The detection of glacial lake change in the Himalayas, Nepal is extremely significant since the glacial lake change is one of the crucial indicators of global climate change in this area, where is the most sensitive a...The detection of glacial lake change in the Himalayas, Nepal is extremely significant since the glacial lake change is one of the crucial indicators of global climate change in this area, where is the most sensitive area of the global climate changes. In the Hima- layas, some of glacial lakes are covered by the dark mountains' shadow because of their location. Therefore, these lakes can not be de- tected by conventional method such as Normalized Difference Water Index (NDWI), because the reflectance feature of shadowed glacial lake is different comparing to the ones which are located in the open flat area. The shadow causes two major problems: 1) glacial lakes which are covered by shadow completely result in underestimation of the number of glacial lakes; 2) glacial lakes which are partly iden- tified are considered to undervalue the area of glacial lakes. The aim of this study is to develop a new model, named Detection of Shadowed Glacial Lakes (DSGL) model, to identify glacial lakes under the shadow environment by using Advanced Space-borne Ther- mal Emission and Reflection Radiometer (ASTER) data in the Himalayas, Nepal. The DSGL model is based on integration of two dif- ferent modifications of NDWI, namely NDWls model and NDWIshe model. NDWI~ is defined as integration of the NDWI and slope analysis and used for detecting non-shadowed lake in the mountain area. The NDWIshe is proposed as a new methodology to overcome the weakness of NDWI~ on identifying shadowed lakes in highly elevated mountainous area such as the Himalayas. The first step of the NDWIshe is to enhance the data from ASTER 1B using the histogram equalization (HE) method, and its outcome product is named AS- TERho. We used the ASTERhe for calculating the NDWIhc and the NDWIshe. Integrated with terrain analysis using Digital Elevation Model (DEM) data, the NDWIshe can be used to identify the shadowed glacial lakes in the Himalayas. NDWIs value of 0.41 is used to identify the glacier lake (NDWI~ 〉 0.41), and 0.3 of NDWIshe is used to identify the shadowed glacier lake (NDWIsho 〈 0.3). The DSGL model was proved to be able to classify the glacial lakes more accurately, while the NDWI model had tendency to underestimate the presence of actual glacial lakes. Correct classification rate regarding the products from NDWI model and DSGL model were 57% and 99%, respectively. The results of this paper demonstrated that the DSGL model is promising to detect glacial lakes in the shadowed en- vironment at high mountains.展开更多
Study results in this paper have indicated that the Holocene climate in Xinjiang, Northwestem China has been alternating between wet and dry conditions, and was punctuated with a series of abrupt climate shifts. A sed...Study results in this paper have indicated that the Holocene climate in Xinjiang, Northwestem China has been alternating between wet and dry conditions, and was punctuated with a series of abrupt climate shifts. A sediment core taken from Barkol Lake in the northern Xinjiang of Northwest China was analyzed at 1 cm interval for grain-size distribution. Abrupt climate shifts revealed by the grain-size proxy occurred at ca 1.4, 3.0, 4.3, 5.6, 8.0 cal kyr B.E, which were well correlated to both the abrupt shifts recorded in the North Atlantic Ocean (NAO) and the Holocene sea surface temperature (SST) cooling events in the Arabian Ocean. The correlation indicated that the climatic changes in the extreme arid Northwest China were associated with the NAO, probably via the North Atlantic Oscillation-affected westerly winds. The strength and position of westerly winds probably modulated the Siberian-Mongolian high- pressure system (winter monsoon), and played an important role in climate change of Northwest China. Moreover, an evident drought interval during the middle Holocene was also revealed by grain-size proxy.展开更多
Traditionally, the mid-Holocene in most parts of China was thought to be warmer with higher precipitation, resulting from a strong Asian summer monsoon. However, some recent researches have proposed a mid-Holocene dro...Traditionally, the mid-Holocene in most parts of China was thought to be warmer with higher precipitation, resulting from a strong Asian summer monsoon. However, some recent researches have proposed a mid-Holocene drought interval of millennial-scale in East Asian monsoon margin areas. Thus whether mid-Holocene was dry or humid remains an open issue. Here, Zhuyeze palaeolake, the terminal lake of the Shiyang River Drainage lying in Asian monsoon marginal areas, was selected for reconstructing the details of climate variations during the Holocene, especially mid-Holocene, on the basis of a sedimentological analysis. Qingtu Lake (QTL) section of 6.92m depth was taken from Zhuyeze palaeolake. Multi-proxy analysis of QTL section, including grain size, carbonate, TOC, C/N and δ13C of organic matter, was used to document regional climatic changes during 9-3 cal ka B.P. The record shows a major environmental change at 9.0-7.8 cal ka B.P., attributed to a climate trend towards warmth and humidity. This event was followed by a typical regional drought event which occurred during 7.8-7.5 cal ka B.P. And a warm and humid climate prevailed from 7.5 to 5.0 cal ka B.P., attributed to the warm/humid Holocene Optimum in this region. After that, the climate gradually became drier. Moreover, comparison of the climate record from this paper with the summer insolation at 30°N indicates that the climate pattern reflecting the Asian monsoon changes was caused by insolation change.展开更多
Information on the palaeoenvironm ent from Late Pleistocene to Holocen e in northwestern Yannan Plateau has been deduced from a study of a 28.81m-long core taken from Napahai Lake.The results from Relative Brightness ...Information on the palaeoenvironm ent from Late Pleistocene to Holocen e in northwestern Yannan Plateau has been deduced from a study of a 28.81m-long core taken from Napahai Lake.The results from Relative Brightness In-dex(RBI )as well as those from the lithological analyses of bulk sediments,total organic carbon and granulometric analy-ses have been used to reconstruct the environmental and climatic evoluti on of the area.The ages were provided by three 14 C datings.The record suggested a climate fluctuation between warm-dry a nd cool-wet from ca.57to 32ka B.P.,which led a shallowing and swamping of the l ake.The water level again increased quickly at ca.32ka B.P.,reached it’ s peak during LGM(Last Glacial Maximum,ca.18-20ka B.P.)and remained relative high until ca.15ka B.P.The high wa-ter level at LGM is attributed to cold-wet conditions.The area experienced an abrupt and unstable climatic ch anges dur-ing the transition period from15to 10ka B.P.with a dominated littoral en vironment.Awarm-dry climate led to the contrac-tion of the lake during the Holocene a nd reed-swamps became dominant.After a minor wet-cool pulse during the L ate Holocene,the modern climate became to be established.展开更多
