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Both central-eastern U.S. and China are prone to increasing flooding from Mississippi River and Yangtze River basins respectively. This paper contrasts historical and projected spatialtemporal distribution of extreme precipitation in these two large river basins using 31 CMIP5 (coupled model intercomparison project phase 5) models' historical and RCP8.5 (representative concentration pathway) experiments. Results show that (1) over both river basins, the heaviest rainfall events have increased in recent decades while the lightest precipitation reduced in frequency. Over Mississippi River Basin, both the lightest precipitation (<2.5 mm/day) and heaviest (>50 mm/day) would decrease in frequency notably after mid-2020s while intermediate events occur more frequently in future; whereas over the Yangtze River Basin, all categories of precipitation are projected to increase in frequency over the coming decades. (2) Although the consensus of CMIP5 models was able to reproduce well domain-time mean and even time-averaged spatial distribution of precipitation, they failed to simulate precipitation trends both in spatial distribution and time means. In a similar fashion, models captured well statistics of precipitation but they had difficulty in representing temporal variations of different precipitation intensity categories. (3) The well-documented 2nd half of the 20th century surface summer cooling over the two river basins showed different associations with precipitation trends with higher anti-correlation between them over the U.S. region, implying different processes contributing to the cooling mechanisms of the two river basins. [ABSTRACT FROM AUTHOR]

Based on the historical documents and measured data from the active-layer temperature (ALT) at A, B and C locations (4 670, 4 720 and 4 770 m a.s.l.) on Baishui Glacier No. 1, southeastern Tibetan Plateau, this paper analyzed spatial-temporal characteristics of ALT and its relationship with air temperature, and revealed the response of the active layer ice temperature towards climate change in the monitoring period. The results showed that the influence of air temperature on the active-layer ice temperature had a hysteresis characteristic on the upper of ablation zone and the lag period increased gradually with the altitude elevating. The decrease amplitude of ALT in the accumulation period was far below its increase magnitude in the ablation period. At the same time, the mean glacier ice temperatures at 10 m depth ( T) in A, B and C profile were obviously higher than most of glaciers previously studied. Measured data also showed that the mean ALT increased by 0.24 °C in 0.5-8.5 m depth of the C profile during 28 years from July 11, 1982 to July 10, 2009. [ABSTRACT FROM AUTHOR]

In this article, we review the current knowledge of the glacial recession and related glacial lake development in the Andes of South America. Since the mid-1980s, hundreds of glacial lakes either expanded or formed, and predictions show that additional hundreds of lakes will form throughout the 21st century. However, studies on glacial lakes in the Andes are still relatively rare. Many glacial lakes pose a potential hazard to local communities, but glacial lake outburst floods (GLOFs) are understudied. We provide an overview on hazards from glacial lakes such as GLOFs and water pollution, and their monitoring approaches. In real-time monitoring, the use of unmanned aerial systems (UASs) and early warning systems (EWSs) is still extremely rare in the Andes, but increasingly authorities plan to install mitigation systems to reduce glacial lake risk and protect local communities. In support, we propose an international remote sensing-based observation initiative following the model of, for example, the Global Land Ice Measurements from Space (GLIMS) one, with the headquarters in one of the Andean nations. [ABSTRACT FROM AUTHOR]

Despite several regional glacier and glacier lake inventories, the relationship between receding glacier, glacial lake evolution (glacial-lake interactions) and their sensitivity to different forcing factors have not been properly understood yet. To better understand these processes, we used satellite images collected in 1994, 2015 and 2017 to monitor the spatially-explicit evolution of glacial lakes and glacier changes. The results show a total of 1 353 glacial lakes covering an area of 7.96 km2 in the year 2015. Out of these, a total of 137 glacial lakes having an area of >0.01 km2 and located within 2 km periphery of mother glacier have been selected for the monitoring of spatial development between 1994 and 2017. We found an increase in the total lake area from ∼4.9 to ∼7.73 km2 between 1994 and 2017, corresponding to an overall expansion of ∼57%. The total area covered by the glaciers associated with these lakes reduced from ∼365 km2 in 1994 to ∼358 km2 in 2017, accounting for a glacier loss of ∼7 km2 and corresponding to ∼1.92% reduction. Our study results are in agreement with global glacier behavior, revealing a rapid glacier recession and accelerated glacial lake expansion under an unprecedented climate change scenario. In addition, the results suggest a significant reduction in the glacier area and a close relationship between the glacier melting and lake changes. [ABSTRACT FROM AUTHOR]

The last millennium climate reconstructions are complex and limit our understanding of the mechanisms behind environmental and climate variability. We present multi-proxy centennial-scale records from the Cherai, southwest India. The last 2000 cal yr AD record suggests a complex environmental condition that prevailed at the depositional site augmenting the role of natural as well as anthropogenic agents. Increased elemental variations and indices values indicate stronger weathering, presumably wetter conditions and intense precipitation. Provenance studies suggest diverse sources and the main composition fall close to the Charnockite and Gneissic composition. Multi-proxy data suggests that a shift towards wetter climatic conditions, which occurred from 910 to 1230 cal yr AD. The core also records a shift towards the drier conditions that started around 1230 cal yr AD with a loss in vegetation diversity. The pollution load index values suggest that the overall study area falls in moderate contamination levels, which are also substantiated with the diatom data indicating human influence in the natural habitat during the deposition time. The present study reveals that the enhanced Cd and As concentration is due to strong anthropogenic influence. We compared the multi-proxy record with other continental and marine palaeoclimatic records to explore global and/or regional trends in climate variability during the last 2000 years. [ABSTRACT FROM AUTHOR]

