Glacier changes in the eastern Nyainqêntanglha Range of Tibetan Plateau from 1975 to 2013     

JI Qin  YANG Tai-bao  HE Yi  CHEN Jie  WANG Kai 《山地科学学报》2016,13(4):682-692

Maritime-type glaciers in the eastern Nyainqêntanglha Range, located in the southeastern part of the Tibetan Plateau, are an important water source for downstream residents and ecological systems. To better understand the variability of glaciers in this region, we used the band ratio threshold(TM3/TM5 for the Landsat TM /ETM+ and TM4/TM6 for Landsat OLI) to extract glacier outlines in ~1999 and ~2013. After that, we also generated a series of glacier boundaries and monitored glacier variations in the past 40 years with the help of the Chinese Glacier Inventory data(1975) and Landsat TM, ETM+ and OLI data. The total glacier area decreased by 37.69 ± 2.84% from 1975 to 2013. The annual percentage area change(APAC) was ~1.32% a-1 and ~1.29% a-1 in the periods 1975-1999 and 1999-2013, respectively. According to the lag theory, the reaction time is probably about 10 years and we discuss the variations of temperature and precipitation between 1965 and 2011. Temperature and precipitation increased between 1965 and 2011 at a rate of 0.34°C /10 a and 15.4 mm/10 a, respectively. Extensive meteorological data show that the glacier shrinkage rate over the period may be mainly due to increasing air temperature, while the increasing precipitation partly made up for the mass loss of glacier ice resulting from increasing temperature may also lead to the low APAC between 1999 and 2013. The lag theory suggests that glacier shrinkage may accelerate in the next 10 years. Small glaciers were more sensitive to climate change, and there was a normal distribution between glacier area and elevation. Glaciers shrank in all aspects, and south aspects diminished faster than others.  相似文献   

Depth classification of underwater targets based on complex acoustic intensity of normal modes     

Guang?Yang  Jingwei?YinEmail author  Yun?Yu  Zhenhua?Shi 《中国海洋大学学报(英文版)》2016,15(2):241-246

In order to solve the problem of depth classification of the underwater target in a very low frequency acoustic field, the active component of cross spectra of particle pressure and horizontal velocity (ACCSPPHV) is adopted to distinguish the surface vessel and the underwater target. According to the effective depth of a Pekeris waveguide, the placing depth forecasting equations of passive vertical double vector hydrophones are proposed. Numerical examples show that when the sum of depths of two hydrophones is the effective depth, the sign distribution of ACCSPPHV has nothing to do with horizontal distance; in addition, the sum of the first critical surface and the second critical surface is equal to the effective depth. By setting the first critical surface less than the difference between the effective water depth and the actual water depth, that is, the second critical surface is greater than the actual depth, the three positive and negative regions of the whole ocean volume are equivalent to two positive and negative regions and therefore the depth classification of the underwater target is obtained. Besides, when the 20 m water depth is taken as the first critical surface in the simulation of underwater targets (40 Hz, 50 Hz, and 60 Hz respectively), the effectiveness of the algorithm and the correctness of relevant conclusions are verified, and the analysis of the corresponding forecasting performance is conducted.  相似文献   

Tropical Atlantic climate response to different freshwater input in high latitudes with an ocean-only general circulation model     

Guang?Men  Xiuquan?WanEmail author  Zedong?Liu 《中国海洋大学学报(英文版)》2016,15(5):751-757

Tropical Atlantic climate change is relevant to the variation of Atlantic meridional overturning circulation (AMOC) through different physical processes. Previous coupled climate model simulation suggested a dipole-like SST structure cooling over the North Atlantic and warming over the South Tropical Atlantic in response to the slowdown of the AMOC. Using an ocean-only global ocean model here, an attempt was made to separate the total influence of various AMOC change scenarios into an oceanic-induced component and an atmospheric-induced component. In contrast with previous freshwater-hosing experiments with coupled climate models, the ocean-only modeling presented here shows a surface warming in the whole tropical Atlantic region and the oceanic-induced processes may play an important role in the SST change in the equatorial south Atlantic. Our result shows that the warming is partly governed by oceanic process through the mechanism of oceanic gateway change, which operates in the regime where freshwater forcing is strong, exceeding 0.3 Sv. Strong AMOC change is required for the gateway mechanism to work in our model because only when the AMOC is sufficiently weak, the North Brazil Undercurrent can flow equatorward, carrying warm and salty north Atlantic subtropical gyre water into the equatorial zone. This threshold is likely to be model-dependent. An improved understanding of these issues may have help with abrupt climate change prediction later.  相似文献   

