Abstract Monthly mean sea ice motion vectors and monthly mean sea level pressure （SLP） for the period of 1979-2006 are investigated to understand the spatial and temporal changes of Arctic sea-ice drift. According t...Abstract Monthly mean sea ice motion vectors and monthly mean sea level pressure （SLP） for the period of 1979-2006 are investigated to understand the spatial and temporal changes of Arctic sea-ice drift. According to the distinct differences in monthly mean ice velocity field as well as in the distribution of SLP, there are four primary types in the Arctic Ocean： Beaufort Gyre＋Transpolar Drift, Anticyclonic Drift, Cyclonic Drift and Double Gyre Drift. These four types account for 81% of the total, and reveal distinct seasonal variations. The Cyclonic Drift with a large-scale anticlockwise ice motion pattern trends to prevail in summer while the Anticyclonic Drift with an opposite pattern trends to prevail in winter and spring. The prevailing seasons for the Beaufort Gyre＋Transpolar Drift are spring and autumn, while the Double Gyre Drift trends to prevail in winter, especially in Feb- ruary. The annual occurring times of the Anticyclonic Drift and the Cyclonic Drift are closely correlated with the yearly mean Arc- tic Oscillation （AO） index, with a correlation coefficient of -0.54 and 0.54 （both significant with the confident level of 99%）, re- spectively. When the AO index stays in a high positive （negative） condition, the sea-ice motion in the Arctic Ocean demonstrates a more anticlockwise （clockwise） drifting pattern as a whole. When the AO index stays in a neutral condition, the sea-ice motion becomes much more complicated and more transitional types trend to take place.展开更多
On the way of the '1990 International Trans-Antarctic Expedition', the first author of this paper, the Chinese member of the expedition, collected 104 snow samples in 25-cm surface snow along a 5986-km route o...On the way of the '1990 International Trans-Antarctic Expedition', the first author of this paper, the Chinese member of the expedition, collected 104 snow samples in 25-cm surface snow along a 5986-km route on Antarctic ice sheet from west to east. The geographical distribution of δD across the Antarctica by the longest route is obtained from stable isotope analysis for the first time. After discussing regional differences of physical geographic conditions, maritime-continental influence, altitudes and latitudes at sampling sites, the distribution of δD is considered to have a close relation to latitudes, but the topographic effect is prominent in some particular regions. The mean annual temperature at sampling site and its relationship with δD in surface snow covering Antarctica from west to east are discussed also. The δD-temperature gradient from the south end of Antarctic Peninsula to Vostok obtained in this paper is very close to that in Terre Adelie Land obtained by predecessors. The snow-drift may make an important contribution to the relatively high δD-temperature gradient from Vostok to Mirnyy.展开更多
Water temperature is a critical indicator and weathervane of aquatic ecosystems.However,the vast majority of rivers lack long-term continuous and complete water temperature datasets.In this study,ensemble models by co...Water temperature is a critical indicator and weathervane of aquatic ecosystems.However,the vast majority of rivers lack long-term continuous and complete water temperature datasets.In this study,ensemble models by combining NARX(nonlinear autoregressive network with exogenous inputs)and air2stream were used to reconstruct daily river water temperatures for 27 hydrological stations in the Odra River Basin,one of the largest river systems in Europe.For each hydrological station,both the NARX and air2stream models were calibrated and validated,and the better-performed model was selected to reconstruct daily river water temperatures from 1985 to 2022.The results showed that hybrid modeling by combining NARX and air2stream is promising for reconstructing daily river water temperatures.Based on the reconstructed dataset,annual and seasonal trends of water temperature and characteristics of river heatwaves were evaluated.The results indicated that annual river water temperatures showed a consistent warming trend over the past 40 years with an average warming rate of 0.315C/decade.Seasonal river water temperatures indicated that summer warms faster,followed by autumn and spring,and winter river water temperatures showed an insignificant warming trend.River heatwaves are increased in frequency,duration,and intensity in the Odra River Basin,and 6 out of 27 hydrological stations have river heatwaves categorized as‘severe’and‘extreme’,suggesting that mitigation measures are needed to reduce the impact of climate warming on aquatic systems.Moreover,results showed that air temperature is the major controller of river heatwaves,and river heatwaves tend to intensify with the warming of air temperatures.展开更多