From a large number of case studies on terrestrial deposits we know that Late Holocene climate fluctuations have an important impact on the terrestrial environments. However, it is hitherto not clear how the marine sediments can be used to shed light on the environment and climate change of the catchment. To provide such insight, we used the major element, trace element and rare earth element (REE) compositions in the southern Yellow Sea (SYS) sediments to reconstruct the changes in weathering and erosion of their source regions. The sediments originate predominantly from the upper crust of East China and are transported into the basin especially by the Yellow River (Huanghe) and to a lesser extent by the Yangtze River (Changjiang). The chemical index of alteration (CIA; 53.7-59.7) suggests low chemical weathering of the source rocks since the Middle Holocene. This is consistent with the relatively cool and arid climate in North China after the Holocene Megathermal. Comparison of element ratios, including Al/Ca, K/Ca, Al/Na, K/Na, Rb/Sr, Li/Ba and the CIA shows that we can use the latter as a robust proxy for climate change. The CIA-based mean annual precipitation and mean annual temperature show a series of climate fluctuations in the catchment. A relatively warm and humid Period I (5.3-2.9 cal. ka BP), a relatively cool and dry Period II (2.9-0.9 cal. ka BP) and an increasingly cool and dry Period III (0.9-0.3 cal. ka BP). These periods can be linked to climate intervals recognized elsewhere. [ABSTRACT FROM AUTHOR]

Copula-based bivariate frequency analysis can be used to investigate the changes in flood characteristics in the Huai River Basin that could be caused by climate change. The univariate distributions of historical flood peak, maximum 3-day and 7-day volumes in 1961-2000 and future values in 2061-2100 projected from two GCMs (CSIRO-MK3.5 and CCCma-CGCM3.1) under A2, A1B and B1 emission scenarios are analyzed and compared. Then, bivariate distributions of peaks and volumes are constructed based on the copula method and possible changes in joint return periods are characterized. Results indicate that the Clayton copula is more appropriate for historical and CCCma-CGCM3.1 simulating flood variables, while that of Frank and Gumbel are better fitted to CSIRO-MK3.5 simulations. The variations of univariate and bivariate return periods reveal that flood characteristics may be more sensitive to different GCMs than different emission scenarios. Between the two GCMs, CSIRO-MK3.5 evidently predicts much more severe flood conditions in future, especially under B1 scenario, whereas CCCma-CGCM3.1 generally suggests contrary changing signals. This study corroborates that copulas can serve as a viable and flexible tool to connect univariate marginal distributions of flood variables and quantify the associated risks, which may provide useful information for risk-based flood control. [ABSTRACT FROM AUTHOR]

The North China Plain (NCP) is one of the water shortage areas of China. Lack of water resources restricted the economic and social development of North China area and resulted in deterioration of ecosystem and natural environment. Influenced by the climate change and human activities, the water circulation of NCP was largely changed and the crisis of water resources was aggravated. Therefore, it is important to study the features of the extreme climate and the response mechanism of groundwater to climate change. We analyzed the trend of climate change and extreme climate features in the past 60 years based on the monitoring data of meteorological stations. And then the response characteristics of groundwater to climate change were discussed. The average temperature of NCP was in an obviously upward trend. The overall precipitation variation was in a downward trend. The climate change in this area showed a warming-drying trend. The intensity of extreme precipitation displayed a trend of declining and then increasing from north to south as well as declining from eastern coastal plain to the piedmont plain. Grey correlation degree analysis indicated that groundwater depth had a close relationship with precipitation and human activities in NCP. The response of groundwater level to precipitation differed from the piedmont alluvial-pluvial plain to the coastal plain. The response was more obvious in the coastal plain than the piedmont alluvial-pluvial plain and the middle plain. The precipitation influenced the groundwater depth both directly and indirectly. Under the condition of extreme precipitation, the impact would aggravate, in the forms of rapid or lag raise of groundwater levels. [ABSTRACT FROM AUTHOR]

A total of 80 weathering pits (gnammas), located on granite surfaces of Qing Mountain (青山), Hexigten (克什克腾) Global Geopark, Inner Mongolia, were identified and measured in terms of dimensional and orientational features. This article attempts to extract characteristics of the weathering pits by descriptive statistics and orientation rose diagrams, investigate the multi-phase evolution by the modified gnamma morphological analysis (GMA) method, and shed new light on the possible genesis and the influencing factors. Following the modified GMA method, weathering pits in Qing Mountain have been divided into six groups and compared with analogous sites to deduce their approximate age, which might be no older than 30 ka B.P., and explore the possibility that the multi-phase evolution of weathering pits may arise from responses to climate change. In consequence, we suggest that the combination of weathering, especially salt weathering, and wind erosion, both of which are closely related to climatic variation, take the main responsibility for the formation and development of weathering pits in Qing Mountain. [ABSTRACT FROM AUTHOR]

Water pollution is among the most severe environmental problems in China, particularly in the vicinity of residential and urban areas. In almost all Asian countries, river monitoring is predominantly based on the analysis of chemical data. However, biological data are a worthwhile addition for the determination of the long-term ecological status of rivers and are particularly well-suited in case of steep pollution and disturbance gradients. A tool for river water quality assessment using benthic invertebrates has been developed for selected tributaries of the middle reach of the Yangtze River. Site selection was supported by a preclassification considering physico-chemical and hydromorphological conditions. Following a stratified sampling design, 34 samples were taken in small and large streams in the subtropical mountainous area of western Hubei (湖北) (China) covering a pollution gradient, accompanied by an extensive field protocol on stream characteristics and (physico-) chemical water analyses. The proposed assessment system is computed as an average score per taxon. The challenge to further consider the additional impact from global change into the development of such tools is discussed. [ABSTRACT FROM AUTHOR]