The degradation of forest and soil contribute significantly to carbon emission to the atmosphere leading to the build-up of carbon dioxide in atmosphere and contributing to global warming. Consequences of climate chan...The degradation of forest and soil contribute significantly to carbon emission to the atmosphere leading to the build-up of carbon dioxide in atmosphere and contributing to global warming. Consequences of climate change are not only the rise in global temperatures, but also changes in the precipitation patterns, which could affect agricultural production, food security, human health and long-term ecosystem properties balance. The deforestation and land degradation are major sources of GHG (greenhouse gas) emissions. International negotiations and dialogues on REDD+ mechanism are held for both national and local level mitigation policies formulation for the reduction of carbon emission from land use, land use change and forestry sector. The reduction of emissions from fossil fuel combustion and avoidance of deforestation and forest/land degradation constitute lasting and long-term solutions for mitigating climate change. There is an urgent need of relevant and efficient methods of measuring forest and soil carbon through application of the latest geospatial technologies, i.e., GIS (geographic information system), Remote Sensing and LiDAR (Light Detection and Ranging). These technologies can support the precise measurement of carbon stocks, as well as, offer cost effective and interoperable data generation methods. The REDD+ mechanism is being promoted worldwide mainly to reduce the diminishing of forest in developing countries. Such an approach must consider use rights, sustainable management of forests, ensuring and safe-guarding the benefit sharing mechanism and good governance, along with the legal framework and local livelihood concerns.展开更多
The PIRATA-SWE (Prediction and Research Moored Array in the Tropical Atlantic-Southwest Extension) was conceived in the early 2000s to gather observations necessary to improve the understanding of the variability of...The PIRATA-SWE (Prediction and Research Moored Array in the Tropical Atlantic-Southwest Extension) was conceived in the early 2000s to gather observations necessary to improve the understanding of the variability of ocean-atmosphere interactions in the SACZ (South Atlantic Convergence Zone), which are believed to influence South American climate. To properly monitor the SACZ, the preliminary design for the PIRATA-SWE array considered the mooring of four buoys, with the southernmost one in the sub-tropics. In 2005, three buoys were deployed in the tropical region. Four years later, in 2009, efforts were started to assemble and deploy a Brazilian prototype of the TAO/PIRATA Atlas (autonomous temperature line acquisition system) buoy-the Atlas-B. Finally, in April 2013 the first Atlas-B, nicknamed "Guariroba", was moored for a testing period at 28.5° S, 44° W, which is the site originally planned for the fourth PIRATA-SWE buoy. In early November 2013, after being detected adrift, the buoy with the upper 700 m part of the mooring line was rescued in an emergency operation. In June 2014, the bottom part was successfully recovered. A new deployment is planned for late 2014. This paper describes part of the learning process of adapting and building the Atlas-B buoy and presents a brief discussion of the data collected during the pilot deployment.展开更多
Although extensive studies have been performed on nitrogen isotopes in lake sediments, understanding the complexity of the δ15N variation related to past environmental and climatic conditions still remains unclear. S...Although extensive studies have been performed on nitrogen isotopes in lake sediments, understanding the complexity of the δ15N variation related to past environmental and climatic conditions still remains unclear. Supported by multi-proxy records including litho-units, organic carbon isotopes, ration of total organic carbon and total nitrogen, organic matter content, bulk dry density, the accumulation rate of organic matter, median grain size, magnetic susceptibility, and Rb/Sr and Ca/Mg ratios obtained from a sedimentary sequence in a small lake (i.e., Dahu Swamp) in the eastern Nanling Mountains in South China, we deduce that variation in the δ15N values results primarily from the sources of organic matter, which are significantly influenced by climatic conditions over the past -16 000 years. A low (or high) lake level resulting from dry (or wet) conditions would lead to more (or fewer) vascular plant remains in the sediments and stronger (or weaker) denitrification associated with hypolimnetic anoxia, resulting in lower (or higher) 615N values. In addition, dry (or wet) conditions would favor weakened (or strengthened) biogeochemical activity in the catchment, which could result in less (or more) external input of δ15N-enriched OM, thus leading to decreased (or increased) δ15N values. Our results indicate that the lake sediment δ15N record in the Nanling Mountains has the potential to provide valuable insight into past East Asian monsoon climate- driven environmental changes.展开更多
The weather has a significant influence on yield fluctuations in Nepal, particularly for grains. This study examined the effect of seasonal precipitation, maximum and minimum temperatures and extreme climatic variable...The weather has a significant influence on yield fluctuations in Nepal, particularly for grains. This study examined the effect of seasonal precipitation, maximum and minimum temperatures and extreme climatic variables on yield levels and variability of rice, maize and wheat yields. The authors applied a stochastic production function approach as suggested by Just-Pope for panel data at the district level. The estimation results indicated that climate trends in Nepal had a significant influence on crop yield levels and variances in various magnitudes and directions. The results showed an increase in precipitation negatively influenced maize yield levels and positively influenced wheat yield levels; however, a positive influence was found to reduce yield variability in rice and wheat. Similarly, an increase in maximum temperature apparently led to decreased maize and increased wheat yield levels, respectively, and also led to increased yield variability in rice and maize. Likewise, the minimum temperature was helpful to increase yield levels for all crops and to decrease the yield variability in rice and maize. Moreover, the extreme climates such as low precipitation and high maximum temperatures significantly influenced the reduction in yield levels of rice and maize, respectively that could be used to design an index insurance product for Nepal.展开更多