The association between biodiversity and belowground biomass(BGB) remains a central debate in ecology.In this study, we compared the variations in species richness(SR) and BGB as well as their interaction in the top(0...The association between biodiversity and belowground biomass(BGB) remains a central debate in ecology.In this study, we compared the variations in species richness(SR) and BGB as well as their interaction in the top(0–20 cm), middle(20–50 cm) and deep(50–100 cm) soil depths among 8 grassland types(lowland meadow, temperate desert, temperate desert steppe, temperate steppe desert, temperate steppe, temperate meadow steppe, mountain meadow and alpine steppe) and along environmental gradients(elevation, energy condition(annual mean temperature(AMT) and potential evapotranspiration(PET)), and mean annual precipitation(MAP)) based on a 2011–2013 survey of 379 sites in Xinjiang, Northwest China.The SR and BGB varied among the grassland types.The alpine steppe had a medium level of SR but the highest BGB in the top soil depth, whereas the lowland meadow had the lowest SR but the highest BGB in the middle and deep soil depths.The SR and BGB in the different soil depths were tightly associated with elevation, MAP and energy condition;however, the particular forms of trends in SR and BGB depended on environmental factors and soil depths.The relationship between SR and BGB was unimodal in the top soil depth, but SR was positively related with BGB in the middle soil depth.Although elevation, MAP, energy condition and SR had significant effects on BGB, the variations in BGB in the top soil depth were mostly determined by elevation, and those in the middle and deep soil depths were mainly affected by energy condition.These findings highlight the importance of environmental factors in the regulations of SR and BGB as well as their interaction in the grasslands in Xinjiang.展开更多
基金the National Natural Science Foundation of China (Grant no. 40631006)the National Major Science Project of China for Global Change Research (Grant no. 2010CB951403)
文摘Abstract Monthly mean sea ice motion vectors and monthly mean sea level pressure （SLP） for the period of 1979-2006 are investigated to understand the spatial and temporal changes of Arctic sea-ice drift. According to the distinct differences in monthly mean ice velocity field as well as in the distribution of SLP, there are four primary types in the Arctic Ocean： Beaufort Gyre＋Transpolar Drift, Anticyclonic Drift, Cyclonic Drift and Double Gyre Drift. These four types account for 81% of the total, and reveal distinct seasonal variations. The Cyclonic Drift with a large-scale anticlockwise ice motion pattern trends to prevail in summer while the Anticyclonic Drift with an opposite pattern trends to prevail in winter and spring. The prevailing seasons for the Beaufort Gyre＋Transpolar Drift are spring and autumn, while the Double Gyre Drift trends to prevail in winter, especially in Feb- ruary. The annual occurring times of the Anticyclonic Drift and the Cyclonic Drift are closely correlated with the yearly mean Arc- tic Oscillation （AO） index, with a correlation coefficient of -0.54 and 0.54 （both significant with the confident level of 99%）, re- spectively. When the AO index stays in a high positive （negative） condition, the sea-ice motion in the Arctic Ocean demonstrates a more anticlockwise （clockwise） drifting pattern as a whole. When the AO index stays in a neutral condition, the sea-ice motion becomes much more complicated and more transitional types trend to take place.
基金Project supported by the State Science and Technology Committee of Chinathe National Natural Science Foundation of China and the State Committee for Antarctic Research of China.
