Northwest Institute of Eco-Environment and Resources

Permafrost warming has the potential to amplify global climate change, because when frozen sediments thaw it unlocks soil organic carbon. Yet to date, no globally consistent assessment of permafrost temperature change has been compiled. Here we use a global data set of permafrost temperature time series from the Global Terrestrial Network for Permafrost to evaluate temperature change across permafrost regions for the period since the International Polar Year (2007-2009). During the reference decade between 2007 and 2016, ground temperature near the depth of zero annual amplitude in the continuous permafrost zone increased by 0.39 ± 0.15 °C. Over the same period, discontinuous permafrost warmed by 0.20 ± 0.10 °C. Permafrost in mountains warmed by 0.19 ± 0.05 °C and in Antarctica by 0.37 ± 0.10 °C. Globally, permafrost temperature increased by 0.29 ± 0.12 °C. The observed trend follows the Arctic amplification of air temperature increase in the Northern Hemisphere. In the discontinuous zone, however, ground warming occurred due to increased snow thickness while air temperature remained statistically unchanged.

Microplastics have recently been detected in the atmosphere of urban, suburban, and even remote areas far away from source regions of microplastics, suggesting the potential long-distance atmospheric transport for microplastics. There still exist questions regarding the occurrence, fate, transport, and effect of atmospheric microplastics. These questions arise due to limited physical analysis and understanding of atmospheric microplastic pollution in conjunction with a lack of standardized sampling and identification methods. This paper reviews the current status of knowledge on atmospheric microplastics, the methods for sample collection, analysis and detection. We review and compare the methods used in the previous studies and provide recommendations for atmospheric microplastic sampling and measurement. Furthermore, we summarize the findings related to atmospheric microplastic characteristics, including abundance, size, shapes, colours, and polymer types. Microplastics occur in the atmosphere from urban to remote areas, with an abundance/deposition spanning 1–3 orders of magnitude across different sites. Fibres and fragments are the most frequently reported shapes and the types of plastic which generally aligns with world plastic demand. We conclude that atmospheric microplastics require further research and greater understanding to identify its global distributions and potential exposure to human health through further field sampling and implementation of standardized analytical protocols.

Abstract The stability and resilience of the Earth system and human well-being are inseparably linked 1–3 , yet their interdependencies are generally under-recognized; consequently, they are often treated independently 4,5 . Here, we use modelling and literature assessment to quantify safe and just Earth system boundaries (ESBs) for climate, the biosphere, water and nutrient cycles, and aerosols at global and subglobal scales. We propose ESBs for maintaining the resilience and stability of the Earth system (safe ESBs) and minimizing exposure to significant harm to humans from Earth system change (a necessary but not sufficient condition for justice) 4 . The stricter of the safe or just boundaries sets the integrated safe and just ESB. Our findings show that justice considerations constrain the integrated ESBs more than safety considerations for climate and atmospheric aerosol loading. Seven of eight globally quantified safe and just ESBs and at least two regional safe and just ESBs in over half of global land area are already exceeded. We propose that our assessment provides a quantitative foundation for safeguarding the global commons for all people now and into the future.

Permafrost is a key element of the cryosphere and an essential climate variable in the Global Climate Observing System. There is no remote-sensing method available to reliably monitor the permafrost thermal state. To estimate permafrost distribution at a hemispheric scale, we employ an equilibrium state model for the temperature at the top of the permafrost (TTOP model) for the 2000–2016 period, driven by remotely-sensed land surface temperatures, down-scaled ERA-Interim climate reanalysis data, tundra wetness classes and landcover map from the ESA Landcover Climate Change Initiative (CCI) project. Subgrid variability of ground temperatures due to snow and landcover variability is represented in the model using subpixel statistics. The results are validated against borehole measurements and reviewed regionally. The accuracy of the modelled mean annual ground temperature (MAGT) at the top of the permafrost is ±2 °C when compared to permafrost borehole data. The modelled permafrost area (MAGT <0 °C) covers 13.9 × 106 km2 (ca. 15% of the exposed land area), which is within the range or slightly below the average of previous estimates. The sum of all pixels having isolated patches, sporadic, discontinuous or continuous permafrost (permafrost probability >0) is around 21 × 106 km2 (22% of exposed land area), which is approximately 2 × 106 km2 less than estimated previously. Detailed comparisons at a regional scale show that the model performs well in sparsely vegetated tundra regions and mountains, but is less accurate in densely vegetated boreal spruce and larch forests.

