The Impact Of Extreme Summer Melt on Net Accumulation of an Avalanche Fed Glacier,as Determined by Ground‐Penetrating Radar

Glacier mass balance is more sensitive to warming than cooling, but feedbacks related to the exposure of previously buried firn and ice in very warm years is not generally considered in sensitivity studies. A ground‐penetrating radar survey in the accumulation area of Rolleston Glacier, New Zealand shows that five years of previous net accumulation was removed by melt from parts of the glacier above the long‐term equilibrium line altitude during a single negative mass balance year. Rolleston Glacier receives a large amount of accumulation from snow avalanches, which may temporarily buffer it from climate warming by providing additional mass that has accumulated at higher elevations, effectively increasing the elevation range of the glacier. However, glaciers reliant on avalanche input may have high sensitivity to climatic variations because the extra mass is concentrated on a small part of the glacier, and small variations in avalanche input could have a large impact on overall glacier accumulation. Further research is needed to better estimate the amount and spatial distribution of accumulation by avalanche in order to quantify the climate sensitivity of small avalanche‐fed glaciers.     

Local Extremes in the Lidar‐Derived Snow Cover of Alpine Glaciers

Snow deposition and redistribution are major drivers of snow cover dynamics in mountainous terrain and contribute to the mass balance of alpine glaciers. The quantitative understanding of inhomogeneous snow distribution in mountains has recently benefited from advances in measuring technologies, such as airborne laser scanning (ALS). This contribution further advances the quantitative understanding of snow distribution by analysing the areas of maximum surface elevation changes in a mountain catchment with large and small glaciers. Using multi‐annual ALS observations, we found extreme surface elevation changes on rather thin borders along the glacier margins. While snow depth distribution patterns in less extreme terrain have presented high inter‐annual persistence, there is little persistence of those extreme glacier accumulations between winters. We therefore interpret the lack of persistence as the result of a predominance of gravity‐driven redistribution, which has an inherently higher random component because it does not occur with all conditions in all winters. In highly crevassed zones, the lidar‐derived surface elevation changes are caused by a complex interaction of ice flux divergence, the propagation of crevasses and snow accumulation. In general, the relative contribution of gravitational mass transport to glacier snow cover volume was found to decrease for glaciers larger than 5 km² in the investigated region. We therefore suggest that extreme accumulations caused by gravitational snow transport play a significant role in the glacier mass balance of small to medium‐size glaciers and that they may be successfully parameterized by simple mass redistribution algorithms, which have been presented in the literature.     

A Small Glacier as an Index of Regional Mass Balance: Baby Glacier, Axel Heiberg Island, 1959–1992

Baby Glacier, Axel Heiberg Island, N.W.T., Canada is a small (0.6 km²), high-latitude (79°N), high-altitude (700–1200 m) glacier with a mass balance record extending from 1959–60 to the present. The record demonstrates shrinkage of the glacier, but a statistically significant trend is not evident. Correlations are strong between the mass balance of Baby Glacier and that of the nearby and much larger White Glacier, and also those of even larger, more distant glaciers. Thus programmes of measurement on small, simple ice bodies such as Baby Glacier can be representative of a large region. However, inter-annual changes are more accentuated for Baby Glacier. Baby Glacier does not meet all of the usual criteria for a representative glacier, but it straddles the regional equilibrium zone, a fact which helps to offset the disadvantages of its small size and limited altitudinal range. The equilibrium zone deserves to be an important focus for studies of high-arctic mass balance, with the aim of facilitating future measurement programmes which will rely on satellite remote sensing.     

