The tunnel through Torghatten,northern Norway: Landforms and discussion of formation     

《Norsk geografisk tidsskrift. Norwegian journal of geography》2012,66(4):268-271

The tunnel through the mountain of Torghatten, in northern Norway, is generally regarded as a product of wave action. The tunnel is above the late Weichselian marine limit. Fresh looking polished bedrock that resembles subglacial ice-sculptured and meltwater forms, p-forms, occurs near the opening to the landward eastern side of the tunnel and inside. Most likely, the tunnel is a polygenetic formation. Storm action during deglaciations and also subglacial meltwater drainage and plastically sliding ice during glaciations have been active processes in the formation of the tunnel.  相似文献   

夏季西北冰洋表层淡水分布的总碱度示踪研究   总被引：1，自引：0，他引：1       下载免费PDF全文

高众勇  孙恒  陈立奇  张凡 《极地研究》2012,24(2):120-128

利用中国第三次北极科学考察在西北冰洋所进行的海水总碱度的测量,通过海水、海冰融化水以及河源淡水三个端元总碱度特征的显著差异计算西北冰洋夏季表层海水中淡水所占的比例。研究表明,西北冰洋海冰融化水所占比例最大区域在加拿大海盆区75°N附近,这是冰缘带位置,往北向高纬度的冰密集中逐渐增加。而河源淡水的组份则与北冰洋的环流密切相关,并且在西北冰洋水体中逐渐累积。  相似文献   

The application of artificial neural networks to simulate meltwater runoff of Keqikaer Glacier,south slope of Mt. Tuomuer,western China     

Chen Caiping  Ding Yongjian 《Environmental Geology》2009,57(8):1839-1845

Because glacial melting provides a significant amount of surface water resources, especially in cold arid regions, it is critical that effective methods be developed for predicting their behavior. Glacier runoff differs from other types of stream flows, being characterized by large diurnal fluctuations, with maximum discharge during the summer months. Moreover, the size and remoteness of glaciers makes them difficult to study directly. Hence, developing effective modeling techniques is our best hope for understanding and predicting glacial melting phenomena. In the past, physics-based models have been used with some success. In this study, conducted in 2003 and 2004 on the Keqikaer Glacier on the south slope of Mt. Tuomuer, however, we used the newer artificial neural networks (ANNs) modeling technique. As the input nerve cell, we used the hourly wind speed, precipitation, air temperature, radiation balance, and ground temperature; the output nerve cell was the diurnal runoff at the glacial terminus. We then analyzed the simulated results under different scenarios by varying the input-nerve-cell parameters. It was found that ANN can simulate the process of glacier meltwater runoff successfully when basic parameters such as air temperature, precipitation and radiation balance are few. The results indicate that ANN can simulate the process of glacial meltwater runoff quite well, and that meteorological variables could in fact be used successfully to simulate glacier meltwater runoff using the ANN method.  相似文献   

The extension of the Late Weichselian/Late Devensian ice sheets in the North Sea Basin     

Jürgen Ehlers  Robin Wingfield 《第四纪科学杂志》1991,6(4):313-326

The distribution of large channel-like features, comprising Weichselian/Devensian incisions, in the western North Sea provides evidence for a much larger extension of the last ice sheet than currently assumed. Morphological comparison of the incisions with those in North Germany and Poland reveals a striking similarity in shape and distribution. The features on the North Sea floor are interpreted as being formed by meltwater erosion within the margin of the ice sheet. The widespread absence of Weichselian/Devensian till in the area under consideration may be attributed to later erosion. Large-scale reworking and redistribution of sediments is indicated by the complete sediment infill of the majority of the incisions.  相似文献   

Temporal changes in subglacial meltwater activity: field evidence from the late Devensian in the north of Ireland     

Jasper Knight   《Sedimentary Geology》2003,160(4):291-307

Temporal changes in meltwater abundance, distribution and characteristics (controlling subglacial processes and ice sheet dynamics) can be inferred from subglacial sediment successions. Field evidence for changes in subglacial meltwater characteristics over time is presented from two sites (Doonan, Drummee) near a former late Weichselian (Devensian) ice centre in the north of Ireland. On a macroscale, both sites investigated show subglacial diamicton overlying glacially planated bedrock platforms. In more detail, primary sedimentary structures and facies variability show a complex relationship between depositional processes and meltwater characteristics at the ice/bed interface (IBI). Sedimentary evidence suggests sediment transport and deposition took place by low-viscosity subglacial slurries (mobile sediment–meltwater admixtures), which are part of a continuum between the processes of subglacial sediment deformation and subglacial meltwater flooding. Subtle changes in meltwater abundance and distribution at the IBI controlled slurry rheology, mechanisms of particle support and detailed sediment depositional processes.  相似文献   

Luminescence dating of shoreline sediments indicates a late deglacial lake-level rise of Selin Co on the central Tibetan Plateau     

《Quaternary Geochronology》2022

The palaeo-shorelines around the lakes on the Tibetan Plateau can be used to reconstruct water level variations, which serve as sensitive indicators of hydroclimate change. Extensive studies have been carried out to constrain the Holocene lake level fluctuations by dating shorelines with a variety of methods (e.g., luminescence, ¹⁴C, ¹⁰Be and U–Th series). In comparison, the timing of the lake level variations during the last glacial and subsequent deglaciation periods has been rarely studied. The driving factors of such changes, therefore, remain elusive. In this study, we performed a detailed luminescence dating investigation on six samples taken from a nearshore sedimentary outcrop in the south of Selin Co basin. The post-IR IRSL signals measured at 225 °C (pIRIR₂₂₅) on sand-sized K-feldspar grains demonstrated a generally good behavior and yielded reliable chronologies, while the optically stimulated luminescence (OSL) signals of quartz showed systematical age underestimation, which was attributed to anomalous fading. Six pIRIR₂₂₅ ages ranging from 15 to 10 ka suggested that the lake level of Selin Co during the last deglaciation reached up to 40–45 m high above the modern lake level. In view of the regional precipitation and temperature proxy records, we consider that the glacier meltwater supply has likely been the primary contributor to the lake highstands during the last deglaciation.  相似文献   