Abstract The Third Pole (TP) is experiencing rapid warming and is currently in its warmest period in the past 2,000 years. This paper reviews the latest development in multidisciplinary TP research associated with this warming. The rapid warming facilitates intense and broad glacier melt over most of the TP, although some glaciers in the northwest are advancing. By heating the atmosphere and reducing snow/ice albedo, aerosols also contribute to the glaciers melting. Glacier melt is accompanied by lake expansion and intensification of the water cycle over the TP. Precipitation has increased over the eastern and northwestern TP. Meanwhile, the TP is greening and most regions are experiencing advancing phenological trends, although over the southwest there is a spring phenological delay mainly in response to the recent decline in spring precipitation. Atmospheric and terrestrial thermal and dynamical processes over the TP affect the Asian monsoon at different scales. Recent evidence indicates substantial roles that mesoscale convective systems play in the TP’s precipitation as well as an association between soil moisture anomalies in the TP and the Indian monsoon. Moreover, an increase in geohazard events has been associated with recent environmental changes, some of which have had catastrophic consequences caused by glacial lake outbursts and landslides. Active debris flows are growing in both frequency of occurrences and spatial scale. Meanwhile, new types of disasters, such as the twin ice avalanches in Ali in 2016, are now appearing in the region. Adaptation and mitigation measures should be taken to help societies’ preparation for future environmental challenges. Some key issues for future TP studies are also discussed.

Abstract. The Tibetan Plateau (TP) has the largest areas of permafrost terrain in the mid- and low-latitude regions of the world. Some permafrost distribution maps have been compiled but, due to limited data sources, ambiguous criteria, inadequate validation, and deficiency of high-quality spatial data sets, there is high uncertainty in the mapping of the permafrost distribution on the TP. We generated a new permafrost map based on freezing and thawing indices from modified Moderate Resolution Imaging Spectroradiometer (MODIS) land surface temperatures (LSTs) and validated this map using various ground-based data sets. The soil thermal properties of five soil types across the TP were estimated according to an empirical equation and soil properties (moisture content and bulk density). The temperature at the top of permafrost (TTOP) model was applied to simulate the permafrost distribution. Permafrost, seasonally frozen ground, and unfrozen ground covered areas of 1.06 × 106 km2 (0.97–1.15 × 106 km2, 90 % confidence interval) (40 %), 1.46 × 106 (56 %), and 0.03 × 106 km2 (1 %), respectively, excluding glaciers and lakes. Ground-based observations of the permafrost distribution across the five investigated regions (IRs, located in the transition zones of the permafrost and seasonally frozen ground) and three highway transects (across the entire permafrost regions from north to south) were used to validate the model. Validation results showed that the kappa coefficient varied from 0.38 to 0.78 with a mean of 0.57 for the five IRs and 0.62 to 0.74 with a mean of 0.68 within the three transects. Compared with earlier studies, the TTOP modelling results show greater accuracy. The results provide more detailed information on the permafrost distribution and basic data for use in future research on the Tibetan Plateau permafrost.

