Search Results (36)

The Irtysh River Basin (IRB), a transboundary river basin spanning China, Kazakhstan, and Russia, has experienced significant vegetation changes driven by climate change and human activities. This study investigated the spatiotemporal dynamics of different types of vegetation in the IRB from 2001 to 2020 using the normalized difference vegetation index (NDVI) and quantified the contributions of driving forces to the evolution of vegetation. The results revealed that the end of the global warming hiatus in 2013 aggravated climate changes, leading to an abrupt shift in NDVI dynamics. This spatial shift was mainly reflected in grassland and farmland in the arid regions of northern Kazakhstan, where overall vegetation cover has improved in recent years. Precipitation and temperature were identified as the main drivers of spatial vegetation differentiation in the basin, with precipitation being more limiting in arid regions, while temperature affected non-arid regions at higher latitudes more strongly, and climate change had a greater positive effect on vegetation in non-arid regions than in arid regions. The relative contribution of climatic factors to vegetation changes decreased from 45.93% before the abrupt change to 42.65% after the abrupt change, while the contribution of other drivers, including human activities, increased from 54.07% to 57.35%. The combined effect of climate change and human activities was more significant than that of individual drivers, with human interventions such as environmental policies and ecological restoration projects having strongly contributed to the greening trend in recent years. This study highlights the need for zonal management strategies in the IRB, prioritizing sustainable forest management in non-arid zones and sustaining environmental protection projects in arid regions to support vegetation restoration and sustainable ecosystem management. Full article

This study analyzes the temporal patterns of rainfed cereal phenology extracted from the GIMMS NDVI3g dataset in the main cereal-growing regions under a Mediterranean climate in Spain, Portugal, France and Italy during the period 1982–2022. The series before and after the beginning of the 21st century were analyzed separately. Phenological parameters were extracted using the modified dynamic threshold method, and their trends were analyzed. Correlation analyses were performed to study the relationships among these parameters and to analyze the influence of hydroclimatic variables on the start (SOS) and end (EOS) of the growing season. Results showed a temporal reversal in phenological trends between both study periods, coinciding with the global warming hiatus. In the first period (1982–2002), SOS and EOS advanced (−7.5 and −3.1 days, respectively), and the length of growing season (LOS) increased. However, during the second stage (2003–2022), SOS and EOS were delayed (7.5 and 1.7 days, respectively), and LOS decreased. Similar dynamics were observed for the influence of the hydroclimatic variables on SOS and EOS, stronger in the first period and weaker in the second. This study provides valuable information on the phenological dynamics of rainfed cereals that may be useful for their management and planning in climate change scenarios. Full article

The Indo-Pacific, a vast biogeographic of Earth, is influenced by both the Indian and East Asian monsoons. Despite its geographical importance, this region has been less studied compared to East Asia and India. Here, we present speleothem records from southern Thailand that cover the last 1500 years, including a hiatus during the Little Ice Age, providing insights into the interactions among climate dynamics, human influences, and ecological responses to climate change. Notably, our records lack the characteristic cold and warm periods observed in other regions, such as the Dark Ages Cold Period and Medieval Warm Period, which may reflect the complexity of the tropical climate system or the region’s unique topography. The analysis reveals a link between ENSO multi-decadal variability and hydroclimate conditions in southern Thailand, as evidenced by speleothem δ¹⁸O. Furthermore, a comparison between speleothem δ¹³C and the Normalized Difference Vegetation Index (NDVI) indicates significant vegetation changes in the last three decades, corresponding with increased atmospheric CO₂ levels and expansion of agricultural land due to human activities during the Current Warm Period. Additionally, our study suggests that an abrupt increase in sea surface temperatures may enhance vegetation growth in the Indo-Pacific by influencing atmospheric circulation and increasing precipitation. Full article