Mountain ecosystems are relatively more vulnerable to climate change since human induced climate change is projected to be higher at high altitudes and latitudes. Climate change induced effects related to glacial resp...Mountain ecosystems are relatively more vulnerable to climate change since human induced climate change is projected to be higher at high altitudes and latitudes. Climate change induced effects related to glacial response and water hazards have been documented in the Himalayas in recent years, yet studies regarding species' response to climate change are largely lacking from the mountains and Himalayas of Nepal. Changes in distribution and latitudinal/altitudinal range shift, which are primary adaptive responses to climate change in many species,are largely unknown due to unavailability of adequate data from the past. In this study, we explored the elevational distribution of butterflies in Langtang Village Development Committee(VDC) of Langtang National park; a park located in the high altitudes of Nepal. We found a decreasing species richness pattern along the elevational gradient considered here.Interestingly, elevation did not appear to have a significant effect on the altitudinal distribution ofbutterflies at family level. Also, distribution of butterflies in the area was independent of habitat type,at family level. Besides, we employed indicator group analysis(at family level) and noticed that butterfly families Papilionidae, Riodinidae, and Nymphalidae are significantly associated to high, medium and low elevational zone making them indicator butterfly family for those elevational zones, respectively. We expect that this study could serve as a baseline information for future studies regarding climate change effects and range shifts and provide avenues for further exploration of butterflies in the high altitudes of Nepal.展开更多
By using the data of 1949 – 2001 (53 years) of Tropical Cyclone (TC) Yearbooks, statistical analyses are performed to study the climatic features of TCs making landfall and then passing through lakes (hereafter refer...By using the data of 1949 – 2001 (53 years) of Tropical Cyclone (TC) Yearbooks, statistical analyses are performed to study the climatic features of TCs making landfall and then passing through lakes (hereafter referred to as "L-TCs") in China. Results show that L-TCs can sustain a long time over land and the intensity is very strong during the course of landfall. Lakes can noticeably slow down the reduction of TC intensity, with the minimum pressure mostly maintained or decreased and the maximum velocity increased. The middle reach of the Yangtze River has the biggest TC dissipating rate as compared with the other areas where the TC is active.展开更多
The total organic carbon (TOC) content series from the lake sediment of Minqin Basin (100°57′–104°57′E, 37°48′–39°17′N) in northwestern China, which has a 10 000-year-long paleo-climatic prox...The total organic carbon (TOC) content series from the lake sediment of Minqin Basin (100°57′–104°57′E, 37°48′–39°17′N) in northwestern China, which has a 10 000-year-long paleo-climatic proxy record, was used to analyze the Holocene climate changes in the local region. The proxy record was established in the Sanjiaocheng (SJC), Triangle Town in Chinese, Section (103°20′25″E, 39°00′38″N), which is located at the northwestern boundary of the present Asian summer monsoon in China, and is sensitive to global environmental and climate changes. Applying singular spectrum analysis (SSA) to the TOC series, principal climatic oscillations and periodical changes were studied. The results reveal 3 major patterns of climate change regulated by reconstructed components (RCs). The first pattern is natural long-term trend of climatic change in the local area (Minqin Basin), indicating a relatively wetter stage in early Holocene (starting at 9.5 kaBP), and a relatively dryer stage with a strong lake desiccation and a declined vegetation cover in mid-Holocene (during 7–6 kaBP). From 4.0 kaBP to the present, there has been a gradually decreasing trend in the third reconstructed component (RC3) showing that the local climate changed again into a dryer stage. The second pattern shows millennial-centennial scale oscillations containing cycles of 1 600 and 800 years that have been present throughout almost the entire Holocene period of the last 10 000 years. The third pattern is a millennial-centennial scale variation with a relatively smaller amplitude and unclear cycles showing a nonlinear interaction within the earth’s climate systems.展开更多
Lake Lop Nur is located in the eastern part of the Tarim Basin in Xinjiang,northwestern China.A 220-cm-long sediment core was collected from the center of the ear-shaped depression forming the basin and dated with AMS...Lake Lop Nur is located in the eastern part of the Tarim Basin in Xinjiang,northwestern China.A 220-cm-long sediment core was collected from the center of the ear-shaped depression forming the basin and dated with AMS^(14)C.Grain size,total organic matter(TOC),total nitrogen(TN),and TOC/TN(C/N)analyses were used to reconstruct climatic conditions from 13.0 to 5.6 cal ka BP.The results showed fi ve main climatic stages.Zone I(13.0–11.3 cal ka BP)was a wet–dry environment,whereas Zone II(11.3–8.9 cal ka BP)consisted of a primarily wet environment.Zone III(8.9–7.7 cal ka BP)was subdivided into Zone IIIa(8.9–8.2 cal ka BP)that indicated lake constriction and dry climate,and Zone IIIb(8.2–7.7 cal ka BP)in which the proxies indicated wet conditions.In Zone IV(7.7–6.6 cal ka BP),the climate presented a bit wet conditions.In Zone V(6.6–5.6 cal ka BP),abundant glauberite is present in the sediment and silt dominates the lithology;these results indicate the lake shrank and the overall climate was dry.Abrupt environmental events were also identifi ed,including six dry events at 11.0,10.5,9.3,8.6,8.2,and 7.6 cal ka BP and one fl ood event from 7.8 to 7.7 cal ka BP in the Early–Middle Holocene.展开更多
This paper presents the results of determining trace elements and δ 13C, δ 18O in Gyraulus sibirica shell continuously preserved in Xingcuo Lake sediments in the recent 50 years. By coupling these indexes and instru...This paper presents the results of determining trace elements and δ 13C, δ 18O in Gyraulus sibirica shell continuously preserved in Xingcuo Lake sediments in the recent 50 years. By coupling these indexes and instrumental meteorological data on its basin to determine the relations among them, we probed quantitatively the climatic signals recorded in Xingcuo Lake sediments. The results showed that gastropod shells in Xingcuo Lake were formed in warm seasons; that trace elements, and stable isotope in shells just recorded the climatic signals of the warm seasons instead of that of the whole year; that Mg/Ca ratio and δ 18O proxy had certain correlation with air temperature in warm seasons, when the δ 18O proxy was more sensitive; with the average ratio of them being 0.28×10 -3/℃ and the variation rate dδ 18O/dT being 1.64×10 -3/℃; that the Sr/Ca ratio and δ 13C proxy, especially Sr/Ca ratio, had close correlation; and that dSr/Ca/dP was -0.045/mm.展开更多