Contemporary rates of chemical denudation and atmospheric CO2 sequestration in glacier basins: an Arctic perspective     

Andy Hodson  Martyn Tranter  Geir Vatne 《地球表面变化过程与地形》2000,25(13):1447-1471

This paper presents new estimates of solute fluxes from five high Arctic glacier basins in Svalbard. These estimates are combined with data from two other glacier basins to assess the effectiveness of chemical denudation on Svalbard and to estimate rates of temporary (or transient) CO₂ drawdown. We use a solute provenance model to partition solutes into marine, aerosol, atmospheric and crustal components and to estimate their annual fluxes. Crustally derived solute fluxes are equivalent to a mean chemical denudation rate of 350 Σmeq⁺ m⁻² a⁻¹ for Svalbard (range: 160–560 Σmeq⁺ m⁻² a⁻¹), which lies within the global range of 94–4200 Σmeq⁺ m⁻² a⁻¹ for 21 glacier basins in the northern hemisphere, and is close to the continental average of 390 Σmeq⁺ m⁻² a⁻¹. Specific annual discharge is the most significant control upon chemical denudation in the glacierized basins, and basin lithology is an important secondary control, with carbonate‐rich and basaltic lithologies currently showing the greatest chemical denudation rates. Estimates of transient CO₂ drawdown are also directly associated with specific annual discharge and rock type. On Svalbard transient CO₂ drawdown lies in the range 110–3000 kg C km⁻² a⁻¹, whilst the range is 110–13000 kg C km⁻² a⁻¹ for the northern hemisphere glacial data set. Transient CO₂ drawdown is therefore usually low in the Svalbard basins unless carbonate or basalt rocks are abundant. The analysis shows that a large area of uncertainty in the transient CO₂ drawdown estimates exists due to the non‐stoichiometric release of solute during silicate hydrolysis. Silicate hydrolysis is particularly non‐stoichiometric in basins where the extent of glacierization is high, which is most probably an artefact of high flushing rates through ice‐marginal and subglacial environments where K‐feldspars are undergoing mechanical comminution. Copyright © 2000 John Wiley & Sons, Ltd.  相似文献   

Global meltwater discharge and the deglacial sea-level record from northwest Scotland     

Ian Shennan 《第四纪科学杂志》1999,14(7):715-719

Quantitative models of Earth–ice-sheet–ocean interactions predict that periods of rapid eustatic sea-level rise, indicating enhanced meltwater discharge to the oceans, should be manifest in the relative sea-level histories from sites within the limits of Late Devensian ice sheets. Analysis of a record of relative sea-level change for the last 16000 calendar years from Northwest Scotland constrains the magnitude and timing of two major pulses of meltwater, ca. 14000 and ca. 11300 cal. yr BP, inferred from coral records. The ca. 14000 cal. yr BP event saw a temporary doubling of the flux of meltwater, but existence of the second major event at ca. 11300 cal. yr BP is not supported by the data from northwest Scotland. Copyright © 1999 John Wiley & Sons, Ltd.  相似文献   

Routing of canopy drip in the snowpack below a spruce crown     

Michael Bründl  Martin Schneebeli  Hannes Flühler 《水文研究》1999,13(1):49-58

Snow that is retained by a forest canopy may either sublimate or evaporate directly from the crown or drop as snow clumps or meltwater to the ground. Redistributed snow and meltwater affect the snow structure and prevent the formation of mechanically weak layers, which is the prerequisite for avalanche formation in forests. In this paper we describe the results of dye tracer experiments conducted in a subalpine forest near Davos, Switzerland. Before a snowfall event we stained snow‐free branches of a spruce with a dye tracer solution. After snowfall the coloured meltwater dripping from the branches down on to the snowpack stained the percolation pathways of the meltwater in the snowpack. Photographs of the snow profiles indicate that the meltwater seeped almost vertically through the isothermal snowpack to the soil surface not exceeding the projected crown edge. Meltwater of different events moves along different preferential flow channels in the snow suggesting that old channels are not non‐conducting and additional meltwater fronts create new channels. Copyright © 1999 John Wiley & Sons, Ltd.  相似文献   

An approach to hydrograph classification     

David M. Hannah  Barnaby P. G. Smith  Angela M. Gurnell  Glenn R. McGregor 《水文研究》2000,14(2):317-338

The stream hydrograph is an integration of spatial and temporal variations in water input, storage and transfer processes within a catchment. For glacier basins in particular, inferences concerning catchment‐scale processes have been developed from the varying form and magnitude of the diurnal hydrograph in the proglacial river. To date, however, such classifications of proglacial diurnal hydrographs have developed in a relatively subjective manner. This paper develops an objective approach to the classification of diurnal discharge hydrograph ‘shape’ and ‘magnitude’ using a combination of principal components analysis and cluster analysis applied to proglacial discharge time‐series and to diurnal bulk flow indices. The procedure is applied to discharge time‐series from two different glacier basins and four separate ablation seasons representing a gradient of increasing hydrological perturbation as a result of (i) variable water inputs generated by rainstorm activity and (ii) variable location and response of hydrological stores through a systematic decrease in catchment glacierized area. The potential of the technique for application in non‐glacial hydrological contexts is discussed. Copyright © 2000 John Wiley & Sons, Ltd.  相似文献