In this study, individual precipitation samples, collected over 2 years at stations in different climatic regions of west China (Tibetan Plateau region, Tianshan region, and Altay) were analyzed for the stable isotopes of precipitation to improve our understanding of how vapor transport impacts the modern stable isotopic distribution. Our results identify regional patterns in both δ 18 O and deuterium excess (D excess, defined as δ D – 8 δ 18 O), and in particular we have identified the northward maximum extent of the southwest monsoon over the Tibetan Plateau. This demarcation is also the boundary for the fractionation effect of temperature on stable isotopes in precipitation. The patterns we have identified are as follows: (1) In the southern Tibetan Plateau, along the southern slope of the Himalayas, our results show a distinct seasonality for both δ 18 O and D excess as a result of the shift of summer monsoon moisture and winter westerly moisture transport. The signals of δ 18 O in the western Tibetan Plateau reveal that the region receives southwest monsoonal moisture. In the east of the plateau, stable isotopic variation shows alternation between monsoon intrusion and recycling of northern moisture. (2) In contrast, in Tianshan there is an apparent “temperature effect” in δ 18 O, with enriched values occurring in summer and depleted values occurring in winter. Seasonal D excess values, opposite to those observed in the southern Tibetan Plateau, are controlled by differing seasonal evaporation conditions. (3) In Altay, the most northern mountain region, the seasonal δ 18 O shows the same variation with that in Tianshan region. However, D excess shows no apparent seasonal variation.

Abstract Single‐atom catalysts (SACs) have attracted extensive interest to catalyze the oxygen reduction reaction (ORR) in fuel cells and metal–air batteries. However, the development of SACs with high selectivity and long‐term stability is a great challenge. In this work, carbon vacancy modified Fe–N–C SACs (Fe H –N–C) are practically designed and synthesized through microenvironment modulation, achieving high‐efficient utilization of active sites and optimization of electronic structures. The Fe H –N–C catalyst exhibits a half‐wave potential ( E 1/2 ) of 0.91 V and sufficient durability of 100 000 voltage cycles with 29 mV E 1/2 loss. Density functional theory (DFT) calculations confirm that the vacancies around metal–N 4 sites can reduce the adsorption free energy of OH*, and hinder the dissolution of metal center, significantly enhancing the ORR kinetics and stability. Accordingly, Fe H –N–C SACs presented a high‐power density and long‐term stability over 1200 h in rechargeable zinc–air batteries (ZABs). This work will not only guide for developing highly active and stable SACs through rational modulation of metal–N 4 sites, but also provide an insight into the optimization of the electronic structure to boost electrocatalytical performances.

Combustion-derived black carbon (BC) aerosols accelerate glacier melting in the Himalayas and in Tibet (the Third Pole (TP)), thereby limiting the sustainable freshwater supplies for billions of people. However, the sources of BC reaching the TP remain uncertain, hindering both process understanding and efficient mitigation. Here we present the source-diagnostic Δ(14)C/δ(13)C compositions of BC isolated from aerosol and snowpit samples in the TP. For the Himalayas, we found equal contributions from fossil fuel (46±11%) and biomass (54±11%) combustion, consistent with BC source fingerprints from the Indo-Gangetic Plain, whereas BC in the remote northern TP predominantly derives from fossil fuel combustion (66±16%), consistent with Chinese sources. The fossil fuel contributions to BC in the snowpits of the inner TP are lower (30±10%), implying contributions from internal Tibetan sources (for example, yak dung combustion). Constraints on BC sources facilitate improved modelling of climatic patterns, hydrological effects and provide guidance for effective mitigation actions.

The Tibetan Plateau and its surroundings are known as the Third Pole (TP). This region is noted for its high rates of glacier melt and the associated hydrological shifts that affect water supplies in Asia. Atmospheric pollutants contribute to climatic and cryospheric changes through their effects on solar radiation and the albedos of snow and ice surfaces; moreover, the behavior and fates within the cryosphere and environmental impacts of environmental pollutants are topics of increasing concern. In this review, we introduce a coordinated monitoring and research framework and network to link atmospheric pollution and cryospheric changes (APCC) within the TP region. We then provide an up-to-date summary of progress and achievements related to the APCC research framework, including aspects of atmospheric pollution's composition and concentration, spatial and temporal variations, trans-boundary transport pathways and mechanisms, and effects on the warming of atmosphere and changing in Indian monsoon, as well as melting of glacier and snow cover. We highlight that exogenous air pollutants can enter into the TP's environments and cause great impacts on regional climatic and environmental changes. At last, we propose future research priorities and map out an extended program at the global scale. The ongoing monitoring activities and research facilitate comprehensive studies of atmosphere-cryosphere interactions, represent one of China's key research expeditions to the TP and the polar regions and contribute to the global perspective of earth system science.