The paper is based on author's observations during long geological field investigations in the Nepal Himalayas and various other international researches pertaining to natural hazards, global warming and climate chan...The paper is based on author's observations during long geological field investigations in the Nepal Himalayas and various other international researches pertaining to natural hazards, global warming and climate change. High mountains all over the world including Nepal Himalaya are threatened by global warming. In addition, Nepal lies at heart of Himalayan orogenic belt and is prone to both geological and hydro-meteorological hazard. Tremendous geographic diversity from high mountains to fiat plains presents specific hazards like earthquakes, avalanche, glacial lake outburst flood, debris flow, floods, landslides, thunderstorm, fire, cold and hot waves, etc. These natural hazards combined with anthropogenic hazards aggravate and degrade the fragile eco-systems, put human lives at risk, and cause immense economic losses. In last 25 years, it has attributed to an average annual loss of about 850 lives, damage of infrastructures and properties equivalent to about 6% of the annual development expenditure. GHGs (Green House Gases) are the chief sources of global warming and climate change. In Nepal, these are marked by an average of 0.06℃ per year rise in temperature, fast snow melting, retreating glaciers, vertical shift in snowline, decrease in amount of snowfall, appearance of new glacial lakes and increase in their size and volume. There is a need of strong commitment of international community to work together to reduce GHGs, CFC (Chlorofluorocarbon), and international and regional cooperation to face the present challenges of global warming and climate change. Government of Nepal already prepared the National Strategy for Disaster Risk Management for building a resilient nation emphasizing on assessment, identification, and monitoring of disaster risk and enhancing early warning system.展开更多
Rupa Lake is small advancing eutrophic lake covering about 115 ha of the Lekhnath Municipality in Kaski district of western Nepal. The environment around the lake has been improved over a period of 10 years. Conservat...Rupa Lake is small advancing eutrophic lake covering about 115 ha of the Lekhnath Municipality in Kaski district of western Nepal. The environment around the lake has been improved over a period of 10 years. Conservation practices were initiated by communities including the Rupa Lake Restoration and Fishery Cooperative (RLRFC). As a result, an abundance of non-timber Forest Products (NTFP) has increased considerably. At present, 49 NTFP are available in the lake basin. Some households (HH) i.e 10% has additional income from NTFP. It is an indirect source of food security for local people. They sell NTFP products to generate income. A few households have already started farming of NTFPs. Availability of fodder and fuel wood from community forest has significantly contributed to the livelihoods of people where as wild edible fruits and vegetables have become supplementary for food security. There is yearly food security for 57% of HH with 22% having surplus food. 5% of HH has food security for less than three months where as 19% HHs have food security for more than six months. However, livelihood and nutritional security have improved by fish farming in lake. This lake is most important for the local environment and also helps eco-tourism. The study found that 92% observed the climate change in the form of a rise in temperature (〉 70% HHs); unpredictable rainfall (〉 75% HHs); shifting rainfall (〉 60% HHs); phonological changes (〉 50%). It showed that the lake supports the restoration of natural water capacity, maintain local climate and sound environment by better natural resource management for an environment friendly ecosystem.展开更多
Long-chain alkenones (LCAs) can potentially be used as indicators to understand past variations in lacustrine environments.Previous research has suggested that the relationship between the temperature and the unsatura...Long-chain alkenones (LCAs) can potentially be used as indicators to understand past variations in lacustrine environments.Previous research has suggested that the relationship between the temperature and the unsaturation index of LCAs should be calibrated individually,because of the possible variations in the alkenone-producing algal species in the lacustrine environment.In this work,we have calibrated U37K' of water filter samples against the in-situ water temperature in Lake Qinghai,Tibetan Plateau.There are significant relationships between U37K' and the water temperature,a non-linear relationship was derived.Because the U37K' values did not respond sensitively at lower temperatures,we suggested that a quadratic regression (U37K' =0.0011×T2-0.0201×T+0.1959,n=15,r2=0.74) was appropriate than linear regression to represent the relationship between the in-situ temperatures and U37K'.Meanwhile,the U37K correlation relationship was not more significant than U37K' index in our study.Because of the C37:4 effects by salinity change,we suggest U37K is not as robust as the U37K' index as a temperature proxy,at least for the salt lake in the Tibetan Plateau.The calibration of the U37K' index in this work has provided a new understanding of historic climatic changes in the Tibetan Plateau.展开更多
Inland lakes and alpine glaciers are important water resources on the Tibetan Plateau. Understanding their variation is crucial for accurate evaluation and prediction of changes in water supply and for retrieval and a...Inland lakes and alpine glaciers are important water resources on the Tibetan Plateau. Understanding their variation is crucial for accurate evaluation and prediction of changes in water supply and for retrieval and analysis of climatic information. Data from previous research on 35 alpine lakes on the Tibetan Plateau were used to investigate changes in lake water level and area. In terms of temporal changes, the area of the 35 alpine lakes could be divided into five groups: rising, falling-rising, rising-falling, fluctuating, and falling. In terms of spatial changes, the area of alpine lakes in the Himalayan Mountains, the Karakoram Mountains, and the Qaidam Basin tended to decrease; the area of lakes in the Naqu region and the Kunlun Mountains increased; and the area of lakes in the Hoh Xil region and Qilian Mountains fluctuated. Changes in lake water level and area were correlated with regional changes in climate. Reasons for changes in these lakes on the Tibetan Plateau were analyzed, including precipitation and evaporation from meteorological data, glacier meltwater from the Chinese glacier inventories. Several key problems, e.g. challenges of monitoring water balance, limitations to glacial area detection, uncertainties in detecting lake water-level variations and variable region boundaries of lake change types on the Tibetan Plateau were discussed. This research has most indicative significance to regional climate change.展开更多