A Mass Balance Model that Uses Low-altitude Meteorological Observations and the Area–Altitude Distribution of a Glacier

A glacier mass balance model that requires only low-altitude precipitation and temperature observations and the glacier's areaaltitude distribution is presented as an alternative to direct field measurements. Input to the model for South Cascade Glacier are daily weather observations at stations 30–60 km from the glacier and at altitudes 1300 to 1500 m lower than the glacier. The model relies on the internal consistency of mass balance variables that are generated by simulation using the low-altitude weather data. The daily values of such balance variables as snowline altitude, zero balance altitude, glacier balance, balance flux and the accumulation area ratio are correlated throughout the ablation season using two-degree polynomial regressions to obtain the lowest fitting error. When the minimum average error (or maximum R ²) is attained, the generated balances and other variables are considered to be real. A simplex optimization technique is used to determine the optimal coefficient values that are used in algorithms to convert meteorological observations to snow accumulation and snow and ice ablation. The independently produced simulation results for the 1959–1996 period are compared with balances measured at the glacier. The agreement between annual balances for individual years is fair and between long-term volume changes measured by the geodetic method is excellent.     

Vegetation development and carbon storage on a glacier foreland in the High Arctic, Ny-Ålesund, Svalbard

The distribution of organic carbon and its relationship to vegetation development were examined on a glacier foreland near Ny-Ålesund, Svalbard (79°N). In a 0.72-km² area, we established 43 study plots on three line transects along primary succession from recently deglaciated area to old well-vegetated area. At each plot, we measured the type and percent coverage of vegetation types. The organic carbon content of vegetation, organic soil, and mineral soil samples was determined based on their organic carbon concentration and bulk density. Cluster analysis based on vegetation coverage revealed five types of ground surfaces representing variations in the amounts and allocation patterns of organic carbon. In the later stages of succession, 7%–24% and 31%–40% of organic carbon was contained in the organic and deeper soil layers, respectively. Organic carbon storage in the later stages of succession ranged from 1.1 – 7.9 kg C m⁻². A larger amount of organic carbon, including ancient carbon in a raised beach deposit, was expected to be contained in much deeper soil layers. These results suggest that both vegetation development and geological history affect ecosystem carbon storage and that a non-negligible amount of organic carbon is distributed in this High Arctic glacier foreland.     

青海南部牧区前冬积雪变化及其预测的关系模型研究

利用1961-2008年青海南部牧区地面气象观测资料、74个环流特征量和北半球500 hPa高度场网格点资料,整理了地表积雪序列和雪灾年表,并对积雪的变化趋势和雪灾发生的机理进行了研究。结果表明,1961-2008年青南牧区共有16 a发生积雪灾害,占总年数的33.33%。在4 450 m以下,累计积雪量随海拔高度的升高而增加,在4 451 m以上,累计积雪量随海拔高度的升高而减小。典型多积雪年新地岛地区的冷空气偏强、高原低值系统活动偏多,新地岛的冷空气容易沿偏西北路径侵入青南高原与高空槽前的暖湿空气汇合,形成云雨的物理条件充分,降雪多、积雪厚。典型少积雪年环流形势与上述基本相反。10-12月北美区极涡面积偏大和欧亚经向环流偏强、10月欧亚经向环流偏强、11月大西洋欧洲环流型E型日数偏多、12月大西洋副高北界位置偏北均有利于前冬青藏高原高度场的偏低和青南牧区累计积雪量的偏多。这些环流因子在相反的配置下,容易导致青南牧区累计积雪量的偏少。前冬模拟预报方程对典型多积雪年和1993年以来的积雪变化趋势全部预测成功。     

Light-absorbing impurities on Keqikaer Glacier in western Tien Shan: concentrations and potential impact on albedo reduction

