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1.
This paper reveals the temporal and spatial variations of stable isotope in precipitation of the Yarlung Zangbo River Basin based on the variations of δ^18O in precipitation at four stations (Lhaze, Nugesha, Yangcun and Nuxia) in 2005. The results show that δ^18O of precipitation has distinct seasonal changes in the Yarlung Zangbo River Basin. The higher value of δ^18O occurs in spring prior to monsoon precipitation, and the lower value occurs during monsoon precipitation. From the spatial variations, with the altitude-effect and rainout process during moisture transport along the Yarlung Zangbo River Valley, δ^18O of precipitation is gradually depleted. Thus, δ^18O of precipitation decreases gradually from the downstream to the upstream, and the lapse rate of δ^18O in precipitation is approximately 0.34‰/100m and 0.7%J‰/100km for the two reasons. During monsoon precipitation, spatial variation of δ^18O in precipitation is dominated by the amount effect in the large scale synoptic condition.  相似文献   

2.
Surface snow samples of different altitudes and snow pit samples were collected from Glacier No.1 at the Urumqi River Head, Tianshan. Denaturing gradient gel electrophoresis (DGGE) was used to examine the diversity and temporal-spatial characteristics of eukaryotic microorganisms with different altitudes and depths. Results show that the eukaryotic microorganisms belong to four kingdoms—Viridiplantae, Fungi, Amoebozoa, and Alveolata. Among them, algae (especially Chlamydomonadales) were the dominant group. The diversity of eukaryotic microorganisms was negatively correlated with altitude and accumulation time, but positively correlated with δ18O values. These results indicate that temperature is the main factor for the temporal- spatial change of eukaryotic microorganisms, and the diversity of eukaryotic microorganisms could be an index for climate and environmental change.  相似文献   

3.
This paper reveals the temporal and spatial variations of stable isotope in precipita-tion of the Yarlung Zangbo River Basin based on the variations of δ18O in precipitation at four stations (Lhaze,Nugesha,Yangcun and Nuxia) in 2005. The results show that δ18O of pre-cipitation has distinct seasonal changes in the Yarlung Zangbo River Basin. The higher value of δ18O occurs in spring prior to monsoon precipitation,and the lower value occurs during monsoon precipitation. From the spatial variations,with the altitude-effect and rainout process during moisture transport along the Yarlung Zangbo River Valley,18O of precipitation is gradually depleted. Thus,δ18O of precipitation decreases gradually from the downstream to the upstream,and the lapse rate of δ18O in precipitation is approximately 0.34‰/100m and 0.7‰/100km for the two reasons. During monsoon precipitation,spatial variation of δ18O in precipitation is dominated by the amount effect in the large scale synoptic condition.  相似文献   

4.
Hydrological processes were compared,with and without the influence of precipitation on discharge,to identify the differences between glacierized and non-glacierized catchments in the Urumqi River source region,on the northern slope of the eastern Tianshan Mountains,during the melting season(May-September) in 2011.The study was based on hydrological data observed at 10-min intervals,meteorological data observed at 15-min intervals,and glacier melting and snow observations from the Empty Cirque,Zongkong,and Urumqi Glacier No.1 gauging stations.The results indicated that the discharge differed markedly among the three gauging stations.The daily discharge was more than the nightly discharge at the Glacier No.1 gauging station,which contrasted with the patterns observed at the Zongkong and Empty Cirque gauging stations.There was a clear daily variation in the discharge at the three gauging stations,with differences in the magnitude and duration of the peak discharge.When precipitation was not considered,the time-lags between the maximum discharge and the highest temperature were 1-3 h,10-16 h,and 5-11 h at the Glacier No.1,Empty Cirque,and Zongkong gauging stations,respectively.When precipitation was taken into consideration,the corresponding time-lags were 0-1 h,13 h,and 6-7 h,respectively.Therefore,the duration from the generation of discharge to confluence was the shortest in the glacierized catchment and the longest in the catchment where was mainly covered by snow.It was also shown that the hydrological process from the generation of discharge to confluence shortened when precipitation was considered.The factors influencing changes in the discharge among the three gauging stations were different.For Glacier No.1 station,the discharge was mainly controlled by heat conditions in the glacierized region,and the discharge displayed an accelerated growth when the temperature exceeded 5℃ in the melt season.It was found that the englacial and subglacial drainage channel of Glacier No.1 had become simpler during the past 20 years.Its weaker retardance and storage of glacier melting water resulted in rapid discharge confluence.It was also shown that the discharge curve and the time-lag between the maximum discharge and the highest temperature could be used to reveal the evolution of the drainage system and the process of glacier and snow melting at different levels of glacier coverage.  相似文献   