This work presents changes of thermokarst lakes from Beilu River Basin on the Qinghai-Tibet Plateau over the past four decades (1969-2010) using aerial and satellite image interpretation. The results indicated that ...This work presents changes of thermokarst lakes from Beilu River Basin on the Qinghai-Tibet Plateau over the past four decades (1969-2010) using aerial and satellite image interpretation. The results indicated that thermokarst lake activity had generally increased rapidly between 1969 and 2010. The number of thermokarst lakes had increased by approximately 534, and their coverage expanded by about 410 ha. The two main changes observed were an increase in the number of small lakes and the expansion of larger lakes. These changes are likely the result of persistent climate warming and a gradually increasing imbalance between precipitation and evapotranspiration (PET). However, some non-climatic factors, such as the lake-bottom substrate and local engineering activities, have also influenced the lake changes. If air temperature and P-ET continue to rise, the number of thermokarst lakes and the area they cover may continue to increase in the future.展开更多
基金Under the auspices of Taikichiro Mori Memorial Research Grants of Keio University (No. 19, 2010)Doctoral Students Research Support Program of Keio University (No. 87, 2010)Academic Frontier Fund's 'Integrated Research for Community Strategic Concept by Construction and Management of Digital Asia' by Ministry of Education, Culture, Sports, Science and Technology (MEXT) (No. 04F003, 2004-2008)
文摘The detection of glacial lake change in the Himalayas, Nepal is extremely significant since the glacial lake change is one of the crucial indicators of global climate change in this area, where is the most sensitive area of the global climate changes. In the Hima- layas, some of glacial lakes are covered by the dark mountains' shadow because of their location. Therefore, these lakes can not be de- tected by conventional method such as Normalized Difference Water Index (NDWI), because the reflectance feature of shadowed glacial lake is different comparing to the ones which are located in the open flat area. The shadow causes two major problems: 1) glacial lakes which are covered by shadow completely result in underestimation of the number of glacial lakes; 2) glacial lakes which are partly iden- tified are considered to undervalue the area of glacial lakes. The aim of this study is to develop a new model, named Detection of Shadowed Glacial Lakes (DSGL) model, to identify glacial lakes under the shadow environment by using Advanced Space-borne Ther- mal Emission and Reflection Radiometer (ASTER) data in the Himalayas, Nepal. The DSGL model is based on integration of two dif- ferent modifications of NDWI, namely NDWls model and NDWIshe model. NDWI~ is defined as integration of the NDWI and slope analysis and used for detecting non-shadowed lake in the mountain area. The NDWIshe is proposed as a new methodology to overcome the weakness of NDWI~ on identifying shadowed lakes in highly elevated mountainous area such as the Himalayas. The first step of the NDWIshe is to enhance the data from ASTER 1B using the histogram equalization (HE) method, and its outcome product is named AS- TERho. We used the ASTERhe for calculating the NDWIhc and the NDWIshe. Integrated with terrain analysis using Digital Elevation Model (DEM) data, the NDWIshe can be used to identify the shadowed glacial lakes in the Himalayas. NDWIs value of 0.41 is used to identify the glacier lake (NDWI~ 〉 0.41), and 0.3 of NDWIshe is used to identify the shadowed glacier lake (NDWIsho 〈 0.3). The DSGL model was proved to be able to classify the glacial lakes more accurately, while the NDWI model had tendency to underestimate the presence of actual glacial lakes. Correct classification rate regarding the products from NDWI model and DSGL model were 57% and 99%, respectively. The results of this paper demonstrated that the DSGL model is promising to detect glacial lakes in the shadowed en- vironment at high mountains.
基金Under the auspices of National Natural Science Foundation of China (No. 49761007)Open Foundation of National Laboratory of Western China’s Environmental Systems,Lanzhou University
文摘Study results in this paper have indicated that the Holocene climate in Xinjiang, Northwestem China has been alternating between wet and dry conditions, and was punctuated with a series of abrupt climate shifts. A sediment core taken from Barkol Lake in the northern Xinjiang of Northwest China was analyzed at 1 cm interval for grain-size distribution. Abrupt climate shifts revealed by the grain-size proxy occurred at ca 1.4, 3.0, 4.3, 5.6, 8.0 cal kyr B.E, which were well correlated to both the abrupt shifts recorded in the North Atlantic Ocean (NAO) and the Holocene sea surface temperature (SST) cooling events in the Arabian Ocean. The correlation indicated that the climatic changes in the extreme arid Northwest China were associated with the NAO, probably via the North Atlantic Oscillation-affected westerly winds. The strength and position of westerly winds probably modulated the Siberian-Mongolian high- pressure system (winter monsoon), and played an important role in climate change of Northwest China. Moreover, an evident drought interval during the middle Holocene was also revealed by grain-size proxy.
基金Under the auspices of National Natural Science Foundation of China (No. 40603007)
文摘Traditionally, the mid-Holocene in most parts of China was thought to be warmer with higher precipitation, resulting from a strong Asian summer monsoon. However, some recent researches have proposed a mid-Holocene drought interval of millennial-scale in East Asian monsoon margin areas. Thus whether mid-Holocene was dry or humid remains an open issue. Here, Zhuyeze palaeolake, the terminal lake of the Shiyang River Drainage lying in Asian monsoon marginal areas, was selected for reconstructing the details of climate variations during the Holocene, especially mid-Holocene, on the basis of a sedimentological analysis. Qingtu Lake (QTL) section of 6.92m depth was taken from Zhuyeze palaeolake. Multi-proxy analysis of QTL section, including grain size, carbonate, TOC, C/N and δ13C of organic matter, was used to document regional climatic changes during 9-3 cal ka B.P. The record shows a major environmental change at 9.0-7.8 cal ka B.P., attributed to a climate trend towards warmth and humidity. This event was followed by a typical regional drought event which occurred during 7.8-7.5 cal ka B.P. And a warm and humid climate prevailed from 7.5 to 5.0 cal ka B.P., attributed to the warm/humid Holocene Optimum in this region. After that, the climate gradually became drier. Moreover, comparison of the climate record from this paper with the summer insolation at 30°N indicates that the climate pattern reflecting the Asian monsoon changes was caused by insolation change.