Light-absorbing impurities on glaciers are important factors that influence glacial surface albedo and accelerate glacier melt. In this study, the quantity of light-absorbing impurities on Keqikaer Glacier in western Tien Shan, Central Asia, was measured. We found that the average concentrations of black carbon was 2,180 ng/g, with a range from 250 ng/g to more than 10,000 ng/g. The average concentrations of organic carbon and mineral dust were 1,738 ng/g and 194 μg/g, respectively. Based on simulations performed with the Snow Ice Aerosol Radiative model simulations, black carbon and dust are responsible for approximately 64% and 9%, respectively, of the albedo reduction, and are associated with instantaneous radiative forcing of 323.18 W/m2(ranging from 142.16 to 619.25 W/m2) and 24.05 W/m2(ranging from 0.15 to69.77 W/m2), respectively. For different scenarios, the albedo and radiative forcing effect of black carbon is considerably greater than that of dust. The estimated radiative forcing at Keqikaer Glacier is higher than most similar values estimated by previous studies on the Tibetan Plateau, perhaps as a result of black carbon enrichment by melt scavenging. Light-absorbing impurities deposited on Keqikaer Glacier appear to mainly originate from central Asia, Siberia, western China(including the Taklimakan Desert) and parts of South Asia in summer, and from the Middle East and Central Asia in winter.A footprint analysis indicates that a large fraction(60%) of the black carbon contributions on Keqikaer Glacier comes from anthropogenic sources. These results provide a scientific basis for regional mitigation efforts to reduce black carbon.     

冰雪旅游可持续发展：理论与实证研究（英文）

北京冬奥会为中国冰雪旅游发展带来历史性奇迹。把握时代红利,助力中国冰雪旅游发展是机遇,也是挑战。本专辑通过优选18篇学术论文,从冰雪旅游开发与管理、冰雪旅游体验及其影响因素、冰雪旅游影响评估三个方面深入探讨了冰雪旅游现状与未来;同时也设立了“旅游文化与生态旅游”专栏,分享旅游前沿研究热点。本专辑研究层次丰富,内涵深厚。研究区域从全国到区域,再到市县,同时包括纵向研究和横向研究。研究方法具有实用性、前沿性、创新性,包含产业关联分析方法、核密度、空间自相关等地理空间分析方法、内容分析法、情感分析法、结构方程模型、德尔菲法、空间统计方法、地理探测器方法等多种方法。本期专辑将定性研究与定量研究相结合,提供了感知价值理论、制度演化理论等多种理论视角,构建了冰雪旅游遗产赛前评估模型、雪场综合休闲环境调节作用下的消费技术–出游半径决策的影响模型、冰川旅游资源开发适宜性评价模型、冰雪旅游情境下游客体验价值与忠诚度关系的模型等多种模型。以期能够为后冬奥时代冰雪旅游发展提供理论和实践指导,助力冰雪旅游朝着可持续和高质量方向发展。     

Younger Dryas Glaciation in Söderåsen, South Sweden: An Analysis of Meteorologic and Topographic Controls

In Söderåsen, South Sweden, various geomorphological investigations indicate that small, local glaciers were initiated at very low altitudes within the Skäralid rock canyon during the Younger Dryas period. Wind polish on boulders indicates that this period was characterised by easterly winds and drifting snow. Some new field observations are presented and the Söderåsen Younger Dryas reglaciation hypothesis is tested by means of empirical knowledge on glacier equilibrium line climate and an analytic geographical information system (GIS) experiment. The GIS analysis demonstrates that the deeply incised rock canyon represents a pronounced radiation shelter, while the empirical analysis emphasises the importance of strong snow drift from the east during the winter. Together, the two analyses indicate that the inferred Söderåsen Younger Dryas reglaciation is possible from a palaeoclimatic point of view, although conditions for glaciation may have been marginal to those of rock glacier initiation.     

Melt–water Accumulation on the Surface of the Greenland Ice Sheet: Effect on Albedo and Mass Balance

Satellite–derived albedo maps of the western part of the Greenland ice sheet (between 64.5 and 70.5 ^∘ N) reveal a north–south extending zone with relatively low albedos at some distance from the ice margin. In the literature it has been hypothesized that this "dark zone" is due to a local maximum in melt–water accumulation on the ice–covered surface. A plausible explanation for this maximum in melt–water accumulation is thatrelative to the situation within the "dark zone", melt–water accumulation is reduced at higher elevations by a smaller melt–water production rate whereas runoff occurs more easily at lower elevations where slopes are generally steeper. For the present paper AVHRR images from eight years (1990–1997) were analysed. The following indications confirming the "melt–water accumulation hypothesis" were found: (1) there is a significant correlation between the annual mean albedo lowering within the "dark zone" and the annual amount of melt as inferred from local mass–balance measurements; and (2) within each summer season the albedo lowering within the "dark zone" seems to respond to the melt–water production rate as inferred from local temperature measurements. The effect of melt–water accumulation on the albedo implies a positive feedback between the albedo and the amount of melt. It is estimated that approximately 40% of the interannual mass–balance variations in the "dark zone" are due to this feedback.     