Drought is an intermittent disturbance of the water cycle that profoundly affects the terrestrial carbon cycle. However, the response of the coupled water and carbon cycles to drought and the underlying mechanisms remain unclear. Here we provide the first global synthesis of the drought effect on ecosystem water use efficiency (WUE = gross primary production (GPP)/evapotranspiration (ET)). Using two observational WUE datasets (i.e., eddy-covariance measurements at 95 sites (526 site-years) and global gridded diagnostic modelling based on existing observation and a data-adaptive machine learning approach), we find a contrasting response of WUE to drought between arid (WUE increases with drought) and semi-arid/sub-humid ecosystems (WUE decreases with drought), which is attributed to different sensitivities of ecosystem processes to changes in hydro-climatic conditions. WUE variability in arid ecosystems is primarily controlled by physical processes (i.e., evaporation), whereas WUE variability in semi-arid/sub-humid regions is mostly regulated by biological processes (i.e., assimilation). We also find that shifts in hydro-climatic conditions over years would intensify the drought effect on WUE. Our findings suggest that future drought events, when coupled with an increase in climate variability, will bring further threats to semi-arid/sub-humid ecosystems and potentially result in biome reorganization, starting with low-productivity and high water-sensitivity grassland.

Permafrost degradation may induce soil carbon (C) loss, critical for global C cycling, and be mediated by microbes. Despite larger C stored within the active layer of permafrost regions, which are more affected by warming, and the critical roles of Qinghai-Tibet Plateau in C cycling, most previous studies focused on the permafrost layer and in high-latitude areas. We demonstrate in situ that permafrost degradation alters the diversity and potentially decreases the stability of active layer microbial communities. These changes are associated with soil C loss and potentially a positive C feedback. This study provides insights into microbial-mediated mechanisms responsible for C loss within the active layer in degraded permafrost, aiding in the modeling of C emission under future scenarios.

Significance Conventional greenhouse gas mitigation policies ignore the role of global wetlands in emitting methane (CH 4 ) from feedbacks associated with changing climate. Here we investigate wetland feedbacks and whether, and to what degree, wetlands will exceed anthropogenic 21st century CH 4 emissions using an ensemble of climate projections and a biogeochemical methane model with dynamic wetland area and permafrost. Our results reveal an emerging contribution of global wetland CH 4 emissions due to processes mainly related to the sensitivity of methane emissions to temperature and changing global wetland area. We highlight that climate-change and wetland CH 4 feedbacks to radiative forcing are an important component of climate change and should be represented in policies aiming to mitigate global warming below 2°C.

<p indent="0mm">Qinghai-Tibet Plateau (QTP) is the largest high-altitude permafrost zone in the mid-latitudes. Due to the climate warming, permafrost degradation on the QTP has been widely recorded in the past decades. Since it greatly affects the East Asian monsoon, and even the global climate system, it is extremely important to understand permafrost current state, changes and its impacts. Based on literature reviews and some new data, this paper summarizes the characteristics of the current state permafrost on the QTP, including the active layer thickness (ALT), the spatial distribution of permafrost, permafrost temperature and thickness, as well as the ground ice and soil carbon storage in permafrost region. The new results showed that the permafrost and seasonally frozen ground area (excluding glaciers and lakes) is 1.06 million square kilometers and 1.45 million square kilometers on the QTP. The sub-stable, transitional, and unstable permafrost accounts for 30.4%, 22.1% and 22.6% of the total permafrost area. The permafrost thickness varies greatly among topography, with the maximum value in mountainous areas, which could be deeper than <sc>200 m,</sc> while the minimum value in the flat areas and mountain valleys, which could be less than <sc>60 m.</sc> The mean active layer thickness of the permafrost on the QTP is <sc>2.3 m,</sc> with 80% of the permafrost regions ranges from <sc>0.8 m</sc> to <sc>3.5 m.</sc> During 1980 to 2015, soil temperature at 0−10, 10−40, 40−100, <sc>100−200 cm</sc> increased at a rate of 0.439, 0.449, 0.396, and 0.259°C/<sc>10 a,</sc> respectively. From 2004 to 2018, the increasing rate of the soil temperature at the bottom of active layer was 0.486°C/<sc>10 a.</sc> These results show that the permafrost degradation has been accelerating. The permafrost degradation largely reduces the soil moisture. The ground ice volume of the permafrost is estimated up to <sc>1.27×10⁴ km³</sc> (liquid water equivalent). The soil organic carbon in the upper <sc>2 m</sc> of permafrost region is about 17 Pg; there is a large uncertainty in this estimation however due to the great heterogeneities in the soil column. Although the permafrost ecosystem is a carbon sink at the present, it is possible that it will shift to a carbon source due to the loss of soil organic carbon along with permafrost degradation. Overall, this paper shows that the plateau permafrost has undergone remarkable degradation during past decades, which are clearly proven by the increasing ALTs and ground temperature. Most of the permafrost on the QTP belongs to the unstable permafrost, meaning that permafrost over TPQ is very sensitive to climate warming. The permafrost interacts closely with water, soil, greenhouse gases emission and biosphere. Therefore, the permafrost degradation greatly affects the regional hydrology, ecology and even the global climate system. This paper also proposes approaches and methods to study the interactive mechanisms between permafrost and climate change, and the results can serve as a scientific basis for environmental protection, engineering design and construction in cold regions.

