Meteorological and runoff time-series characteristics in a small,high-Arctic glaciated basin,Svalbard     

A. J. Hodson  A. M. Gurnell  R. Washington  M. Tranter  M. J. Clark  J. O. Hagen 《水文研究》1998,12(3):509-526

This paper examines characteristics of meteorological and runoff time-series collected from the Brøggerbreen glacier basin, Svalbard, during 1991 and 1992. Proglacial discharge and electrical conductivity were monitored at two gauging stations: one immediately downstream of the terminus of Austre Brøggerbreen and another c. 2·5 km downstream, in order to assess the contribution of the intervening proglacial sandur. Meteorological time-series (incident radiation, wind speed and direction, air temperature and precipitation) were monitored on the proglacial sandur. Changes in wind direction, incident radiation receipt and air temperature were used as a basis for separating the time-series into different periods. These periods allowed the relative significance of advective and incident (short-wave) radiative forcing of air temperatures to be determined at diurnal and synoptic time-scales. The analysis shows that incident radiation dominated over advection in the forcing of diurnal variations in air temperature during all the periods. At the synoptic scale, both processes were periodically dominant in forcing air temperature variability. An examination of synoptic charts supports the use of ground level measurements to describe the effect of energy advection upon the synoptic air temperature variability and indicates the role of large-scale circulation patterns in the delivery of energy for ablation under different conditions. Interrelationships between the hydrological and meteorological time-series are then used to characterize the response of the glacierized part of the catchment to meteorological forcing throughout the two ablation seasons. The analyses show that the recession of the snowpack across the proglacial and glacial portions of the basin has an important effect on the catchment contributing area contributing to runoff and the lag between energy inputs and meltwater discharge outputs. © 1998 John Wiley & Sons, Ltd.  相似文献   

Glacial to Holocene terrigenous organic matter input to sediments from Orca Basin, Gulf of Mexico — A combined optical and biomarker approach     

A.N. Meckler  C.J. Schubert  P.A. Hochuli  B. Plessen  D. Birgel  B.P. Flower  K.-U. Hinrichs  G.H. Haug   《Earth and Planetary Science Letters》2008,272(1-2):251-263

In this study we assessed changes in the contribution of terrigenous organic matter (OM) to the Gulf of Mexico over the course of the last deglaciation (the last 25 kyr). To this end, we combined optical kerogen analyses with bulk sedimentary, biomarker, and compound-specific carbon isotope analyses. Samples were obtained from core MD02-2550 from Orca Basin (2249 m water depth at 26°56.77N, 91°20.74W) with temporal resolution ranging from multi-decadal to millennial-scale, depending on the proxy. All proxies confirmed larger terrigenous input during glacial times compared to the Holocene. In addition, the kerogen analyses suggest that much of the glacial OM is reworked (at least 50% of spores and pollen grains and 40% of dinoflagellate cysts). The Holocene sediments, in contrast, contain mainly marine OM, which is exceptionally well preserved. During the deglaciation, terrigenous input was generally high due to large meltwater fluxes, whereby discrepancies between different proxies call for additional influences, such as the change in distance to the river mouth, local productivity changes, and hydrodynamic particle sorting. It is possible that kerogen particles and the terrigenous biomarkers studied here represent distinct pools of land-derived OM with inputs varying independently.  相似文献   

Excavation of subglacial bedrock channels by seasonal meltwater flow          下载免费PDF全文

Flavien Beaud  Jeremy G. Venditti  Gwenn E. Flowers  Michele Koppes 《地球表面变化过程与地形》2018,43(9):1960-1972

Subglacial water flow drives the excavation of a variety of bedrock channels including tunnel valleys and inner gorges. Subglacial floods of various magnitudes – events occurring once per year or less frequently with discharges larger than a few hundred cubic metres per second – are often invoked to explain the erosive power of subglacial water flow. In this study we examine whether subglacial floods are necessary to carve bedrock channels, or if more frequent melt season events (e.g. daily production of meltwater) can explain the formation of substantial bedrock channels over a glacial cycle. We use a one‐dimensional numerical model of bedrock erosion by subglacial meltwater, where water flows through interacting distributed and channelized drainage systems. The shear stresses produced drive bedrock erosion by bed‐ and suspended‐load abrasion. We show that seasonal meltwater discharge can incise an incipient bedrock channel a few tens of centimetres deep and several metres wide, assuming abrasion is the only mechanism of erosion, a particle size of D=256 mm and a prescribed sediment supply per unit width. Using the same sediment characteristics, flood flows yield wider but significantly shallower bedrock channels than seasonal meltwater flows. Furthermore, the smaller the shear stresses produced by a flood, the deeper the bedrock channel. Shear stresses produced by seasonal meltwater are sufficient to readily transport boulders as bedload. Larger flows produce greater shear stresses and the sediment is carried in suspension, which produces fewer contacts with the bed and less erosion. We demonstrate that seasonal meltwater discharge can excavate bedrock volumes commensurate with channels several tens of metres to a few hundred metres wide and several tens of metres deep over several thousand years. Such simulated channels are commensurate with published observations of tunnel valleys and inner gorges. Copyright © 2018 John Wiley & Sons, Ltd.  相似文献   