文摘Information on the palaeoenvironm ent from Late Pleistocene to Holocen e in northwestern Yannan Plateau has been deduced from a study of a 28.81m-long core taken from Napahai Lake.The results from Relative Brightness In-dex(RBI )as well as those from the lithological analyses of bulk sediments,total organic carbon and granulometric analy-ses have been used to reconstruct the environmental and climatic evoluti on of the area.The ages were provided by three 14 C datings.The record suggested a climate fluctuation between warm-dry a nd cool-wet from ca.57to 32ka B.P.,which led a shallowing and swamping of the l ake.The water level again increased quickly at ca.32ka B.P.,reached it’ s peak during LGM(Last Glacial Maximum,ca.18-20ka B.P.)and remained relative high until ca.15ka B.P.The high wa-ter level at LGM is attributed to cold-wet conditions.The area experienced an abrupt and unstable climatic ch anges dur-ing the transition period from15to 10ka B.P.with a dominated littoral en vironment.Awarm-dry climate led to the contrac-tion of the lake during the Holocene a nd reed-swamps became dominant.After a minor wet-cool pulse during the L ate Holocene,the modern climate became to be established.
文摘The degradation of forest and soil contribute significantly to carbon emission to the atmosphere leading to the build-up of carbon dioxide in atmosphere and contributing to global warming. Consequences of climate change are not only the rise in global temperatures, but also changes in the precipitation patterns, which could affect agricultural production, food security, human health and long-term ecosystem properties balance. The deforestation and land degradation are major sources of GHG (greenhouse gas) emissions. International negotiations and dialogues on REDD+ mechanism are held for both national and local level mitigation policies formulation for the reduction of carbon emission from land use, land use change and forestry sector. The reduction of emissions from fossil fuel combustion and avoidance of deforestation and forest/land degradation constitute lasting and long-term solutions for mitigating climate change. There is an urgent need of relevant and efficient methods of measuring forest and soil carbon through application of the latest geospatial technologies, i.e., GIS (geographic information system), Remote Sensing and LiDAR (Light Detection and Ranging). These technologies can support the precise measurement of carbon stocks, as well as, offer cost effective and interoperable data generation methods. The REDD+ mechanism is being promoted worldwide mainly to reduce the diminishing of forest in developing countries. Such an approach must consider use rights, sustainable management of forests, ensuring and safe-guarding the benefit sharing mechanism and good governance, along with the legal framework and local livelihood concerns.
文摘The PIRATA-SWE (Prediction and Research Moored Array in the Tropical Atlantic-Southwest Extension) was conceived in the early 2000s to gather observations necessary to improve the understanding of the variability of ocean-atmosphere interactions in the SACZ (South Atlantic Convergence Zone), which are believed to influence South American climate. To properly monitor the SACZ, the preliminary design for the PIRATA-SWE array considered the mooring of four buoys, with the southernmost one in the sub-tropics. In 2005, three buoys were deployed in the tropical region. Four years later, in 2009, efforts were started to assemble and deploy a Brazilian prototype of the TAO/PIRATA Atlas (autonomous temperature line acquisition system) buoy-the Atlas-B. Finally, in April 2013 the first Atlas-B, nicknamed "Guariroba", was moored for a testing period at 28.5° S, 44° W, which is the site originally planned for the fourth PIRATA-SWE buoy. In early November 2013, after being detected adrift, the buoy with the upper 700 m part of the mooring line was rescued in an emergency operation. In June 2014, the bottom part was successfully recovered. A new deployment is planned for late 2014. This paper describes part of the learning process of adapting and building the Atlas-B buoy and presents a brief discussion of the data collected during the pilot deployment.
基金Supported by the National Natural Science Foundation of China(Nos.41071137,40671189)the Research Program of Higher Education Institution in Guangdong Province for High-level Talents,and the Natural Science Foundation of Guangdong Province(Nos.S2011010003413,8151063101000044)
文摘Although extensive studies have been performed on nitrogen isotopes in lake sediments, understanding the complexity of the δ15N variation related to past environmental and climatic conditions still remains unclear. Supported by multi-proxy records including litho-units, organic carbon isotopes, ration of total organic carbon and total nitrogen, organic matter content, bulk dry density, the accumulation rate of organic matter, median grain size, magnetic susceptibility, and Rb/Sr and Ca/Mg ratios obtained from a sedimentary sequence in a small lake (i.e., Dahu Swamp) in the eastern Nanling Mountains in South China, we deduce that variation in the δ15N values results primarily from the sources of organic matter, which are significantly influenced by climatic conditions over the past -16 000 years. A low (or high) lake level resulting from dry (or wet) conditions would lead to more (or fewer) vascular plant remains in the sediments and stronger (or weaker) denitrification associated with hypolimnetic anoxia, resulting in lower (or higher) 615N values. In addition, dry (or wet) conditions would favor weakened (or strengthened) biogeochemical activity in the catchment, which could result in less (or more) external input of δ15N-enriched OM, thus leading to decreased (or increased) δ15N values. Our results indicate that the lake sediment δ15N record in the Nanling Mountains has the potential to provide valuable insight into past East Asian monsoon climate- driven environmental changes.
文摘The weather has a significant influence on yield fluctuations in Nepal, particularly for grains. This study examined the effect of seasonal precipitation, maximum and minimum temperatures and extreme climatic variables on yield levels and variability of rice, maize and wheat yields. The authors applied a stochastic production function approach as suggested by Just-Pope for panel data at the district level. The estimation results indicated that climate trends in Nepal had a significant influence on crop yield levels and variances in various magnitudes and directions. The results showed an increase in precipitation negatively influenced maize yield levels and positively influenced wheat yield levels; however, a positive influence was found to reduce yield variability in rice and wheat. Similarly, an increase in maximum temperature apparently led to decreased maize and increased wheat yield levels, respectively, and also led to increased yield variability in rice and maize. Likewise, the minimum temperature was helpful to increase yield levels for all crops and to decrease the yield variability in rice and maize. Moreover, the extreme climates such as low precipitation and high maximum temperatures significantly influenced the reduction in yield levels of rice and maize, respectively that could be used to design an index insurance product for Nepal.