5.
Using the isotope enabled ECHAM4, GISS E and HadCM3 GCMs, the spatial distribution of mean δ18O in precipitation, mean seasonality and the correlations of δ18O in precipitation with temperature and precipitation amount are analyzed. The simulated results are in agreement with stable isotopic features by GNIP observations. Over East Asia, the distribution of δ18O in precipitation is of marked latitude effect and altitude effect. The latitude effect is covered by the continent effect in some regions. The largest seasonality of δ18O in precipitation appears in eastern Siberia controlled by cold high pressure, and the smallest seasonality is in the western Pacific controlled by the subtropical high. Relatively weak seasonality appears in middle latitudes where oceanic and continental air masses frequently interact. However, three GCMs show significant systematic lower δ18O for inland mid-high latitudes than GNIP data, which is related to the used isotopic scheme in GCMs. Temperature effect occurs mainly in inland mid-high latitudes. The higher the latitude and the closer the distance to inland is, then the stronger the temperature effect. Amount effect occurs mainly in low-mid latitudes and monsoon areas, with the strongest effect in low-latitude coasts or islands. However, three GCMs provide virtually non-existent amount effect in arid regions over Central Asia. The enrichment action of stable isotopes in falling raindrops under a cloud base, which is enlarged by these modes, is responsible for such a result. A significant difference between spatial distributions of δ18O statistics by GCMs simulations and by GNIP observations is that the standard deviation of GCMs statistics is greater than that of GNIP statistics. In contrast, by comparing parallel time series at a single station, the standard deviations of GCMs simulations are smaller than that of GNIP observations.  相似文献   

6.
A 70-year history of precipitation δ18O record has been retrieved using an ice core drilled from a plat portion of the firn area in the Guoqu Glacier (33o34′37.8″ N, 91o10′35.3″ E, 5720 m a.s.l.) on Mt. Geladaindong (the source region of Yangtze River) during October and November, 2005. Based on the seasonality of δ18O records and the significant positive relationships between monsoon/non-monsoon δ18O values and summer/spring air temperature from the nearby meteorological stations, the history of summer and spring air temperature have been reconstructed for the last 70 years. The results show that both summer and spring air temperature variations present similar trends during the last 70 years. Regression analysis indicates that the slope of the temperature-δ18O relationship is 1.3℃/‰ for non-monsoon δ18O values and spring air temperature, and 0.4℃/‰ for monsoon δ18O values and summer air temperature. Variation of air temperature recorded in the ice core is consistent with that in the Northern Hemisphere (NH), however, the warming trend in the Geladaindong region is more intense than that in the NH, reflecting a higher sensitivity to global warming in the high elevation regions. In addition, warming trend is greater in spring than in summer.  相似文献   