Stability of supraglacial debris          下载免费PDF全文

Peter L. Moore 《地球表面变化过程与地形》2018,43(1):285-297

Rock debris on the surface of ablating glaciers is not static, and is often transported across the ice surface as relief evolves during melt. This supraglacial debris transport has a strong influence on the spatial distribution of melt, and is implicated in the formation of hummocky glacial topography in deglaciated terrain. Furthermore, as ice‐dammed lakes and ice‐cored slopes become increasingly common in deglaciating watersheds, there is rising concern about hazards to humans and infrastructure posed by mass‐wasting of ice‐cored debris. The existing quantitative framework for describing these debris transport processes is limited, making it difficult to account for transport in mass balance, hazard assessment, and landscape development models. This paper develops a theoretical framework for assessing slope stability and gravitational mass transport in a debris‐covered ice setting. Excess water pressure at the interface between ablating ice and lowering debris is computed by combining Darcy's law with a meltwater balance. A limit‐equilibrium slope stability analysis is then applied to hypothetical debris layers with end‐member moisture conditions derived from a downslope meltwater balance that includes production and seepage. The resulting model system constrains maximum stable slope angles and lengths that vary with debris texture, thickness, and the rate of meltwater production. Model predictions are compared with field observations and with digital elevation model (DEM)‐derived terrain metrics from two modern debris‐covered glaciers on Mount Rainier, USA. Copyright © 2017 John Wiley & Sons, Ltd.  相似文献   

Meltwater erosion process of frozen soil as affected by thawed depth under concentrated flow in high altitude and cold regions   总被引：1，自引：0，他引：1       下载免费PDF全文

Yunyun Ban  Tingwu Lei  Chao Chen  Zhe Yin  Dengfeng Qian 《地球表面变化过程与地形》2017,42(13):2139-2146

Changes in thawed depth of frozen soil caused by diurnal and seasonal temperature fluctuations are commonly found in high altitude and latitude regions of the world. These changes significantly influence hydrologic and erosion processes. Experimental data are necessary to improve the understanding and modeling of the phenomenon. Laboratory experiments were conducted in Beijing to assess the impacts of thawed soil depth, slope gradient, and flow rate on soil erosion by concentrated meltwater flow over an underlying frozen soil layer. Soil samples from watershed were filled in flumes, saturated before being frozen. After the soil was completely frozen, flumes were taken out of storage to thaw the frozen soil from top to the designed depths. Meltwater flow was simulated using a tank filled with water and icecubes at approximately 0°C. The erosion experiments involved four thawed soil depths of 1, 2, 5, and 10 cm; three slope gradients of 5°, 10°, and 15°; and three flow rates of 1, 2, and 4 l/min; and seven rill lengths of 0.5, 1, 2, 3, 4, 5, and 6 m. Sediment‐laden water samples were collected at the lower end of the flume for determination of sediment concentration. The results showed that sediment concentration increased exponentially with rill length to approach a maximum value. The sediment concentrations were closely correlated with thawed soil depth, flow rate, and slope gradient. Shallower thawed depths delivered more sediments than deeper thawed depths. Slope gradient was the primary factor responsible for severe erosion. The effect of flow rate on sediment concentration which decreased with increasing slope gradient, was not as significant as that of slope gradient. Results from these experiments are useful for understanding the effect of thawed soil depth on erosion process in thawed soils subject to freezing and for estimating erosion model parameters. Copyright © 2017 John Wiley & Sons, Ltd.  相似文献   

Differences and cause analysis of changes in lakes of different supply types in the north‐western Tibetan Plateau          下载免费PDF全文