Abstract Desertification is the impoverishment of arid, semiarid, and some subhumid ecosystems. The assessment of global scale desertification vulnerability to climate change and human activity is important to help decision makers formulate the best strategies for land rehabilitation and combat global desertification in sensitive areas. There is no global desertification vulnerability map that considers both climate change and human activities. The main aim of this study was to construct a new index, the global desertification vulnerability index (GDVI), by combining climate change and human activity, provide another perspective on desertification vulnerability on a global scale, and project its future evolution. Using the probability density function of the GDVI, we classified desertification vulnerability into four classes: very high, high, medium, and low. The results of the analysis indicated that areas around deserts and barren land have a higher risk of desertification. Areas with a moderate, high, and very high desertification risk accounted for 13%, 7%, and 9% of the global area, respectively. Among the representative concentration pathways (RCPs), RCP8.5 projected that the area of moderate to very high desertification risk will increase by 23% by the end of this century. The areas where desertification risks are predicted to increase over time are mainly in Africa, North America, and the northern areas of China and India.

Black carbon (BC) has emerged as an important short-lived climate forcer. Due to its light absorption properties, BC can darken the snow/ice surface, affect the energy balance, and further lead to acceleration of the melting of the cryosphere (e.g., glaciers, snow cover, and sea ice). By reviewing the recent published literatures, we present an overview of the historical changes, spatial distribution of BC in snow/ice, and how these changes are related to the cryospheric melting. Ice core records show a rapid increase of BC concentrations that began in the 1850s and continued throughout the 20th century, which is consistent with an increase of BC emissions owing to industrialization. A decrease of BC amount since 1970s in Arctic and European ice cores has been partially attributed to the Clean Air Act. However, in the Himalayas, BC records show a continuous increase during this period. Generally, BC concentrations in snow and ice in the mid-latitude regions are one to two orders of magnitude higher than those in the polar regions. In particular, BC concentrations in aged snow and granular ice in the ablation areas of mountain glaciers are one to three orders of magnitude higher than those in fresh snow or snowpits in the glacier accumulation areas due to BC accumulation during melting season. BC in the surface snow/ice is responsible for about 20% of the albedo reduction in the Tibetan Plateau during glacier melt season. Globally, observations and modeling results indicate that radiative forcing (RF) induced by BC in snow and ice is highest in the mid-latitudes, ranging from several W m−2 in fresh snow to hundreds of W m−2 in aged snow and granular ice in the glacier ablation areas. The large BC-in-snow RF and associated snow albedo feedback lead to an acceleration in the total glacier melt (approximately 20%) and/or a reduction in the duration of the snow cover by several days, resulting in an increase of glacier discharge. Given our limited understanding of quantifying the role of BC in cryospheric melting, it is important to synthesize the existing research on the multi-scale processes related to BC in snow and ice to identify the gaps in our understanding of these processes and to propose a path forward to improve the quality of our observations of the aforementioned phenomena to fill these gaps.