7.
Seasonal variation of stable isotopes in precipitation of Kathmandu Valley on the southern slope of Himalaya was carried out to understand the controlling mechanism of amount and temperature effect on the basis of one year stable isotope data from 2010 to 2011. Highly depleted isotope values in major rainy period are obtained just after the onset of precipitation in summer, which accounts for "amount effect" due to saturation isotopic compositions in high moisture condition, whereas, the higher values in winter are indicative to regional vapors (temperature effect) recycling of various sources. An abrupt depletion of isotope values in mid-June, indicates the onset date of monsoon precipitation, by the replacement of winter air mass with southern monsoon. Thus, precipitation isotopes are a tool revealing the onset date of summer monsoon and temporal features of variability, in local and regional monsoons precipitations. A comparison of long term monthly values of δ 18 O, temperature, and precipitation with GNIP δ 18 O data shows the temporal variations of stable isotopes are mostly controlled by amount and temperature effects. During summer monsoon, the amount effects are stronger for high values of precipitation (R=0.7) and altitude effect appears for low moisture in late rainy season, thus from December to June (winter to pre-monsoon) the controlling features of isotopes remains under the temperature effect. A temporal rate of temperature effect is derived as 0.04‰ per year which indicates a dry signal of atmospheric condition and a temperature relation δ 18 O=(0.371±0.08)T+(0.156±0.05) is obtained from this analysis. The meteoric water lines of Kathmandu before and after monsoon onset of 2011, are found as δD=(4.36±0.3)δ 18 O+(15.66±1.2) and δD=(6.91±0.2)δ 18 O (7.92±2.26) from lab samples result, and δD=9.2δ 18 O+11.725 and δD=8.53δ 18 O+16.65 from GNIP data, which lacks the consistency both for slopes and intercepts values for the study period. The mean lapse rate values of δ 18 O and δD from GNIP data are obtained as 0.002‰/m and 0.015 ‰/m, which indicate the altitudinal effects in regional precipitation of the southern slope of Himalayas. This study estimates new stable isotopes data in recent precipitation using simple methodology which can be important for regional precipitation monitoring systems, environmental change and paleo-climatic studies.  相似文献   

8.
Seasonal variation of stable isotopes in precipitation of Kathmandu Valley on the southern slope of Himalaya was carried out to understand the controlling mechanism of amount and temperature effect on the basis of one year stable isotope data from 2010 to 2011. Highly depleted isotope values in major rainy period are obtained just after the onset of precipitation in summer, which accounts for "amount effect" due to saturation isotopic compositions in high moisture condition, whereas, the higher values in winter are indicative to regional vapors (temperature effect) recycling of various sources. An abrupt depletion of isotope values in mid- June, indicates the onset date of monsoon precipitation, by the replacement of winter air mass with southern monsoon. Thus, precipitation isotopes are a tool revealing the onset date of summer monsoon and temporal features of variability, in local and regional monsoons precipitations. A comparison of long term monthly values of δ18O, temperature, and precipitation with GNIP δ18O data shows the temporal variations of stable isotopes are mostly controlled by amount and temperature effects. During summer monsoon, the amount effects are stronger for high values of precipitation (R=0.7) and altitude effect appears for low moisture in late rainy season, thus from December to June (winter to pre-monsoon) the controlling features of isotopes remains under the temperature effect. A temporal rate of temperature effect is derived as 0.04‰ per year which indicates a dry signal of atmospheric condition and a temperature relation δ18O=(0.371±0.08)T+(0.156±0.05) is obtained from this analysis. The meteoric water lines of Kathmandu before and after monsoon onset of 2011, are found as δD=(4.36±0.3)δ18O+(15.66±1.2) and δD=(6.91±0.2)δ18O?(7.92±2.26) from lab samples result, and δD=9.2δ18O+11.725 and δD=8.53δ18O+16.65 from GNIP data, which lacks the consistency both for slopes and intercepts values for the study period. The mean lapse rate values of δ18O and δD from GNIP data are obtained as ?0.002‰/m and ?0.015 ‰/m, which indicate the altitudinal effects in regional precipitation of the southern slope of Himalayas. This study estimates new stable isotopes data in recent precipitation using simple methodology which can be important for regional precipitation monitoring systems, environmental change and paleo-climatic studies.  相似文献   

9.
中国南部夏季季风降水水汽来源的稳定同位素证据   总被引:2,自引:0,他引:2  
Summer monsoons (South Asian monsoon, South China Sea monsoon and Subtropical monsoon) are prominent features of summertime climate over southern China. Dif- ferent monsoons carry different inflow moisture into China and control the temporal and spatial distributions of precipitation. Analyses of meteorological data, particularly wind, tempera- ture and pressure anomalies are traditional methods of characterizing moisture sources and transport patterns. Here, we try to utilize the evidence from stable isotopes signatures to trace summer monsoons over southern China. Based on seven CHNIP (Chinese Network of Iso- topes in Precipitation) observatory stations located in southern China, monthly composite precipitation samples have been collected and analyzed for the composition of δ^18O during July, 2005. The results indicated that the spatial distributions of δ^18O in precipitation could properly portray the moisture sources together with their transport pathways. Moreover, the amount effect, altitude effect, temperature effect and the correlation between δ^18O vs. relative humidity were discussed.  相似文献   

