[1] This study analyzes long-term climate and glacier records to examine climate change and glacier response over the past 45 years in Urumqi River source region, the Tianshan Mountains of China. The results show that summer temperature and annual precipitation near the glacier increased by 0.8°C and 87 mm (19%), respectively, during the study period. The glacier continuously retreated from 1962 to 2003, with the cumulated mass balance being À10,032 mm, or 20% of the glacier volume. Annual basin runoff has significantly increased by 413 mm or 62% during 1980 -2003 due to precipitation increase and enhanced glacier melt caused by summer climate warming. Both summer precipitation and temperate are negatively correlated with mass balance and positively associated with runoff. Relative to precipitationmass balance relation, the regression between temperature and mass balance is much stronger, indicating that summer temperature controls glacier mass balance and runoff changes. Citation: Ye, B

Abstract:On the basis of the field measurements of changes in groundwater level and plant species abundance along nine transects crossing the Tarim River in Xinjiang, China, we examined the responses of groundwater and plant communities to a government-controlled 7-year recharge regime to the lower reaches of the river. Our results showed that the water recharges considerably lifted the groundwater table on both sides of the river course. The 6-8-m groundwater depths before the water recharges rose to 2-4 m after the recharges. In the transverse direction, the response of the groundwater table could be observed at as far as 850 m from the river course, and the affected Populus euphratica could be observed at 700 m. However, we did not observe significant influence of the water recharges on herbaceous plants. We infer that the plant communities will be benefited more from the combination of overbank flows and stream aquifer recharge than from sole stream aquifer recharge. Such a combination may maximize the ecological benefits of water conveyance and accelerate the restoration of the damaged arid ecosystems in this area.

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[1] Direct measurement of the thickness of mountain glaciers is difficult over large areas, yet knowledge of the thickness is essential for calculating their volumes and future evolution. We develop a new method for estimating the ice thickness along glacier flow lines, using the "perfect-plasticity" rheological assumption that relates the thickness and surface slope to a yield stress. Previous studies have used this assumption with the shallow-ice approximation to estimate the ice thickness, but the standard approach neglects the effect of side drag on glacier stress balance. Our method addresses this shortcoming and extends the standard method by accounting for the side drag via the glacier width. Besides the assumed yield stress, the inputs for our method are the outline and surface topography of the glacier; surface velocity and mass balance data are unnecessary. We validated the extended method on five glaciers in northwest China where thickness data are available from radio echo soundings, finding that it can reproduce measured thicknesses with a mean absolute error of 11.8% (like the standard method). Moreover, for long glacier tongues confined to flow between parallel valley sides, this method is found to give more accurate thickness estimates than does the standard method, with a mean absolute error of as low as 5.3%. Sensitivity analysis shows that the estimated ice thickness depends strongly on yield stress and surface slope and less strongly on glacier width. Because this method is physically more realistic than the standard method and its inputs are easily derivable from remote-sensing observations, it has the potential to be used for processing large glacier data sets.

Cryoconite granules are dark-colored spherical aggregates of organic and inorganic material on glacier ice, and are commonly observed on glaciers the world over. The structure of cryoconite granules on Ürümqi glacier No. 1, Tien Shan, China, was analyzed. Granules were distributed over the entire ice surface of the ablation area, and ranged in size from 0.26 to 3.5 mm (mean 1.1 mm). The granule surface was densely covered with filamentous cyanobacteria. Microscopy of a thin section revealed various inner structures. Most granules had concentric layers of dense organic matter, which are probably derived from annual growth of the granules by the activity of cyanobacteria. The number of layers averaged 3.5 and ranged up to 7, which is likely to indicate their mean and maximum growth ages, respectively. Some granules contained two or more subgranules, showing that small granules had combined and enlarged. Such structures suggest that granule formation was mainly due to the activity of filamentous cyanobacteria, and that the granules repeatedly grew and disintegrated over a cycle of several years on the glacier.