基金funded by The Rufford Foundation(http://www.rufford.org/)
文摘Mountain ecosystems are relatively more vulnerable to climate change since human induced climate change is projected to be higher at high altitudes and latitudes. Climate change induced effects related to glacial response and water hazards have been documented in the Himalayas in recent years, yet studies regarding species' response to climate change are largely lacking from the mountains and Himalayas of Nepal. Changes in distribution and latitudinal/altitudinal range shift, which are primary adaptive responses to climate change in many species,are largely unknown due to unavailability of adequate data from the past. In this study, we explored the elevational distribution of butterflies in Langtang Village Development Committee(VDC) of Langtang National park; a park located in the high altitudes of Nepal. We found a decreasing species richness pattern along the elevational gradient considered here.Interestingly, elevation did not appear to have a significant effect on the altitudinal distribution ofbutterflies at family level. Also, distribution of butterflies in the area was independent of habitat type,at family level. Besides, we employed indicator group analysis(at family level) and noticed that butterfly families Papilionidae, Riodinidae, and Nymphalidae are significantly associated to high, medium and low elevational zone making them indicator butterfly family for those elevational zones, respectively. We expect that this study could serve as a baseline information for future studies regarding climate change effects and range shifts and provide avenues for further exploration of butterflies in the high altitudes of Nepal.
基金Open Foundation for Wuhan Institute of Heavy Rain, CMA (IHR2006G09)a Natural Science Foundation of China project (40575029)
文摘By using the data of 1949 – 2001 (53 years) of Tropical Cyclone (TC) Yearbooks, statistical analyses are performed to study the climatic features of TCs making landfall and then passing through lakes (hereafter referred to as "L-TCs") in China. Results show that L-TCs can sustain a long time over land and the intensity is very strong during the course of landfall. Lakes can noticeably slow down the reduction of TC intensity, with the minimum pressure mostly maintained or decreased and the maximum velocity increased. The middle reach of the Yangtze River has the biggest TC dissipating rate as compared with the other areas where the TC is active.
基金the National Natural Science Foundation of China (NSFC) (No. 40571169)the NSFC’s Innovation Team Project (No. 40421101), and the NSFC’s Key Program Project (No. 90502008)
文摘The total organic carbon (TOC) content series from the lake sediment of Minqin Basin (100°57′–104°57′E, 37°48′–39°17′N) in northwestern China, which has a 10 000-year-long paleo-climatic proxy record, was used to analyze the Holocene climate changes in the local region. The proxy record was established in the Sanjiaocheng (SJC), Triangle Town in Chinese, Section (103°20′25″E, 39°00′38″N), which is located at the northwestern boundary of the present Asian summer monsoon in China, and is sensitive to global environmental and climate changes. Applying singular spectrum analysis (SSA) to the TOC series, principal climatic oscillations and periodical changes were studied. The results reveal 3 major patterns of climate change regulated by reconstructed components (RCs). The first pattern is natural long-term trend of climatic change in the local area (Minqin Basin), indicating a relatively wetter stage in early Holocene (starting at 9.5 kaBP), and a relatively dryer stage with a strong lake desiccation and a declined vegetation cover in mid-Holocene (during 7–6 kaBP). From 4.0 kaBP to the present, there has been a gradually decreasing trend in the third reconstructed component (RC3) showing that the local climate changed again into a dryer stage. The second pattern shows millennial-centennial scale oscillations containing cycles of 1 600 and 800 years that have been present throughout almost the entire Holocene period of the last 10 000 years. The third pattern is a millennial-centennial scale variation with a relatively smaller amplitude and unclear cycles showing a nonlinear interaction within the earth’s climate systems.
基金Supported by the National Natural Science Foundation of China(No.41271205)the PhD Research Startup Foundation of Heibei GEO Univerity(No.BQ201604)
文摘Lake Lop Nur is located in the eastern part of the Tarim Basin in Xinjiang,northwestern China.A 220-cm-long sediment core was collected from the center of the ear-shaped depression forming the basin and dated with AMS^(14)C.Grain size,total organic matter(TOC),total nitrogen(TN),and TOC/TN(C/N)analyses were used to reconstruct climatic conditions from 13.0 to 5.6 cal ka BP.The results showed fi ve main climatic stages.Zone I(13.0–11.3 cal ka BP)was a wet–dry environment,whereas Zone II(11.3–8.9 cal ka BP)consisted of a primarily wet environment.Zone III(8.9–7.7 cal ka BP)was subdivided into Zone IIIa(8.9–8.2 cal ka BP)that indicated lake constriction and dry climate,and Zone IIIb(8.2–7.7 cal ka BP)in which the proxies indicated wet conditions.In Zone IV(7.7–6.6 cal ka BP),the climate presented a bit wet conditions.In Zone V(6.6–5.6 cal ka BP),abundant glauberite is present in the sediment and silt dominates the lithology;these results indicate the lake shrank and the overall climate was dry.Abrupt environmental events were also identifi ed,including six dry events at 11.0,10.5,9.3,8.6,8.2,and 7.6 cal ka BP and one fl ood event from 7.8 to 7.7 cal ka BP in the Early–Middle Holocene.
文摘This paper presents the results of determining trace elements and δ 13C, δ 18O in Gyraulus sibirica shell continuously preserved in Xingcuo Lake sediments in the recent 50 years. By coupling these indexes and instrumental meteorological data on its basin to determine the relations among them, we probed quantitatively the climatic signals recorded in Xingcuo Lake sediments. The results showed that gastropod shells in Xingcuo Lake were formed in warm seasons; that trace elements, and stable isotope in shells just recorded the climatic signals of the warm seasons instead of that of the whole year; that Mg/Ca ratio and δ 18O proxy had certain correlation with air temperature in warm seasons, when the δ 18O proxy was more sensitive; with the average ratio of them being 0.28×10 -3/℃ and the variation rate dδ 18O/dT being 1.64×10 -3/℃; that the Sr/Ca ratio and δ 13C proxy, especially Sr/Ca ratio, had close correlation; and that dSr/Ca/dP was -0.045/mm.