Baojin Qiao  Liping Zhu 《水文研究》2017,31(15):2752-2763

Most lakes of the Tibetan Plateau were experiencing quick expansion in recent decades; a detailed study on the changes in lakes of different supply types will help to understand the cause of the changes by analysing area change of 34 lakes and water level change of eight lakes in the north‐western Tibetan Plateau. All lakes are classified into three types: non‐glacier‐fed lakes, upstream lakes and glacier‐fed lakes. The glacier‐fed lakes are separated into glacier‐fed_P1 (quick expansion region) and glacier‐fed_P2 (slow expansion region). Combining the changes in precipitation, temperature and evaporation, less precipitation may be the main reason for lake shrinkage from 1976 to 1996 and quickly increasing precipitation led to the lakes' expansion from 1996 to 2000. However, after 2000, upstream lakes remained in a stable state with slight variation, non‐glacier‐fed lakes and glacier‐fed_P2 lakes exhibited a slightly increasing rate with high precipitation and high evaporation, and glacier‐fed_P1 lakes still expanded quickly. On the basis of the assumption of same precipitation and evaporation, glacial meltwater may make an important contribution (>52%) to the increase in water storage of Bangdag Co and Meima Co. The results suggest that glacial meltwater augments the increased rate of glacier‐fed_P2 lakes and plays a much more important role in the expansion of glacier‐fed_P1 lakes compared to other lakes.  相似文献   

Role of sediment in solute acquisition in the Himalayan glacier meltwater stream,Gangotri glacier,Uttarakhand, India     

Mukesh K. Sharma  Renoj J. Thayyen  Shyamlal 《水文研究》2021,35(1):e14018

Low temperature in-stream solute acquisition in a glacial environment with very high suspended sediment is critical for downstream evolution of water chemistry. Present work is carried out on 18 km headwater reach from Gomukh (snout of the Gangotri glacier) to Gangotri along River Bhagirathi, India for understanding the hydrological processes controlling the solute acquisition in the glacial environment. This is the first attempt to conduct dissolution experiments with river bed sediments and meltwater considering different operating variables namely; contact time, seasonality, different sediment particle sizes, different sediment dose, effect of pH, wetting and crushing of bed sediments of the glacial stream. The role of sediment in low temperature solute acquisition process is characterized by sudden release of ions from the sediment in initial few seconds. Equilibrium time was observed to be 600 s (10 min). Further progressive increase in EC was observed from Gomukh to Gangotri, suggesting change in sediment surface characteristics/or source. Higher dissolution was observed from the bed sediments collected in June. It is found that the dissolution increases with increase in sediment doses but decreases with an increase in sediment particle size fraction. Higher solute acquisition was observed from crushed sediment because of an abundance of very fine particles having fresh, aggressive/reactive mineral surfaces which are capable of dissolution. The solute released from wetted sediment is significantly lower than the fresh sediment, which may be attributed to the destruction of microparticles adhering to mineral grains, the removal of fresh reactive surface sites, dissolution of rapidly weathered minerals such as calcite and evolution towards to equilibrium of the solution. Further, higher dissolution was observed with decrease in pH, which may be attributed to the availability of more hydrogen ion concentration of the solution, which favours more solute acquisition from sediment into meltwater.  相似文献   

Holocene temperature trends in the extratropical Northern Hemisphere based on inter‐model comparisons          下载免费PDF全文

Yurui Zhang  Hans Renssen  Heikki Seppä  Paul J. Valdes 《第四纪科学杂志》2018,33(4):464-476

  相似文献   

七一冰川消融末期融水化学日变化特征   总被引：5，自引：3，他引：2  

武小波  王宁练  李全莲 《冰川冻土》2009,31(6):1080-1085

2006年9月1-8日在祁连山七一冰川作用区水文总控点逐时采集河水样, 并分析水样的主要可溶离子含量、电导率以及pH, 研究冰川作用区水化学组成日变化特征. 结果表明: 消融末期河水中pH的平均值约为7.60, 与离子浓度时间变化过程一致, 说明是偏碱性物质的输入增加了融水中化学物质的含量;SO~(2-)_4, Ca~(2+)分别是浓度最大的阴、阳离子, 属于SO~(2-)_4+HCO~-_3-Ca~(2+)+Mg~(2+)型水. 河水中可溶性离子浓度日变化过程具有不对称性, 表现为快速降低和缓慢的增加过程, 与流量变化呈显著反相关, Pearson相关说明流量是冰川区水化学特征随时间变化的控制性因素;阳离子通量计算显示, 在七一冰川区达54.7 t·km~(-2)·a~(-1), 其日变化过程与流量正相关, 与离子浓度成反相关, 说明径流量也是控制离子通量的主要因素.  相似文献   

祁连山冰川水资源   总被引：24，自引：3，他引：24  

杨针娘 《冰川冻土》1988,(1)

利用本文提出的祁连山冰川融水径流模数的经验公式,估算出该区冰川融水径流为11.56×10~8m~3,占河西地区河川径流总量的12.5％。其时空分布不均匀,西部大于东部,夏季多于春季。  相似文献