Local geological and tectonic processes have been pivotal in shaping the diverse sedimentation patterns observed in Jordan, forming sub-basins characterized by elevated organic matter content (TOC). This study aims to characterize the Maastrichtian basin, focusing on sedimentation rates using calcareous nannofossils and understanding paleoecological and paleo-oceanic conditions. It offers insights into the paleoenvironmental factors impacting oil shale deposition in the late Maastrichtian–Paleocene period. It employs classical biostratigraphical, semi-quantitative, and statistical methodologies to achieve its objectives of age determination and paleoecological insights. A total of 116 smear slides from two sites were obtained: the first, consisting of WA-1 (23 samples), WA-2 (18 samples), and WA-3 (11 samples), and the second, with 60 samples. Notably, the sites exhibit varying topography. WA-1 and WA-2, situated at lower elevations, have the highest Total Organic Carbon (TOC) levels, while areas with higher elevations in section four are visually identified by a light color. The study revealed varying patterns of calcareous nannofossil richness in the two investigated sites. These patterns were instrumental in defining biozones, with the utilization of marker species such as Lithraphidites quadratus, Micula murus, Micula prinsii, and Cruciplacolithus tenuis. Chronologically, these sections were classified as Maastrichtian–Paleogene, encompassing the following biozones in sequential order: UC-20a, UC-20b, UC-20c, UC-20d, and NP-2. Furthermore, the study identified two hiatus intervals, observed in sections WA-1 and KAS-1. The absence of certain biozones in the analyzed sections suggests that these sections correspond to distinct geological blocks within the basin, underscoring the role of tectonic forces during the deposition period. The sedimentation rate initially commenced at low levels but gradually increased due to topographic alterations. Notably, the biozone UC-20c demonstrated a clear trend toward warming and enhanced nutrient availability. In this context, the abundance and diversity of species were associated with increased continental influx into the sub-basin, resulting in rising nutrient levels and the number of calcareous nannofossils. This study enhances the understanding of the local and global effects such as tectonic and climates of the continuity of basins by deciphering calcareous nannofossil patterns and their correlation with sedimentation factors. Full article

Gaining a deep understanding of how climate change affects the carbon cycle in dryland vegetation is of utmost importance, as it plays a pivotal role in shaping the overall carbon cycle in global ecosystems. It is currently not clear how plant communities at varying elevations in arid mountainous regions will respond to climate change in terms of their productivity. The aim of this study was to investigate the effect of climate change on vegetation productivity in different altitudinal vegetation belts of the Tianshan Mountains between 2000 and 2021, utilizing satellite-derived vegetation productivity and climate data. The findings suggest a notable increase in vegetation productivity across diverse altitudinal vegetation belts. The productivity of vegetation in the coniferous forest and alpine meadow belts displayed a notably higher interannual trend compared to other vegetation belts. Notably, an increase in vegetation productivity was accompanied by warming and drying. The productivity of altitudinal vegetation belts, however, appears to be resilient to current climate trends and was not significantly impacted by the severity of atmospheric drought. The trend of increased vegetation productivity was primarily driven by CO₂ fertilization. Our results highlight that the extent of climate change may need to reach a threshold to noticeably affect variations in vegetation productivity in arid mountainous. Full article

Freezing/thawing indices are important indicators of the dynamics of frozen ground on the Qinghai-Tibet Plateau (QTP), especially in areas with limited observations. Based on the numerical outputs of Community Land Surface Model version 4.5 (CLM4.5) from 1961 to 2010, this study compared the spatial and temporal variations between air freezing/thawing indices (2 m above the ground) and ground surface freezing/thawing indices in permafrost and seasonally frozen ground (SFG) across the QTP after presenting changes in frozen ground distribution in each decade in the context of warming and wetting. The results indicate that an area of 0.60 × 10⁶ km² of permafrost in the QTP degraded to SFG in the 1960s–2000s, and the primary shrinkage period occurred in the 2000s. The air freezing index (AFI) and ground freezing index (GFI) decreased dramatically at rates of 71.00 °C·d/decade and 34.33 °C·d/decade from 1961 to 2010, respectively. In contrast, the air thawing index (ATI) and ground thawing index (GTI) increased strikingly, with values of 48.13 °C·d/decade and 40.37 °C·d/decade in the past five decades, respectively. Permafrost showed more pronounced changes in freezing/thawing indices since the 1990s compared to SFG. The changes in thermal regimes in frozen ground showed close relations to air warming until the late 1990s, especially in 1998, when the QTP underwent the most progressive warming. However, a sharp increase in the annual precipitation from 1998 began to play a more controlling role in thermal degradation in frozen ground than the air warming in the 2000s. Meanwhile, the following vegetation expansion hiatus further promotes the thermal instability of frozen ground in this highly wet period. Full article

