The ground temperature and active layer are greatly influenced by vegetation in the Greater Hinggan Mountains in Northeastern China.However,vegetation,as a complex system,is difficult to separate the influence of its different components on the ground thermal regime.In this paper,four vegetation types,including a Larix dahurica-Ledum palustre var.dilatatum-Bryum forest（P1）,a L.dahurica-Betula fruticosa forest（P2）,a L.dahurica-Carex tato forest（P3） in the China Forest Ecological Research Network Station in Genhe,and a Carex tato swamp（P4） at the permafrost observation site in Yitulihe,have been selected to study and compare their seasonal and annual influence on the ground thermal regime.Results show that the vegetation insulates the ground resulting in a relatively high ground temperature variability in the Carex tato swamp where there are no tree stands and shrubs when compared with three forested vegetation types present in the area.Vegetation thickness,structure,and coverage are the most important factors that determine the insulating properties of the vegetation.In particular,the growth of ground cover,its water-holding capacity and ability to intercept snow exert a significant effect on the degree of insulation of the soil under the same vegetation.
Similar to most mountain glaciers in the world, Urumqi Glacier No. 1 （UG1）, the best observed glacier in China with continued glaciological and climatological monitoring records of longer than 50 years has experienced an accelerated recession during the past several decades. The purpose of this study is to investigate the acceleration of recession. By taking UG1 as an example, we analyze the generic mechanisms of acceleration of shrinkage of continental mountain glaciers. The results indicate that the acceleration of mass loss of UG1 commenced first in 1985 and second in 1996 and that the lat- ter was more vigorous. The air temperature rises during melting season, the ice temperature augment of the glacier and the albedo reduction on the glacier surface are considered responsible for the accelerated recession. In addition, the simulations of the accelerated shrinkage of UG1 are introduced in this article.
To evaluate the water storage and project the future evolution of glaciers, the ice-thickness of glaciers is an essential input. However, direct measurements of ice thickness are labo- rious, not feasible everywhere, and necessarily restricted to a small number of glaciers. In this article, we develop a simple method to estimate the ice-thickness along flow-line of mountain glaciers. Different from the traditional method based on shallow ice approximation （SIA）, which gives a relationship be- tween ice thickness, surface slope, and yield stress of glaciers, the improved method considers and pre- sents a simple way to calibrate the influence of valley wall on ice discharge. The required inputs are the glacier surface topography and outlines. This shows the potential of the method for estimating the ice-thickness distribution and volume of glaciers without using of direct thickness measurements.
To investigate the seasonal variability and potential environmental significance of trace elements in mountain glaciers, the surface snow and snow pit samples were collected at Urumqi Glacier No. 1 （43°06′N, 86°49′E, 4 130 m a.s.l.）, eastern Tianshan （天山）, from September 2002 to September 2003, and analyzed for Li, V, Cr, Mn, Co, Cu, and Ba. The samples were acidified （leached） in a manner intended to reasonably approximate the extent to which the natural hydrologic and weathering cycles would liberate elements from mineral grains （dusts） in the ice and snow into the environment. The mean concentrations of Li, V, Cr, Mn, Co, Cu, and Ba are 0.2, 1.1, 0.8, 14.8, 0.1, 0.7, and 3.2 ng/g in surface snow but 1.0, 2.2, 1.8, 92.4, 0.8, 2.9, and 16.2 ng/g in snow pits, respectively. Input varies seasonally： in general, concentrations in the winter are higher than those in the summer. The trace elements are somewhat enriched （relative to expected abundances in material taken di- rectly from the earth＇s crust） and similar to what is observed in both pre-industrial and modern atmospheric dusts, although some anthropogenic components from nearby industrial cities may be present. Concentration vertical profiles can be redistributed in the post-depositional process, which may cause loss of trace elements in the summer.
ABSTRACT： Samples were continuously collected from aerosol, fresh snow, and snow pits on Glacier No. 1 at Urumqi River source in eastern Tianshan （天山） Mountains. The deposition processes and the characteristics of mineral dust microparticles from aerosol to fresh snow, and then evolution to the snow pit were determined. Total dust microparticle concentration in the surface snow and aerosol showed a similar temporal variation trend, which was strongly associated with regional and local at- mospheric circulation in the Tianshan Mountains region of Central Asia. Especially from November to February, the correlation coefficient of microparticles concentration in surface snow and aerosol is very high （R2=0.7）. Vertical profiles of microparticles in the snow pits showed that observed dust layers were in high correlation with concentration peaks of large microparticles （d〉10 μm）, but low correlation with that of fine microparticles （d〈1μm）. Moreover, explicit post-depositional process of dust particles was studied by tracking some typical dust concentration peaks in the snow pit. We find that late sum- mer is a key period for post-deposition of dust particles in the snow, as particle concentration peaks in the snow pit evolve intensely during this period. Such evolutional pattern of large particles makes it possible to preserve information of atmospheric dust in the snow, which offers an available proof to reconstruct historical climate using ice cores on Glacier No. 1 and other gla- ciers in the Tianshan Mountains.
