查看更多>>摘要：The quantitative assessment of glacier flow velocity dynamics plays a pivotal role in understanding its response mechanisms concerning climate warming.This work provides a systematic quantitative assessment of the deceleration status of glaciers in this region by investigating the motion evolution of typical glaciers in Mount Gongga in recent years,thereby revealing the seasonal dynamics and inter-annual evolution over an extensive time span.We used the optical flow-small baseline subset(OF-SBAS)method to compute the time-series velocities of the Hai-luogou Glacier and the Mozigou Glacier using 178 archived Sentinel-1 satellite synthetic aperture radar(SAR)images from 2014 to 2021.The findings revealed a prominent seasonal pattern in glacier motion,characterised by cyclic variations in velocity from cold to warm seasons.Moreover,we identified variations in velocities across distinct regions of the glacier surface,underscored by the lag in the peak time node of glacier flow with increasing elevation.This pattern may have been determined by a combination of internal and external factors,including mass accumulation and ablation-driven subglacial drainage,as well as the glacier geomorphological setting.Furthermore,during 2015-2021,the glaciers on the eastern slope of Mount Gongga exhibited an overarching trend of deceleration.Notably,the ablation area of the Hailuogou Glacier recorded the most substantial deceleration,exceeding 8％per year.This study underscores the efficacy of the OF-SBAS method in extracting long-term glacier velocities.This work also establishes a robust foundation for the analysis of spatiotemporal fluctuations in glacier movement within the context of climate warming.
查看更多>>摘要：Global warming is causing glaciers to retreat and glacial lakes to expand in the Himalayas,which amplifies the risk of glacial lake outburst debris flows(GLODFs)and poses a significant threat to downstream lives and infrastructures.However,the complex interplay between GLODF occurrences and associated indicators,coupled with the lack of a comprehensive susceptibility indicator system that considers the entire GLODF process,presents a substantial challenge in assessing GLODF susceptibility in the Himalayas.This study proposes a process-driven GLODF susceptibility assessment indicator system responding to climate change that considers the complete process of GLODF formation,incorporating relevant parameters about upstream,themselves,and downstream of glacial lakes.Furthermore,to mitigate subjective factors associated with traditional evaluation methods,we developed three novel hybrid machine-learning models by integrating classic machine-learning algorithms with the whale optimization algorithm(WOA)to delineate the distribution of GLODF susceptibility in the Himalayas.All the hybrid models effectively predicted the GLODFs occurrence,with the WOA-SVC model demonstrating the highest prediction accuracy.Approximately 34％of the catchments exhibit high and very high susceptibility levels,primarily concentrated along the north and south sides of the Himalayan ridge,particularly in the eastern and central Himalayas.Indicators capturing the physical formation process of hazards,such as topographic potential(highest relative importance value of 40％),can precisely identify GLODF.A total of 128 catchments pose potential transboundary threats,with 24 classified as having a very high susceptibility level and 25 as having a high susceptibility level.Notably,the border region between China and Nepal is a prominent hotspot for transboundary threats of GLODF.These findings can provide valuable clues for disaster prevention,mitigation,and cross-border coordination in the Himalayas.
查看更多>>摘要：The sea level in coastal areas of China reached the second highest in 2021,just after that recorded in 2022.External force and dynamic analyses based on tide gauges,satellite observations,reanalysis data and regional numerical outputs were conducted to understand these abnormally high sea levels and determine their possible causes.Results show that the coastal sea level of China had increased at an annual rate of 3.4±0.3 mm during 1980-2021,with an acceleration of 0.06±0.02 mm per year2.The superposition of significant oscillations of quasi-2,3-7,quasi-9,quasi-11,quasi-19 and 20-30 years contributed to the anomalously high sea levels.The negative-phased El Niño/Southern Oscillation was correlated with the anomalously high sea level and the north-south anti-phase pattern of the coastal sea level in 2021.Meanwhile,phase lags of l-4 months occurred with the sea-level response.On a decadal timescale,the Pacific Decadal Oscillation(PDO)was negatively correlated with the anomalous mean sea level(MSL),and the negative-phased PDO contributed to the anomalous sea-level change in 2021.Particularly,the monthly MSL peaked in April and July,and the contribution of wind stress to the anomalously high sea level was 38.5％in the south of the Taiwan Strait in April and 30％along the coast of China in July.These results were consistent with the tide gauge and satellite data.Close agreement was also observed between the coastal sea-level fingerprint and the air and sea surface temperatures.