The global climate shows an obvious warming trend, and the impact on water resources is increasing. Abrupt temperature change and warming hiatus are two important states of temperature change. The quantitative impacts of temperature change and warming hiatus on surface runoff remain unclear. Based on the measured runoff data from 60 representative hydrological stations in China from 1956 to 2016 and the Water Balance Model developed by the Research Center for Climate Change (RCCC-WBC), this paper analyzes the quantitative impacts of abrupt temperature change and warming hiatus on surface runoff. The results showed that the effects of three types of abrupt temperature changes on runoff in different basins in China are significantly different. The effects of abrupt temperature changes and warming stagnation on runoff in northern China are greater than those in southern China, and the effects of abrupt temperature changes and warming stagnation on runoff in the upper, middle, and lower reaches of the same basin are also different. Before the abrupt change in temperature, the influence of temperature on the surface runoff was less than 9%, and the influence of temperature on the runoff in some southern areas was weaker, only affecting less than 3% of the runoff. When the temperature changes abruptly, the influence of air temperature on the surface runoff in a small part of the arid region is up to 30%. The abrupt change in mean maximum temperature has both positive and negative driving effects on runoff in China, and the negative driving effect is concentrated in the areas with abrupt warming, affecting about 8% of the runoff on average. The average influence of abrupt mean temperature change on runoff in China is about 10%, and the area with a large influence on runoff change is concentrated in the area north of 40° N. The abrupt change in temperature in the middle and lower reaches of the Yellow River Basin has a great influence on the runoff change, up to 13%. The maximum impact of abrupt mean minimum temperature on runoff is concentrated in Northeast China, ranging from 9% to 12%. During the period of temperature stagnation, air temperature and runoff showed an obvious reverse trend. During this period, the average negative influence of drastic changes in air temperature on runoff was about 15%, but precipitation and runoff still maintained a good consistency, which may be due to the effect of other influencing factors which offset the negative driving effect of air temperature. Full article

Abrupt temperature changes and warming hiatuses have a great impact on socioeconomic systems; however, their mechanisms remain unclear. In this study, the quantitative mechanisms of the responses of abrupt seasonal temperature changes and warming hiatuses in China to their influencing factors were analysed using the monthly mean temperature (Tav), mean minimum temperature (Tnav), and mean maximum temperature (Txav) from 622 meteorological stations in China covering 1951–2018, the CMIP6 model data, and data at large spatial scales, including Atlantic multidecadal oscillation (AMO) data. The results showed that the contributions of the influencing factors to the abrupt changes in Tav, Tnav, and Txav showed large spatial variability and peaked in the spring and summer and bottomed out in the autumn. The Pacific decadal oscillation (PDO) greatly impacted the abrupt temperature changes in Northeast China and North China at a contribution rate of approximately 12%, strongly influenced the abrupt temperature changes south of the Yangtze River, and markedly influenced the abrupt temperature changes in Northwest China. The AMO had a large impact on temperature in most regions of China in all seasons except for the summer. The MEI mainly affected the abrupt seasonal temperature changes in the region between 25° N and 35° N. The Arctic oscillation (AO) substantially impacted the warming hiatuses in Northeast China in the winter at a contribution rate of approximately 12%. These influencing factors contributed less to warming hiatuses than to abrupt temperature changes. Among the regional influencing factors, AP and WS greatly impacted warming hiatuses, more so than abrupt temperature changes, while relative humidity (RH) and solar radiation (SR) contributed little to warming hiatuses. Full article

Vegetation phenology is one of the most sensitive indicators to understanding terrestrial ecosystem status and change. However, few studies have been conducted to reveal vegetation phenology variation characteristics over the past two decades, especially under the background of the global warming hiatus since 1998. The agricultural pastoral ecotone of northern China (APENC) is an ideal place to analyze land surface phenology (LSP) variation. Therefore, the spatiotemporal patterns of LSP were quantitatively analyzed at regional, basin and pixel scales based on time-series MODIS NDVI data (2001–2021). Results showed that: (i) The start of the growing season (SOS) occurred in 105–141 Julian days, the end of the growing season (EOS) was between 257 and 281 Julian days and the length of the growing season (LOS) varied from 130 to 172 days. The later SOS was mainly distributed in croplands and typical grassland areas, while the early SOS was observed in forests and sandy vegetation coverage areas. The early EOS occurred in typical grasslands, and the later EOS was concentrated in the southeast boundary. The magnitude of the SOS and LOS fluctuation was less than EOS. (ii) The SOS and EOS exhibited overall insignificant advanced and delayed trends at a rate of −0.09 days·yr⁻¹ and 0.12 days·yr⁻¹, respectively, and the LOS displayed an insignificant extended trend at a rate of 0.26 days·yr⁻¹ at a regional scale. The trends of phenological metrics were consistent with the APENC in the Yellow River and Haihe River Basins. The shortened trend of LOS occurred due to the delayed SOS and advanced EOS in the Songliao River and Continental Basins. (iii) The SOS variation gradually changed from an advanced trend to a delayed trend from a southwest to northeast direction in cropland and grassland ecosystems, whereas an opposite trend was found for EOS. The LOS exhibited a significant extended trend due to the significant advanced and delayed trend of SOS and EOS at p < 0.01 in forest ecosystems. This work provides a critical reference for the vegetation phenology dynamic research of semi-arid and semi-humid regions. Full article