The cryosphere is defined by the presence of frozen water in its many forms: glaciers, ice caps, ice sheets, snow, permafrost, and river and lake ice. In the extended Hindu Kush Himalaya (HKH) region, including the Pamirs, Tien Shan and Alatua, the cryosphere is a key freshwater resource, playing a vital and significant role in local and regional hydrology and ecology. Industry, agriculture, and hydroelectric power generation rely on timely and sufficient delivery of water in major river systems; changes in the cryospheric system may thus pose challenges for disaster risk reduction in the extended HKH region.

Abstract Permafrost on the Qinghai–Tibet Plateau (QTP) has undergone degradation as a result of recent climate change. This may alter the thermo‐hydrological processes and unlock soil organic carbon, and thereby affect local hydrological, ecological, and climatic systems. The relationships between permafrost and climate change have received extensive attention, and in this paper we review climate change for permafrost regions of the QTP over the past 30 years. We summarize the current state and changes in permafrost distribution and thickness, ground temperature, and ground ice conditions. We focus on changes in permafrost thermal state and in active‐layer thickness (ALT). Possible future changes in ground temperature and ALT are also discussed. Finally, we discuss the changes in hydrological processes and to ecosystems caused by permafrost degradation. Air temperature and ground temperature in the permafrost regions of the QTP have increased from 1980 to 2018, and the active layer has been thickening at a rate of 19.5 cm per decade. The response of permafrost to climate change is not as fast as in some reports, and permafrost degradation is slower than projected by models that do not account for conditions deep in permafrost.

Under a warming climate, degrading permafrost profoundly and extensively affects arctic and alpine ecology. However, most existing relevant studies are more focused on the hydrothermal impacts of vegetation on the underlying permafrost, or symbiosis between vegetation and permafrost, only very few on ecological impacts of permafrost degradation. Additionally, there are much more pertinent investigations in arctic and boreal regions than those in alpine and high-plateau regions at mid- and low latitudes. This study emphasizes on the impact mechanisms of permafrost degradation on vegetation both at high and mid-to low latitudes, addressing vegetation succession trajectories and associated changes in soil hydrology and soil nutrient above degrading permafrost. Permafrost degradation influences vegetation by altering soil hydrology, soil biogeochemical processes and microbial communities, which further improve soil nutrient availability. Furthermore, under a warming climate, vegetation may take two successional trajectories, towards a wetter or drier ecosystem within a certain time period, but to a drier ecosystem in the end upon the thaw of permafrost in case of permeable soils and good drainage. Thus, with rapidly developing remote-sensing and other space- and ground-based and air-borne observational networks and numerical predictive models, the impacting mechanisms of permafrost degradation on vegetation should be timely and better monitored, evaluated and modeled at desired spatiotemporal scales and resolutions by terrestrial or integrated ecosystem models.

Abstract. There is currently no glacial lake inventory data set for the entire high-mountain Asia (HMA) area. The definition and classification of glacial lakes remain controversial, presenting certain obstacles to extensive utilization of glacial lake inventory data. This study integrated glacier inventory data and 668 Landsat TM, ETM+, and OLI images and adopted manual visual interpretation to extract glacial lake boundaries within a 10 km buffer from glacier extent using ArcGIS and ENVI software, normalized difference water index maps, and Google Earth images. The theoretical and methodological basis for all processing steps including glacial lake definition and classification, lake boundary delineation, and uncertainty assessment is discussed comprehensively in the paper. Moreover, detailed information regarding the coding, location, perimeter and area, area error, type, time phase, source image information, and subregions of the located lakes is presented. It was established that 27 205 and 30 121 glacial lakes (size 0.0054–6.46 km2) in HMA covered a combined area of 1806.47±2.11 and 2080.12±2.28 km2 in 1990 and 2018, respectively. The data set is now available from the National Special Environment and Function of Observation and Research Stations Shared Service Platform (China): https://doi.org/10.12072/casnw.064.2019.db (Wang et al., 2019a).