simulated using a forest gap model to represent individual–plant interactions with one another, and their environment, and with parameters that describe the biology of each tree species. It appears that such a model, validated relatively locally (in this case, in north-eastern China), can then be applied over a much larger region. These results further imply that the Russian Far East forests can be regarded as a natural geographical expansion of north-eastern Chinese forests. In both regions, forests share not only similar species compositions, but also similar underlying causes of forest successional dynamics. [ABSTRACT FROM AUTHOR]

The main goal of this paper is to propose a new tool, in the form of Quantitative Bioclimatic Models (QnBMs), for reconstructing past climates based on fossil mammal associations. As a case study, European climatic conditions during the basal early Pleistocene will be inferred using QnBMs.The study uses faunas throughout the world to develop a quantitative bioclimatic model, which is then applied to Quaternary faunas from Eurasia.The models were constructed by applying multivariate linear regression to modern mammal faunas and climates from all over the world. The models were validated with a second group of modern faunas, which includes several from transitional zones between different climates (ecotones). To test the reliability of the method when applied to fossil associations, the results obtained for the Pleistocene have been compared with those obtained from palynology.Validation of the models shows that as many as 11 climatic factors can be inferred with high reliability using the regression models developed in this work. Comparisons of results in the late Pleistocene–Holocene of Barová (Czech Republic) between a palynological study and the quantitative bioclimatic analysis show a high degree of similarity. The results for the early Pleistocene show colder and drier climatic conditions for Europe than today.The application of the quantitative bioclimatic models to present day as well as Quaternary mammal faunas proves to be a useful tool for palaeoclimatic reconstruction during the Quaternary and probably most of the Neogene. Transfer functions are presented for a complete set of climatic factors, allowing a precise estimation of the climate in a locality from its mammal fauna. [ABSTRACT FROM AUTHOR]