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361.
Tracing glacier wastage in the Northern Tien Shan (Kyrgyzstan/Central Asia) over the last 40 years 总被引:2,自引:1,他引:1
Peter Niederer Viktor Bilenko Natasha Ershova Hans Hurni Sergeji Yerokhin Daniel Maselli 《Climatic change》2008,86(1-2):227-234
The status and dynamics of glaciers are crucial for agriculture in semiarid parts of Central Asia, since river flow is characterized
by major runoff in spring and summer, supplied by glacier- and snowmelt. Ideally, this coincides with the critical period
of water demand for irrigation. The present study shows a clear trend in glacier retreat between 1963 and 2000 in the Sokoluk
watershed, a catchment of the Northern Tien Shan mountain range in Kyrgyzstan. The overall area loss of 28% observed for the
period 1963–2000, and a clear acceleration of wastage since the 1980s, correlate with the results of previous studies in other
regions of the Tien Shan as well as the Alps. In particular, glaciers smaller than 0.5 km2 have exhibited this phenomenon most starkly. While they registered a medium decrease of only 9.1% for 1963–1986, they lost
41.5% of their surface area between 1986 and 2000. Furthermore, a general increase in the minimum glacier elevation of 78 m
has been observed over the last three decades. This corresponds to about one-third of the entire retreat of the minimum glacier
elevation in the Northern Tien Shan since the Little Ice Age maximum. 相似文献
362.
Phenological data have shown an increase of ca. 10 days in European growing season length in the latter part of the twentieth
century. In general, these changes have been associated with global warming. Here we present a study of thermal growing season
(GS) trends in the Greater Baltic Area, northern Europe. Yearly dates for the start, end and length of the GS were computed
for 49 stations in the studied area, using daily mean temperature measurements. Trends and tendencies of the GS parameters
were analysed within the twentieth century. We also examined GS trends in long records (starting before 1850) from the region.
The results show a general increase of the length of the GS of ca one week since 1951 in the area, where the most considerable
change has occurred in spring (starting ∼6 days earlier). The largest increases were found at stations adjacent to the Baltic
Sea and North Sea, where some Danish stations showed significant increasing trends in the length of the GS of more than 20 days.
The only tendency for a shorter GS was found in Archangelsk, north western Russia. The three longest records displayed large
inter-annual and decadal variability, with tendencies for increased frequencies of longer growing seasons since the 1950s. 相似文献
363.
River discharge and freshwater runoff to the Barents Sea under present and future climate conditions
River discharge forms a major freshwater input into the Arctic Ocean, and as such it has the potential to influence the oceanic
circulation. As the hydrology of Arctic river basins is dominated by cryospheric processes such as snow accumulation and snowmelt,
it may also be highly sensitive to a change in climate. Estimating the water balance of these river basins is therefore important,
but it is complicated by the sparseness of observations and the large uncertainties related to the measurement of snowfalls.
This study aims at simulating the water balance of the Barents Sea drainage basin in Northern Europe under present and future
climate conditions. We used a regional climate model to drive a large-scale hydrological model of the area. Using simulated
precipitation derived from a climate model led to an overestimation of the annual discharge in most river basins, but not
in all. Under the B2 scenario of climate change, the model simulated a 25% increase in freshwater runoff, which is proportionally
larger than the projected precipitation increase. As the snow season is 30–50 day shorter, the spring discharge peak is shifted
by about 2–3 weeks, but the hydrological regime of the rivers remains dominated by snowmelt. 相似文献
364.
365.