Mechanisms of partly flooded loose sand deposits     

Gerd?GudehusEmail author 《Acta Geotechnica》2016,11(3):505-517

Partly flooded loose sand deposits are left back from lignite mining, particularly in east Germany. After flooding, gas inclusions in macropores enhance the pore pressure increase by total stress cycles without drainage, and this can cause the transition into a kind of suspension. Thus, natural and technical changes of surface loads triggered flow slides in chain reactions of sometimes catastrophic extent. Such collapsible deposits were and are stabilized by blast-induced liquefaction and densification. Successive collapse fronts in flooded grain skeletons are seismogeneous, and this appears as wavering in the near-field and leads to power-law spectra in the far-field. Apart from this evidence of mild fractality, the wild fractality of chain reactions eludes mathematical treatment. Therefore, uncommon methods of geotechnical design, operations and monitoring are required.  相似文献   

Large-scale,seasonal flood risk analysis for agricultural crops in Germany     

Stefan Klaus  Heidi Kreibich  Bruno Merz  Bernd Kuhlmann  Kai Schröter 《Environmental Earth Sciences》2016,75(18):1289

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Characteristics of deuterium excess parameters for geothermal water in Beijing     

Kai Liu  Xiaojuan Qiao  Baoling Li  Ying Sun  Zhiping Li  Conglin Pu 《Environmental Earth Sciences》2016,75(23):1485

This study investigates the characteristics of geothermal water in 10 geothermal fields in Beijing. The relationships between the deuterium excess parameter (d) and temperature, depth, age of geothermal groundwater, groundwater flow field, and Eh were investigated using geothermal groundwater samples. Results showed that (1) the average d value of geothermal water is 5.4, whereas that of the groundwater in normal temperature is 6.04. The differences are induced by the oxygen isotope exchange during the water–rock interaction, which may be more easily completed in geothermal water than in cold groundwater. (2) The d value increases remarkably with the age of the geothermal groundwater. The d value increases from 11.2 to 14.6 when the age of the geothermal water is 12,760 ± 130 a and 38,960 ± 630 a, respectively. Moreover, the isotope heat exchange for composition of the hydrogen and oxygen isotopes in the geothermal groundwater proceeds sufficiently with time. (3) The d value decreases from 5.72 to 3.03 when the depth increases from 125.13 to 3221 m. Generally, in the same area, the d value decreases with depth because the temperature is increasing. (4) The d value of the groundwater gradually reduces from the northern recharge area to the southern discharge area. The average d value is 7.31 in the northern recharge area and 5.68 in the middle Beijing Depression, whereas the d value in the southern area of Fengheying is ?9.20. The larger difference in d values between the recharge and discharge areas is due to the slower velocity of underwater flow, which induces longer time for oxygen exchange. (5) The relationship between the d and Eh is complex. When Eh is <200 mV, the d value of the geothermal water decreases with the decrease in Eh. When Eh is higher than 200 mV, the d value increases slightly with the decrease in Eh. The study of the characteristics of deuterium excess parameters for geothermal water could provide a scientific isotopic evidence for assessment and exploitation measures in geothermal groundwater systems.  相似文献   

Intrinsic groundwater vulnerability determination at the aquifer scale: a methodology coupling travel time estimation and rating methods     

Vassilios?Pisinaras  Christos?Polychronis  Alexandra?GemitziEmail author 《Environmental Earth Sciences》2016,75(1):85

Groundwater vulnerability has been subject of much research due to the valuable information it provides concerning groundwater protection and exploitation potential. Up to now, most groundwater vulnerability studies adopt subjective systems of rating the various factors and subsequently, their results are often ambiguous and contradicting. Within the present study a methodology for the estimation of intrinsic groundwater vulnerability at the aquifer scale is presented. The methodology is based on travel time estimation from specified sources of pollution to the aquifer. Besides the deterministic calculation of travel times, the methodology provides a rating system for each pollution source, based on its relative severity and the estimated threat that it poses to the aquifer. Therefore, it can be regarded as a hybrid method that couples the advantages provided by the physically based methods with those of the subjective rating systems. The methodology is applied to the Neon Sidirochorion aquifer, Northeastern Greece, an overexploited aquifer where river waters, sea waters and lake waters interact, causing groundwater quality deterioration to the aquifer. The results indicated that the proposed groundwater vulnerability assessment methodology is well capturing pollution related to saltwater intrusion and agricultural activities, while it is concluded that the conceptual model is significantly affecting the vulnerability assessment results and therefore has to be previously developed.  相似文献   