文摘The paper is based on author's observations during long geological field investigations in the Nepal Himalayas and various other international researches pertaining to natural hazards, global warming and climate change. High mountains all over the world including Nepal Himalaya are threatened by global warming. In addition, Nepal lies at heart of Himalayan orogenic belt and is prone to both geological and hydro-meteorological hazard. Tremendous geographic diversity from high mountains to fiat plains presents specific hazards like earthquakes, avalanche, glacial lake outburst flood, debris flow, floods, landslides, thunderstorm, fire, cold and hot waves, etc. These natural hazards combined with anthropogenic hazards aggravate and degrade the fragile eco-systems, put human lives at risk, and cause immense economic losses. In last 25 years, it has attributed to an average annual loss of about 850 lives, damage of infrastructures and properties equivalent to about 6% of the annual development expenditure. GHGs (Green House Gases) are the chief sources of global warming and climate change. In Nepal, these are marked by an average of 0.06℃ per year rise in temperature, fast snow melting, retreating glaciers, vertical shift in snowline, decrease in amount of snowfall, appearance of new glacial lakes and increase in their size and volume. There is a need of strong commitment of international community to work together to reduce GHGs, CFC (Chlorofluorocarbon), and international and regional cooperation to face the present challenges of global warming and climate change. Government of Nepal already prepared the National Strategy for Disaster Risk Management for building a resilient nation emphasizing on assessment, identification, and monitoring of disaster risk and enhancing early warning system.
文摘Rupa Lake is small advancing eutrophic lake covering about 115 ha of the Lekhnath Municipality in Kaski district of western Nepal. The environment around the lake has been improved over a period of 10 years. Conservation practices were initiated by communities including the Rupa Lake Restoration and Fishery Cooperative (RLRFC). As a result, an abundance of non-timber Forest Products (NTFP) has increased considerably. At present, 49 NTFP are available in the lake basin. Some households (HH) i.e 10% has additional income from NTFP. It is an indirect source of food security for local people. They sell NTFP products to generate income. A few households have already started farming of NTFPs. Availability of fodder and fuel wood from community forest has significantly contributed to the livelihoods of people where as wild edible fruits and vegetables have become supplementary for food security. There is yearly food security for 57% of HH with 22% having surplus food. 5% of HH has food security for less than three months where as 19% HHs have food security for more than six months. However, livelihood and nutritional security have improved by fish farming in lake. This lake is most important for the local environment and also helps eco-tourism. The study found that 92% observed the climate change in the form of a rise in temperature (〉 70% HHs); unpredictable rainfall (〉 75% HHs); shifting rainfall (〉 60% HHs); phonological changes (〉 50%). It showed that the lake supports the restoration of natural water capacity, maintain local climate and sound environment by better natural resource management for an environment friendly ecosystem.
基金supported by the National Natural Science Foundation of China(41002059)the West Light Foundation of the Chinese Academy of Sciences
文摘Long-chain alkenones (LCAs) can potentially be used as indicators to understand past variations in lacustrine environments.Previous research has suggested that the relationship between the temperature and the unsaturation index of LCAs should be calibrated individually,because of the possible variations in the alkenone-producing algal species in the lacustrine environment.In this work,we have calibrated U37K' of water filter samples against the in-situ water temperature in Lake Qinghai,Tibetan Plateau.There are significant relationships between U37K' and the water temperature,a non-linear relationship was derived.Because the U37K' values did not respond sensitively at lower temperatures,we suggested that a quadratic regression (U37K' =0.0011×T2-0.0201×T+0.1959,n=15,r2=0.74) was appropriate than linear regression to represent the relationship between the in-situ temperatures and U37K'.Meanwhile,the U37K correlation relationship was not more significant than U37K' index in our study.Because of the C37:4 effects by salinity change,we suggest U37K is not as robust as the U37K' index as a temperature proxy,at least for the salt lake in the Tibetan Plateau.The calibration of the U37K' index in this work has provided a new understanding of historic climatic changes in the Tibetan Plateau.
基金The Major State Basic Research Development of China,No.2015CB954101National Mountain Flood Disaster Investigation Project,No.SHZH-IWHR-57+2 种基金The National Science and Technology Basic Special Project,No.2011FY11040-2National Natural Science Foundation of China,No.41171332The Surveying and Mapping Geoinformation Nonprofit Specific Project,No.201512033
文摘Inland lakes and alpine glaciers are important water resources on the Tibetan Plateau. Understanding their variation is crucial for accurate evaluation and prediction of changes in water supply and for retrieval and analysis of climatic information. Data from previous research on 35 alpine lakes on the Tibetan Plateau were used to investigate changes in lake water level and area. In terms of temporal changes, the area of the 35 alpine lakes could be divided into five groups: rising, falling-rising, rising-falling, fluctuating, and falling. In terms of spatial changes, the area of alpine lakes in the Himalayan Mountains, the Karakoram Mountains, and the Qaidam Basin tended to decrease; the area of lakes in the Naqu region and the Kunlun Mountains increased; and the area of lakes in the Hoh Xil region and Qilian Mountains fluctuated. Changes in lake water level and area were correlated with regional changes in climate. Reasons for changes in these lakes on the Tibetan Plateau were analyzed, including precipitation and evaporation from meteorological data, glacier meltwater from the Chinese glacier inventories. Several key problems, e.g. challenges of monitoring water balance, limitations to glacial area detection, uncertainties in detecting lake water-level variations and variable region boundaries of lake change types on the Tibetan Plateau were discussed. This research has most indicative significance to regional climate change.
基金supported by the National Basic Research Program of China (2012CB026101)the Western Project Program of the Chinese Academy of Sciences (KZCX2-XB3-19)the National Sci-Tech Support Plan (2014BAG05B01)
文摘This work presents changes of thermokarst lakes from Beilu River Basin on the Qinghai-Tibet Plateau over the past four decades (1969-2010) using aerial and satellite image interpretation. The results indicated that thermokarst lake activity had generally increased rapidly between 1969 and 2010. The number of thermokarst lakes had increased by approximately 534, and their coverage expanded by about 410 ha. The two main changes observed were an increase in the number of small lakes and the expansion of larger lakes. These changes are likely the result of persistent climate warming and a gradually increasing imbalance between precipitation and evapotranspiration (PET). However, some non-climatic factors, such as the lake-bottom substrate and local engineering activities, have also influenced the lake changes. If air temperature and P-ET continue to rise, the number of thermokarst lakes and the area they cover may continue to increase in the future.