LINET—An international lightning detection network in Europe 总被引:1,自引:0,他引:1
Hans D. Betz Kersten Schmidt Pierre Laroche Patrice Blanchet Wolf P. Oettinger Eric Defer Z. Dziewit J. Konarski 《Atmospheric Research》2009,91(2-4):564-573
During the past years a VLF/LF lightning detection network (LINET) was developed at the University of Munich, which provides continuous data for both research and operational purposes. In particular, the network introduces five new features: a) total lightning capability: both cloud-to-ground strokes (CG) and cloud lightning (IC) are measured; b) low-amplitude reporting: weak lightning events from discharge channel with currents well below 5 kA are detected within the central part of the network, whereby IC events dominate; c) new 3D-discrimination: a time-of-arrival method is utilized to separate CG from IC with good reliability, provided that the sensor baseline does not exceed ~ 250 km; d) IC emission height: for each cloud event a height is determined which is thought to reflect the central region of the involved channel; and e) optimised location accuracy: due to precision and combined action of all influential network components, complemented by site-error corrections, the position accuracy of strokes reaches an average value as small as ~ 150 m, whereby false locations (‘outliers’) rarely occur. During international co-operations LINET has been deployed in four continents: Europe (initially Germany), South America (area of Bauru, Brazil), Australia (around Darwin), and Central Africa (Benin). Since the features quoted above could be verified in the tests, a 65-sensor network was established in Europe and started on May 1, 2006, in co-operation with the service company nowcast. LINET covers a wide area approximately from longitude − 10° to 25° to latitude 35° to 66°; it is available for scientific projects and officially utilized by the German Weather Service for operational purposes. Meanwhile, the network was extended by deployment of additional sites so that it comprises about 90 sensors in 17 countries. 相似文献
366.
Manfred Birke Uwe Rauch Bodo Harazim Hans Lorenz Wolfgang Glatte 《Journal of Geochemical Exploration》2010
The market for mineral water has been growing steadily over the last few years. Germany is the country with the highest number of bottled mineral water brands (908 bottled water samples from 502 wells/brands were analyzed). The per capita consumption of mineral water in Germany in 2003 was 129 L. A wide range of values of one to seven orders of magnitude was determined for 71 elements in the bottled water samples analyzed by ICP-QMS, ICP-AES, IC, titration, photometric, conductometric and potentiometric methods. A comparison of the element concentrations and the legal limits for both bottled and tap water (EU, Germany, US EPA, WHO) shows that only 70% of the 908 mineral water samples fulfill the German and EU drinking water (i.e., tap water) regulations for all parameters (not including pH) for which action levels are defined. Nearly 5% of the bottled water samples not fulfill the German and EU regulations for mineral and table water. Comparison of our results with the current German and European action levels for mineral and table water shows that only 42 of the bottled water samples exceed the limits for one or more of the following elements: arsenic, nitrate, nitrite, manganese, nickel and barium concentrations. Ten of the bottled water samples contain uranium concentrations above the 10 μg/L recommended limit. 相似文献
367.
Bj?rn Sandstr?m Hans Annersten Eva-Lena Tullborg 《International Journal of Earth Sciences》2010,99(1):1-25
Red-staining of rocks due to fluid–rock interaction during hydrothermal circulation in fractures is a common feature in crystalline
sequences. In this study, red-stained metagranitic rock adjacent to fractures in Forsmark, central Sweden, has been studied
with emphasis on the mineral reactions and associated element mobility occurring during the alteration. The main mineral reactions
associated with the hydrothermal alteration are an almost complete saussuritization of plagioclase accompanied by total chloritization
of biotite. Magnetite has been partly replaced by hematite whereas quartz and K-feldspar were relatively unaffected by the
hydrothermal alteration. We show that redistribution of elements on the whole rock scale was very limited and is mainly manifested
by enrichment of Na2O and volatiles and depletion of CaO, FeO and SiO2 in the red-stained rock. However, on the microscale, element redistribution was more extensive, with both intragranular and
intergranular migration of e.g. Ca, K, Na, Al, Si, Fe, Ba, Cs, Rb, Sr, Ti and REEs. The altered rock shows a shift towards
higher total oxidation factors, but the change is smaller than 1σ and the red-staining of the rock is due to hematite dissemination
rather than a significant oxidation of the rock. An increase in the connected porosity is also observed in the altered rock. 相似文献
368.