10.
三江源地区气候变化及其对径流的驱动分析(英文)   总被引:6,自引:3,他引:3  
Based on the precipitation and temperature data of the 12 meteorological stations in the "Three-River Headwaters" region and the observed runoff data of Zhimenda in the headwater sub-region of the Yangtze River, Tangnaihai in the headwater sub-region of the Yellow River and Changdu in the headwater sub-region of the Lancang River during the period 1965-2004, this paper analyses the trends of precipitation, temperature, runoff depth and carries out significance tests by means of Mann-Kendall-Sneyers sequential trend test. Makkink model is applied to calculate the potential evaporation. The runoff model driven by precipitation and potential evaporation is developed and the influence on runoff by climate change is simulated under different scenarios. Results show that during the period 1965-2004 the temperature of the "Three-River Headwaters" region is increasing, the runoff of the three hydrological stations is decreasing and both of them had abrupt changes in 1994, while no significant trend changes happen to the precipitation. The runoff model suggests that the precipitation has a positive effect on the runoff depth, while the potential evaporation plays a negative role. The influence of the potential evaporation on the runoff depth of the Lancang River is found to be the significant in the three rivers; and that of the Yellow River is the least. The result of the scenarios analysis indicates that although the precipitation and the potential evaporation have positive and negative effects on runoff relatively, fluctuated characteristics of individual effect on the runoff depth in specific situations are represented.  相似文献   

11.
Oxygen-18 in different waters in Urumqi River Basin   总被引:1,自引:0,他引:1  
The variations of the stable oxygen isotope in different water mediums in Urumqi River Basin, China, are analyzed. The stable oxygen isotope in precipitation has marked temperature effect either under synoptic or seasonal scale at the head of Urumqi River. The linear regression equations of δ18O against temperature are δ18O=0.94T-12.38 and δ18O=1.29T-13.05 under the two time scales, respectively. The relatively large δ18O/temperature slopes show the strong sensitivity of δ18O in precipitation to temperature variation at the head of Urumqi River. According to the analyses on the δ18O in precipitation sampled at three stations with different altitudes along Urumqi River, altitude effect is notable in the drainage basin. The δ18O/altitude gradients have distinct differences: the gradient from Urumqi to Yuejinqiao is merely -0.054‰/hm, but -0.192‰/hm from Yuejinqiao to Daxigou, almost increasing by 2.6 times over the former. No altitude effect is found in surface firn in the east branch of Glacier No.1 at the head of Urumqi River, showing that precipitation in the glacier is from the cloud cluster with the same condensation level. Influenced by strong ablation and evaporation, the δ18O in surface firn increases with increasing altitude sometimes. Survey has found that the δ18O in meltwater at the terminus of Glacier No.1 and in stream water at Total Control have the similar change trend with the former all smaller than the latter, which displays the different runoff recharges, and all mirror the regime of temperature in the same term basically.  相似文献   

12.
We quantified differences in oxygen isotope fractionation among three biostratigraphically important subfossil ostracod species (Metacypris cordata, Pseudocandona rostrata and Candonopsis kingsleii) from an early Holocene freshwater tufa layer in northern Estonia. Estimated mean δ18O values are −10.05‰ for M. cordata, −9.34‰ for C. kingsleii and −8.75‰ for P. rostrata. All three species exhibit positive offset from the weighted mean annual δ18O of contemporary precipitation (−10.7‰ in δ18OV-PDB) and from the mean δ18O value of authigenic tufa carbonate (−10.64‰) in the ostracod-bearing layer. Assuming that the known oxygen isotope fractionation in P. rostrata (+2.5‰) and M. cordata (+1.5‰) has remained constant over time, the theoretical δ18OV-SMOW of the early Holocene lake water was calculated to have been between −11.52 and −11.92‰, slightly less negative than the local Ordovician groundwater (−11.7 to −12.2‰). δ18O values of the tufa carbonate differ by +0.6 to +1.0‰ from the calculated theoretical isotope composition (δ18OV-PDB) of lake water, indicating that the tufa also did not precipitate in isotopic equilibrium with ambient waters. Results show that the greater the δ18O offset from the calculated, theoretical isotope composition of lake water for an ostracod species, the lower is its preferred mean July temperature. Both our data and earlier published results on δ18O values in Holocene lacustrine carbonates and ostracods from north-eastern Europe, display pronounced decreases in δ18O with an increase in latitude of the study site. This suggests that temperature-dependent, and therefore latitude-dependent isotopic composition of meteoric waters controlled the δ18O values in lacustrine tufa and ostracods throughout the Holocene.  相似文献   