Estimation of air-overpressure produced by blasting operation through a neuro-genetic technique     

Edy?Tonnizam Mohamad  Danial?Jahed ArmaghaniEmail author  Mahdi?Hasanipanah  Bhatawdekar?Ramesh?Murlidhar  Mohd?Nur?Asmawisham?Alel 《Environmental Earth Sciences》2016,75(2):174

Blasting operations usually produce significant environmental problems which may cause severe damage to the nearby areas. Air-overpressure (AOp) is one of the most important environmental impacts of blasting operations which needs to be predicted and subsequently controlled to minimize the potential risk of damage. In order to solve AOp problem in Hulu Langat granite quarry site, Malaysia, three non-linear methods namely empirical, artificial neural network (ANN) and a hybrid model of genetic algorithm (GA)–ANN were developed in this study. To do this, 76 blasting operations were investigated and relevant blasting parameters were measured in the site. The most influential parameters on AOp namely maximum charge per delay and the distance from the blast-face were considered as model inputs or predictors. Using the five randomly selected datasets and considering the modeling procedure of each method, 15 models were constructed for all predictive techniques. Several performance indices including coefficient of determination (R ²), root mean square error and variance account for were utilized to check the performance capacity of the predictive methods. Considering these performance indices and using simple ranking method, the best models for AOp prediction were selected. It was found that the GA–ANN technique can provide higher performance capacity in predicting AOp compared to other predictive methods. This is due to the fact that the GA–ANN model can optimize the weights and biases of the network connection for training by ANN. In this study, GA–ANN is introduced as superior model for solving AOp problem in Hulu Langat site.  相似文献   

Study on Longitudinal Deformation Profile of Rock Mass in a Subsea Tunnel     

Shu-Guang Song  Shu-Cai Li  Li-Ping Li  Qian-Qing Zhang  Kai Wang  Yi Zhou 《Marine Georesources & Geotechnology》2016,34(4):376-383

During tunnel excavation, the deformation of surrounding rock due to the unloading of rock mass will vary with time. However, the measured displacement of surrounding rock is only a part of the actual longitudinal deformation profile. There is a need to analyze the longitudinal deformation profile to identify the deformation state and evaluate the stability of surrounding rock mass. In the present article, the variation of pre-deformation of surrounding rock due to excavation was analyzed, and the release coefficient was obtained from the measured results. For the Qingdao subsea tunnel, the measured crown settlement of surrounding rock was analyzed using the regression analysis method, and the longitudinal deformation profile of rock mass was simulated using the numerical calculation method. Moreover, based on the conditions of the subsea tunnel, a solid-fluid coupling model test was carried out to check the reliability of the numerical calculation results. The results of the model test were consistent with the numerical calculation results.  相似文献   

Soil phosphorus composition and phosphatase activities along altitudes of alpine tundra in Changbai Mountains,China   总被引：1，自引：0，他引：1  

Xiaozhu Yang  Kai Wei  Zhenhua Chen  Lijun Chen 《中国地理科学(英文版)》2016,26(1):90-98

Alpine tundra ecosystems have specific vegetation and environmental conditions that may affect soil phosphorus(P) composition and phosphatase activities. However, these effects are poorly understood. This study used Na OH-EDTA extraction and solution31 P nuclear magnetic resonance(NMR) spectroscopy to determine soil P composition and phosphatase activities, including acid phosphomonoesterase(Ac P), phosphodiesterase(PD) and inorganic pyrophosphatase(IPP), in the alpine tundra of the Changbai Mountains at seven different altitudinal gradients(i.e., 2000 m, 2100 m, 2200 m, 2300 m, 2400 m, 2500 m, and 2600 m). The results show that total P(TP), organic P(OP), OP/TP, Na OH-EDTA extracted P and AcP, PD, and IPP activities over the altitude range of 2500–2600 m are significantly lower than those below 2400 m. The dominant extracted form of P is OP(73%–83%) with a large proportion of monoesters(65%–72%), whereas inorganic P is present in lower proportions(17%–27%). The activity of Ac P is significantly positively correlated with the contents of soil OP, total carbon(TC), total nitrogen(TN), and TP(P 0.05), indicating that the Ac P is a more sensitive index for responding P nutrient storage than PD and IPP. Soil properties, P composition, and phosphatase activities decrease with increased altitude and soil p H. Our results indicate that the distribution of soil P composition and phosphatase activities along altitude and Ac P may play an important role in P hydrolysis as well as have the potential to be an indicator of soil quality.  相似文献