The experimental governing of mobility and trade on the China‐Laos frontier: The Tai Lue case

This paper discusses the governing of subjects and objects' mobility in the context of trans‐border rice and corn trade on the China‐Laos frontier. It traces the attempts by a group of ethnic Tai Lue traders from China to assert themselves as ‘flexible subjects’ and economically triumphant actors on the Upper Mekong market in the era of economic regionalization. It illustrates how, between 2005 and mid‐2006, the traders' economic success relied on a variety of ‘border strategies’. ‘Border strategies’ include a gender‐balanced organization of trade, the instrumental deployment of trans‐border ethnicity, the appropriation of a Han style of business, the opportunistic reliance on the Chinese administration's ‘regime of graduated mobility’, and the enactment of a ‘war‐machine’ against Lao state agents. Yet, in late 2006, a new wave of state authoritarianism, enmeshed in corporate accumulation processes, inhibited the traders' success. The paper suggests that, unlike what some defenders of globalization and transnational theories maintain, in the age of economic regionalization, the alleged flexibility and increased mobility of subjects and objects across the borders of the Greater Mekong Subregion remain conditional on an unpredictable mechanism of loosening and tightening. This is part of a long‐applied governing pattern of ‘experimentation under hierarchy’ on the Sino‐Lao frontier.     

Local- and watershed-scale controls on the spatial variability of natural levee deposits in a large fine-grained floodplain: Lower Pánuco Basin, Mexico

This study examines spatial variations in natural levee deposits within the lower reaches of a large coastal plain drainage system. The Pánuco basin (98,227 km²) drains east-central Mexico, and is an excellent setting to examine the influence of watershed and local controls on the morphology and sedimentology of natural levees. Although many fluvial systems in the U.S. Gulf Coastal Plain have been investigated, the rivers in the Mexican Gulf Coastal Plain have received comparatively little attention. Lateral and downstream characteristics of natural levee morphology and sediment texture are considered within the context of meandering river floodplain deposits. Data sources include total-stations surveying, sediment samples of surficial levee deposits, topographic maps (1:50,000), and aerial photographs (1:40,000). The slope of natural levees average 0.0049 m/m, whereas the texture (D₈₄) of levee deposits averages 0.12 mm. Natural levee characteristics vary due to local- and watershed-scale controls. The lateral reduction in levee height displays a curvilinear pattern that coincides with an abrupt change in sediment texture. The downstream pattern of natural levee texture exhibits the influence of local-scale perturbations superimposed upon a larger watershed-scale trend. Disruption to the fining trend, either by tributary inputs of sediment or reworking of Tertiary valley deposits, is retained for a limited distance. The influence of the channel planform geometry on levee morphology is examined by consideration of the radius of curvature (R_c) of meander bends, and is inversely related to natural levee width. This suggests that the planform geometry of river channels exerts a control on the dispersal of flood sediments, and is responsible for considerable local variability in the floodplain topography. The average width of natural levees increases with drainage area, from an average of 747 m in the Moctezuma to an average of 894 m in the Pánuco. However, in the lower reaches of the Pánuco valley the width of natural levees rapidly decreases, which is associated with fining of the suspended sediment load. Thus, the reduction in natural levee width signifies an abrupt change in the directionality of cause–effect relationships at the watershed-scale. Findings from this study elucidate linkages between meandering river channels and floodplains for a large lowland alluvial valley.