13.
The spatial and temporal variations of stable oxygen isotope in precipitation on different time scales are analyzed according to the data from the IAEA/WMO stations with long survey series in the Northern Hemisphere. Temperature effect is mainly distributed in mid-high latitudes on seasonal scale except for Bamako and Addisababa stations. The δ18O/temperature slope displays the positive correlation against altitude for most of the statistical stations. Amount effect appears primarily in the region south of 30°N and coastal areas. The δ18O/precipitation slope is indirectly proportional to precipitation amount. For some of the sampling stations at mid-high latitudes where their seasonal distribution of precipitation is contrary to that of temperature, coupled with temperature effect, the amount effect appears synchronistically. Either the temperature effect or the amount effect on seasonal scale, there are positive correlations to a certain extent between the annual weighted mean δ18O and the annual mean temperature for almost all the stations. The correlation between composite δ18O and temperature on spatial scale is much more marked, compared with that of individual station. There is a good agreement between 10-year moving average temperature curves I and II, with the values of the former all markedly smaller than corresponding ones of the latter, calculated by the monthly mean series group I and the annual mean series group II, respectively. However, two calculated dδ18O/dT curves display the distinct difference: the variation amplitude of slope series II is larger than that of slope series I. Both curves had similar ascending trend from the 1960s to the 1970s, and then, their variations display the anti-phase. Moreover, the analyses show that there is negative correlation between slope series FI and temperature series II. However, the status is different for slope series I and temperature series I. Both series have contrary trend from the 1960s to the 1970s, whereas the same trend since the 1980s.  相似文献   

14.
西北干旱地区大气降水δ18O的特征及水汽来源   总被引:7,自引:1,他引:6  
In order to reveal the characteristics and climatic controls on the stable isotopic composition of precipitation over Arid Northwestern China, eight stations have been selected from Chinese Network of Isotopes in Precipitation (CHNIP). During the year 2005 and 2006, monthly precipitation samples have been collected and analyzed for the composition of δD and δ18O. The established local meteoric water line δD=7.42 δ18O+1.38, based on the 95 ob-tained monthly composite samples, could be treated as isotopic input function across the region. The deviations of slope and intercept from the Global Meteoric Water Line indicated the specific regional meteorological conditions. The monthly δ18O values were characterized by a positive correlation with surface air temperature (δ18O (‰) =0.33 T (℃)-13.12). The amount effect visualized during summer period (δ18O (‰) = -0.04P (mm)-3.44) though not appeared at a whole yearly-scale. Spatial distributions of δ18O have properly portrayed the atmospheric circulation background in each month over Arid Northwestern China. The quan-titative simulation of δ18O, which involved a Rayleigh fractionation and a kinetic fractionation, demonstrated that the latter one was the dominating function of condensation of raindrops. Furthermore, the raindrop suffered a re-evaporation during falling processes, and the pre-cipitation vapor might have been mixed with a quantity of local recycled water vapor. Multiple linear regression equations and a δ18O-T relation have been gained by using meteorological parameters and δ18O data to evaluate physical controls on the long-term data. The estab-lished δ18O-T relation, which has been based on the present-day precipitation, could be considered as a first step of quantitatively reconstructing the historical environmental climate.  相似文献   