文摘On the way of the '1990 International Trans-Antarctic Expedition', the first author of this paper, the Chinese member of the expedition, collected 104 snow samples in 25-cm surface snow along a 5986-km route on Antarctic ice sheet from west to east. The geographical distribution of δD across the Antarctica by the longest route is obtained from stable isotope analysis for the first time. After discussing regional differences of physical geographic conditions, maritime-continental influence, altitudes and latitudes at sampling sites, the distribution of δD is considered to have a close relation to latitudes, but the topographic effect is prominent in some particular regions. The mean annual temperature at sampling site and its relationship with δD in surface snow covering Antarctica from west to east are discussed also. The δD-temperature gradient from the south end of Antarctic Peninsula to Vostok obtained in this paper is very close to that in Terre Adelie Land obtained by predecessors. The snow-drift may make an important contribution to the relatively high δD-temperature gradient from Vostok to Mirnyy.
基金the National Science Foundation of China(Grant No.42401572)Natural Science Foundation of the Jiangsu Higher Education Institutions of China(Grant No.22KJB170023)Postgraduate Research&Practice Innovation Program of Jiangsu Province(No.KYCX24_3758).
文摘Water temperature is a critical indicator and weathervane of aquatic ecosystems.However,the vast majority of rivers lack long-term continuous and complete water temperature datasets.In this study,ensemble models by combining NARX(nonlinear autoregressive network with exogenous inputs)and air2stream were used to reconstruct daily river water temperatures for 27 hydrological stations in the Odra River Basin,one of the largest river systems in Europe.For each hydrological station,both the NARX and air2stream models were calibrated and validated,and the better-performed model was selected to reconstruct daily river water temperatures from 1985 to 2022.The results showed that hybrid modeling by combining NARX and air2stream is promising for reconstructing daily river water temperatures.Based on the reconstructed dataset,annual and seasonal trends of water temperature and characteristics of river heatwaves were evaluated.The results indicated that annual river water temperatures showed a consistent warming trend over the past 40 years with an average warming rate of 0.315C/decade.Seasonal river water temperatures indicated that summer warms faster,followed by autumn and spring,and winter river water temperatures showed an insignificant warming trend.River heatwaves are increased in frequency,duration,and intensity in the Odra River Basin,and 6 out of 27 hydrological stations have river heatwaves categorized as‘severe’and‘extreme’,suggesting that mitigation measures are needed to reduce the impact of climate warming on aquatic systems.Moreover,results showed that air temperature is the major controller of river heatwaves,and river heatwaves tend to intensify with the warming of air temperatures.
基金supported by the National Natural Science Foundation of China (U1603235, 31660127)the Tianshan Innovation Team Plan of Xinjiang (2017D14009)
文摘The association between biodiversity and belowground biomass(BGB) remains a central debate in ecology.In this study, we compared the variations in species richness(SR) and BGB as well as their interaction in the top(0–20 cm), middle(20–50 cm) and deep(50–100 cm) soil depths among 8 grassland types(lowland meadow, temperate desert, temperate desert steppe, temperate steppe desert, temperate steppe, temperate meadow steppe, mountain meadow and alpine steppe) and along environmental gradients(elevation, energy condition(annual mean temperature(AMT) and potential evapotranspiration(PET)), and mean annual precipitation(MAP)) based on a 2011–2013 survey of 379 sites in Xinjiang, Northwest China.The SR and BGB varied among the grassland types.The alpine steppe had a medium level of SR but the highest BGB in the top soil depth, whereas the lowland meadow had the lowest SR but the highest BGB in the middle and deep soil depths.The SR and BGB in the different soil depths were tightly associated with elevation, MAP and energy condition;however, the particular forms of trends in SR and BGB depended on environmental factors and soil depths.The relationship between SR and BGB was unimodal in the top soil depth, but SR was positively related with BGB in the middle soil depth.Although elevation, MAP, energy condition and SR had significant effects on BGB, the variations in BGB in the top soil depth were mostly determined by elevation, and those in the middle and deep soil depths were mainly affected by energy condition.These findings highlight the importance of environmental factors in the regulations of SR and BGB as well as their interaction in the grasslands in Xinjiang.