Monitoring land surface phenology plays a fundamental role in quantifying the impact of climate change on terrestrial ecosystems. Shifts in land surface spring phenology have become a hot spot in the field of global climate change research. While numerous studies have used satellite data to capture the interannual variation of the start of the growing season (SOS), the understanding of spatiotemporal performances of SOS needs to be enhanced. In this study, we retrieved the annual SOS from the Moderate Resolution Imaging Spectroradiometer (MODIS) two-band enhanced vegetation index (EVI2) time series in the conterminous United States from 2001 to 2021, and explored the spatial and temporal patterns of SOS and its trend characteristics in different land cover types. The performance of the satellite-derived SOS was evaluated using the USA National Phenology Network (USA-NPN) and Harvard Forest data. The results revealed that SOS exhibited a significantly delayed trend of 1.537 days/degree (p < 0.01) with increasing latitude. The timing of the satellite-derived SOS was significantly and positively correlated with the in-situ data. Despite the fact that the overall trends were not significant from 2001 to 2021, the SOS and its interannual variability exhibited a wide range of variation across land cover types. The earliest SOS occurred in urban and built-up land areas, while the latest occurred in cropland areas. In addition, mixed trends in SOS were observed in sporadic areas of different land cover types. Our results found that (1) warming hiatus slows the advance of land surface spring phenology across the conterminous United States under climate change, and (2) large-scale land surface spring phenology trends extraction should consider the potential effects of different land cover types. To improve our understanding of climate change, we need to continuously monitor and analyze the dynamics of the land surface spring phenology. Full article

A region in the tropical western Pacific is selected to study the notable change in temperature between the recent warming hiatus period and the post-hiatus period. In total, three probable factors, namely sea-surface temperature (SST), cloud vertical structure (CVS) and wind speed, which may account for the temperature change are found to exhibit noticeable differences between these two periods. A one-dimensional atmospheric radiative transfer model, incorporating convective adjustment and energy exchange with the ocean, is developed to simulate the diurnal pattern of temperature profile under the influence of the three probable factors in the two concerned periods. Virtual profiles of sea-surface temperature, cloud vertical structure and wind speed in both periods are developed from data available in the literature. Diurnal patterns of temperatures near the air–sea interface are computed with the proposed model over a sufficient number of days. The simulated temperatures under different combinations of factors, in either the hiatus or post-hiatus period, are statistically analyzed to gain insights about the separate and combined effects of these three factors on causing climate change. Full article

The effect of climate prevails on a diverse time scale from days to seasons and decades. Between 1993 and 2013, global warming appeared to have paused even though there was an increase in atmospheric greenhouse gases. The variations in oceanographic variables, like current speed and sea surface temperature (SST), under the influence of the global warming hiatus (1993–2013), have drawn the attention of the global research community. However, the magnitude of ocean current and SST characteristics oscillates and varies with their geographic locations. Consequently, investigating the spatio-temporal changing aspects of oceanographic parameters in the backdrop of climate change is essential, specifically in coastal regions along Kuroshio current (KC), where fisheries are predominant. This study analyzes the trend of ocean current and SST induced mainly during the global warming hiatus, before and till the recent time based on the daily ocean current data from 1993 to 2020 and SST between 1982 and 2020. The Kuroshio extent is delineated from its surrounding water masses using an aggregation of raster classification, stretching, equalization, and spatial filters such as edge detection, convolution, and Laplacian. Finally, on the extracted Kuroshio extent, analyses such as time series decomposition (additive) and statistical trend computation methods (Yue and Wang trend test and Theil–Sen’s slope estimator) were applied to dissect and investigate the situations. An interesting downward trend is observed in the KC between the East coast of Taiwan and Tokara Strait (Tau = −0.05, S = −2430, Sen’s slope = −5.19 × 10⁻⁵, and Z = −2.61), whereas an upward trend from Tokara Strait to Nagoya (Tau = 0.89, S = 4344, Sen’s slope = 8.4 × 10⁻⁵, and Z = 2.56). In contrast, a consistent increasing SST in trend is visualized in the southern and mid-KC sections but with varying magnitude. Full article