15.
We present results from multiple stable isotope analyses (δ18O of chironomid larval head capsules, chironomid adult thoraxes and other insect remains and δD, δ13C, δ15N of total organic matter—TOM) of a lake sediment core (04-SVID-03) taken from Stora Vidarvatn in northeastern Iceland to reconstruct past environmental, limnological and δ18O of past lake water changes during the Holocene. Core 04-SVID-03 represents a ∼12,000 cal. yrs BP to present record. Large magnitude changes in δ18O occurred during the Holocene at the site. Downcore shifts in δ18O of chironomids did not correlate with measurements of the δ13C and δ15N of chironomid head capsules, implying that the δ18O changes were not primarily driven by changes in chironomid diet during the Holocene. The δD of TOM provided a proxy of relative lake-water δD changes at the site and also showed large magnitude changes during the record. This approach was supported by analyses of a modern training set where δDTOM analyses were conducted using surface sediments from a suite of freshwater lakes over a large latitudinal gradient. The magnitude of changes in both the δ18O and δD and the relatively negative δ18O values throughout much of the core suggest that the proxies represent more paleoenvironmental information than solely temperature. Additional possible influences on lake-water isotopic composition are discussed, including changes in the seasonality of precipitation, in the patterns of air masses supplying precipitation to Iceland and in the dominant mode of the North Atlantic Oscillation.  相似文献   

16.
Stable isotopes (δ18O and δD) are useful tracers for investigating hydrologic and climatic variability on a variety of temporal and spatial scales. Since the early isotopic studies on mountainous glaciers in the late 1960s, a great deal of information has been generated on the isotopic composition of rainfall, snow, ice, surface waters, and lake carbonate sediments across the Tibetan Plateau. However, measurements of δ18O and δD values of lake water are scarce. Here we present a new dataset of δ18O and δD values of lake waters collected from 27 lakes across the plateau during a reconnaissance survey in summer 2009. δ18O and δD values of lake water range from −19.9 to 6.6‰ and from −153 to −16‰, respectively. The average values of δ18O and δD are −6.4 and −72‰, considerably greater than those of precipitation observed in this region. The derived Tibetan lake water line, δD = 5.2δ18O − 38.9, is significantly different from the global meteoric water line. Most of the lakes, including some freshwater lakes, contain water with negative values of d-excess (d). There is a negative correlation between d and total dissolved solids (TDS). Each of these findings indicates that evaporation-induced isotopic enrichment prevails in Tibetan lakes. Moreover, we develop an isotope modeling scheme to calculate E/P ratios for Tibetan lakes, using a combination of existing isotopic fractionation equations and the Rayleigh distillation model. We use the intersection of the local evaporation line and GMWL as a first approximation of δ18O and δD values of lake water inputs to infer an E/P ratio for each lake. Our modeling calculations reveal that although variable from lake to lake, the water budget across the plateau is positive, with an average E/P of 0.52. This is in good agreement with other observational and model data that show varying degrees of increases in lake size from satellite imagery and significant decreases in lake salinity in many lakes on the plateau over the last several decades. Together with the new isotopic dataset, the proposed modeling framework can be used to examine and quantify past changes in a lake’s hydrologic balance from the isotopic record of downcore carbonate sediments in the region.  相似文献   

17.
During the 1992-1993 joint Australian-Chinese over-snow traverse of the western Lambert Glacier Basin (LGB), two firn cores were drilled respectively at MGA and LGB16. During the 1996-1997 and 1997-1998 austral summers, two firn cores were drilled respectively at DT001 and DT085 on the eastern LGB. Based on the measurements made during the expeditions, the climatic and environmental features on both sides of the LGB have been studied. Results show that during the past 50 years, the trends of both air temperature and accumulation rate show a slight increase on the east side of the LGB, in contrast to the west side of the LGB. The spatial trends of the accumulation rate measured by accumulation canes at 2 km intervals along the nearly 500 km of the traverse lines on both sides of the LGB are different. Moreover, correlations of δ^18O vs T10 along the two sides of the LGB are also different. In addition, the variations of sea salt ion concentrations show different trends in the past 50 years. All the evidence shows that the Lambert Glacier is a dividing region for the different climatic regimes over the East Antarctic ice sheet, which may be due to different moisture resources resulting from special local circumfluence such as cyclone activities, local terrain influences.  相似文献   

18.
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