查看更多>>摘要：Near-surface wind speed exerts profound impacts on many environmental issues,while the long-term(≥60 years)trend and multidecadal variability in the wind speed and its underlying causes in global high-elevation and mountainous areas(e.g.,Tibetan Plateau)remain largely unknown.Here,by examining homogenized wind speed data from 104 meteorological stations over the Tibetan Plateau for 1961-2020 and ERA5 reanalysis datasets,we investigated the variability and long-term trend in the near-surface wind speed and revealed the role played by the westerly and Asian monsoon.The results show that the homogenized annual wind speed displays a decreasing trend(-0.091 m s-1 per decade,p＜0.05),with the strongest in spring(-0.131 m s-1 per decade,p＜0.05),and the weakest in autumn(-0.071 m s-1 per decade,p＜0.05).There is a distinct multidecadal variability of wind speed,which manifested in an prominent increase in 1961-1970,a sustained decrease in 1970-2002,and a consistent increase in 2002-2020.The observed decadal variations are likely linked to large-scale atmospheric circulation,and the correlation analysis unveiled a more important role of westerly and East Asian winter monsoon in modulating near-surface wind changes over the Tibetan Plateau.The potential physical processes associated with westerly and Asian monsoon changes are in concordance with wind speed change,in terms of overall weakened horizontal air flow(i.e.,geostrophic wind speed),declined vertical thermal and dynamic momentum transfer(i.e.,atmospheric stratification thermal instability and vertical wind shear),and varied Tibetan Plateau vortices.This indicates that to varying degrees these processes may have contributed to the changes in near-surface wind speed over the Tibetan Plateau.This study has implications for wind power production and soil wind erosion prevention in the Tibetan Plateau.
查看更多>>摘要：To address data scarcity on long-term glacial discharge and inadequacies in simulating and predicting hydrological processes in the Tien Shan,this study analysed the observed discharge at multiple timescales over 1980s-2017 and projected changes within a representative gla-cierized high-mountain region:eastern Tien Shan,Central Asia.Hydrological processes were simulated to predict changes under four future scenarios(SSP1,SSP2,SSP3,and SSP5)using a classical hydrological model coupled with a glacier dynamics module.Discharge rates at annual,monthly(June,July,August)and daily timescales were obtained from two hydrological gauges:Urumqi Glacier No.l hydrological station(UGH)and Zongkong station(ZK).Overall,annual and summer discharge increased significantly(p＜0.05)at both stations over the study period.Their intra-annual variations mainly resulted from differences in their recharge mechanisms.The simulations show that a tipping point in annual discharge at UGH may occur between 2018 and 2024 under the four SSPs scenarios.Glacial discharge is predicted to cease earlier at ZK than at UGH.This relates to glacier type and size,suggesting basins with heavily developed small glaciers will reach peak discharge sooner,resulting in an earlier freshwater supply challenge.These findings serve as a reference for research into glacial runoff in Central Asia and provide a decision-making basis for planning local water-resource projects.
查看更多>>摘要：The increasingly frequent and severe regional-scale compound heatwave-drought extreme events(CHDEs),driven by global warming,present formidable challenges to ecosystems,residential livelihoods,and economic conditions.However,uncertainty persists regarding the future trend of CHDEs and their insights into regional spatiotemporal heterogeneity.By integrating daily meteorological data from observations in 1961-2022 and global climate models(GCMs)based on the Shared Socioeconomic Pathways,the evolution patterns of CHDEs were compared and examined among three sub-catchments of the Yangtze River Basin,and the return periods of CHDE in 2050s and 2100s were projected.The findings indicate that the climate during the 2022 CHDE period was the warmest and driest recorded in 1961-2022,with precipitation less than 154.5 mm and a mean daily maximum temperature 3.4 ℃ higher than the average of 1981-2010,whereas the char-acteristics in the sub-catchments exhibited temporal and spatial variation.In July-August 2022,the most notable feature of CHDE was its extremeness since 1961,with return periods of～200-year in upstream,80-year in midstream,and 40-year in downstream,respectively.By 2050,the return periods witnessed 2022 CHDE would likely be reduced by one-third.Looking towards 2100,under the highest emission scenario of SSP585,it was projected to substantially increase the frequency of CHDEs,with return periods reduced to one-third in the upstream and downstream,as well as halved in the midstream.These findings provide valuable insights into the changing risks associated with forthcoming climate extremes,emphasizing the urgency of addressing these challenges in regional management and sustainable development.
查看更多>>摘要：Due to concerns about carbon leakage and sectoral competitiveness,the European Union(EU)proposed implementing the carbon border adjustment mechanism(CBAM).The effectiveness and potential negative consequences of CBAM have aroused extensive discussion.From the perspective of the economy-wide analysis,this study uses a global computable general equilibrium model to explore the rationality of CBAM from the aspects of socioeconomic impact and the effects of promoting climate mitigation.Furthermore,the potential alternative mechanism of CBAM is proposed.The results show that CBAM can reduce the EU's gross domestic product(GDP)loss;however,the GDP loss in all other regions increases.Moreover,CBAM raises household welfare losses in most regions,including the EU.Second,although CBAM can reduce the marginal abatement cost in eight regions,it comes at the cost of greater economic losses.Furthermore,the economic and household welfare cost of raising emissions reduction targets in regions like the USA and Japan is substantially higher than the impact of passively accepting the CBAM;therefore,CBAM's ability to drive ambitious emission reduction initiatives may be limited.Finally,for the potential alternative mechanism,from the perspective of reducing economic cost and household welfare losses,the EU could implement domestic tax cuts in the short-term and promote global unified carbon pricing in the long-term.
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