This article aims to reconstruct the invasion of the ear-shaped pond snail, Radix auricularia (Linnaeus, 1758), to Lake Baikal, East Siberia. This species is widely distributed in the Palaearctic and Northern America, and since the early 20th century has formed abundant and sustained populations in Lake Baikal. The data provided on the morphological and genetic variability of R. auricularia help to better describe and delineate the species. With an integrative approach involving morphological and molecular data, we improved the knowledge of the intraspecific variability of R. auricularia in the most important characteristics used for its determination. Molecular sequences of nuclear spacer fragment ITS-2 and mitochondrial gene fragment cyt–b were obtained from 32 individuals of Radix (including seven outgroup Radix species) collected from various parts of Lake Baikal and adjacent waterbodies and compared with sequences of 32 individuals of R. auricularia from different regions of the Palaearctic as well as with individuals determinated as R. intercisa from Lake Baikal, R. iturupica from the Kurile Islands, R. ussuriensis from the Khabarovsk region, R. narzykulovi from Tajikistan, and R. schubinae from the Amur region. Molecular genetic analyses revealed that all specimens collected from Lake Baikal belong to R. auricularia. There are no genetically distinct groups of snails that would correspond to two morphospecies previously recorded in Lake Baikal (e.g., R. auricularia s. str. and R. intercisa). Variability of the characteristics that are commonly used for species identification (shell morphology, mantle pigmentation, shape and position of the bursa copulatrix, length and position of the bursa duct, length ratio of preputium to penial sheath) were found in individuals analysed with molecular genetics to be broader than recognised in the current literature. Some shells of R. auricularia collected from Lake Baikal resemble shells of another lymnaeid species, R. balthica, and without molecular assessment can be confused with the latter. Geometric morphometric analysis of more than 250 shells revealed no observed hiatus between Baikalian and non-Baikalian R. auricularia. The probable stages and pathways of R. auricularia invasion to Lake Baikal’s ecosystem are outlined and discussed. Factors such as global climate warming and human activity stimulated and facilitated the ongoing dispersal of ear pond snails within Lake Baikal. Full article

Mass balance observations are beneficial for assessing climate change in different world regions. This study analyzed the glacier elevation change, ice flux divergence, and surface mass balance (SMB) in the West Kunlun Mountains (WKM) on the Tibetan Plateau using remote sensing data, including satellite altimetry, glacier surface velocity, and thickness fields. Seventeen local glaciers were examined in detail and showed varying surface elevation changes from −0.39 ± 0.11 to 0.83 ± 0.10 m/a. Overall, we obtained a reasonably rapid elevation trend of 0.21 ± 0.14 m/a. By combining the ice flux divergence and surface mass balance, the overall thickness change of the WKM glacier over time is almost zero, and the WKM glacier shows a positive mass balance of 0.21 ± 0.98 m/a. Moreover, the ice flux divergence is more significant on the ice tongue than in the flat region due to the more considerable gradient of surface velocity and thickness fields. We found that glacier heterogeneity dynamics were associated with a surging dynamic mechanism concentrated in the glacier tongue and were induced by inner terrain instabilities. The glacier surging causes a drastic drop in glacier elevation but does not cause a glacier mass gain or loss, and it has an enhanced effect on the ice flux divergence. Therefore, glacier surging is the main reason for the decline of the two glaciers monitored. In addition, the long-term meteorological data analysis found that, since 2000, the air temperature warming hiatus may have balanced the three glaciers, and significantly increasing precipitation variation may cause the glacier to thicken the most. Full article

Spring phenology is the most sensitive indicator of climate change and exploring its response to climate change has important implications for ecosystem processes in the study area. The temperature changes before and after the global warming hiatus may affect the spatiotemporal pattern of land surface phenology. In this paper, taking the China–DPRK (Democratic People’s Republic of Korea)–Russia cross-border region as an example, based on GIMMS NDVI data, the Polyfit-Maximum method was used to extract the start date of the vegetation growing season (SOS). The variation trend of SOS and its response to climate change were analyzed in the early (1982–1998) and late (1998–2015) periods of the warming hiatus. At the regional scale, the spatial distribution of the SOS in the China–DPRK–Russia (CDR) cross-border area presents an elevation gradient, which is earlier in high-elevation areas and later in low-elevation areas. The temporal and spatial trend of SOS is mainly correlated by daytime maximum temperature (Tmax). The significant increase in Tmax in the early period promoted the advance of SOS (0.47 days/year), and the decrease in Tmax in the later period caused the delay of SOS (0.51 days/year). While the main influencing factor of the SOS changes in the region in the early and late periods was Tmax, the response of the SOS changes in China, DPRK and Russia to climate change also changed with the dramatic temperature changes during the warming hiatus. The Chinese side is increasingly responding to Tmax, while the North Korean side is becoming less responsive to climatic factors, and precipitation and radiation on the Russian side are driving the advance of the SOS. Full article