Predicting riverine dissolved silica fluxes to coastal zones from a hyperactive region and analysis of their first-order controls 总被引:2,自引:1,他引:1
Jens Hartmann Nils Jansen Hans H. Dürr Akira Harashima Kenji Okubo Stephan Kempe 《International Journal of Earth Sciences》2010,99(1):207-230
Silicate weathering and resulting transport of dissolved matter influence the global carbon cycle in two ways. First by the
uptake of atmospheric/soil CO2 and second by providing the oceanic ecosystems via the fluvial systems with the nutrient dissolved silica (DSi). Previous
work suggests that regions dominated by volcanics are hyperactive or even “hot spots” concerning DSi-mobilization. Here, we
present a new approach for predicting DSi-fluxes to coastal zones, emphasizing “first-order” controlling factors (lithology,
runoff, relief, land cover and temperature). This approach is applied to the Japanese Archipelago, a region characterized
by a high percentage of volcanics (29.1% of surface area). The presented DSi-flux model is based on data of 516 catchments,
covering approximately 56.7% of the area of the Japanese Archipelago. The spatial distribution of lithology—one of the most
important first order controls—is taken from a new high resolution map of Japan. Results show that the Japanese Archipelago
is a hyperactive region with a DSi-yield 6.6 times higher than the world average of 3.3 t SiO2 km−2 a−1, but with large regional variations. Approximately 10% of its area exceeds 10 times the world average DSi-yield. Slope constitutes
another important controlling factor on DSi-fluxes besides lithology and runoff, and can exceed the influence of runoff on
DSi-yields. Even though the monitored area on the Japanese Archipelago stretches from about 31° to 46°N, temperature is not
identified as a significant first-order model variable. This may be due to the fact that slope, runoff and lithology are correlated
with temperature due to regional settings of the Archipelago, and temperature information is substituted to a certain extent
by these factors. Land cover data also do not improve the prediction model. This may partly be attributed to misinterpreted
land cover information from satellite images. Implications of results for Earth System and global carbon cycle modeling are
discussed. 相似文献
369.
370.
Tropical peatlands of SE-Asia represent a significant terrestrial carbon reservoir of an estimated 65 Gt C. In this paper we present a comprehensive data synthesis of radiocarbon dated peat profiles and 31 basal dates of ombrogenous peat domes from the lowlands of Peninsular Malaysia, Sumatra and Borneo and integrate our peatland data with records of past sea-level and climate change in the region. Based on their developmental features three peat dome regions were distinguished: inland Central Kalimantan (Borneo), Kutai basin (Borneo) and coastal areas across the entire region. With the onset of the Holocene the first peat domes developed in Central Kalimantan as a response to rapid post-glacial sea-level rise over the Sunda Shelf and intensification of the Asian monsoon. Peat accumulation rates in Central Kalimantan strongly declined after 8500 cal BP in close relation to the lowering rate of the sea-level rise and possibly influenced by the regional impact of the 8.2 ka event. Peat growth in Central Kalimantan apparently ceased during the Late Holocene in association with amplified El Niño activity as exemplified by several truncated peat profiles. Peat domes from the Kutai basin are all younger than ~8300 cal BP. Peat formation and rates of peat accumulation were driven by accretion rates of the Mahakam River and seemingly independent of climate. Most coastal peat domes, the largest expanse of SE-Asian peatlands, initiated between 7000 and 4000 cal BP as a consequence of a Holocene maximum in regional rainfall and the stabilisation and subsequent regression of the sea-level. These boundary conditions induced the highest rates of peat accumulation of coastal peat domes. The Late Holocene sea-level regression led to extensive new land availability that allowed for continued coastal peat dome formation until the present. The time weighted mean Holocene peat accumulation rate is 0.54 mm yr?1 for Central Kalimantan, 1.89 mm yr?1 for Kutai and 1.77 mm yr?1 for coastal domes of Sumatra and Borneo. The mean Holocene carbon sequestration rates amount to 31.3 g C m?2 yr?1 for Central Kalimantan and 77.0 g C m?2 yr?1 for coastal sites, which makes coastal peat domes of south-east Asia the spatially most efficient terrestrial ecosystem in terms of long term carbon sequestration. 相似文献