Haidong Han

Glacier retreat as a result of climate warming and increased precipitation in the Tarim river basin, northwest China

Abstract The Tarim river basin, a river system formed by the convergence of nine tributaries, is the most heavily glacierized watershed in arid northwest China. In the basin, there are 11 665 glaciers with a total area of 19 878 km2 and a volume of 2313 km3. Glaciers in the basin play a significant role in the water resource system. It is estimated that they provide about 133 x 108 m3 of meltwater annually, contributing 39% of the total river runoff. Under the influence of global warming, northwest China has experienced a generally warmer and drier climate since the mid-19th century. However, a so-called ‘warm and wet transition’ has occurred since the late 1980s, evidenced by an increase in both precipitation and stream discharge in the Xinjiang Autonomous Region and neighboring regions. This paper describes how glaciers in the Tarim river basin have responded to such warming and increased precipitation, and the impact of these glacier changes. We analyzed the variations of more than 3000 glaciers since the 1960s using topographical maps, high-resolution satellite images and aerial photographs of the river basin. Our results indicate that glaciers in the basin have been mostly in retreat in the past 40 years, and ice wastage has significantly influenced water resources in the Tarim river basin. Estimation by a degree-day meltwater model shows the positive anomaly in stream runoff of the Tailan river can be partly attributed to the increase in glacier runoff (amounting to one-third of the stream discharge), and a rough estimation using observed average ablation on the termini of 15 glaciers in China verifies that the mass loss calculated by a glacier area-volume relation is reasonable.

Backwasting rate on debris-covered Koxkar glacier, Tuomuer mountain, China

A physically based energy-balance model with improved parameterization of solar radiation for a sloped ice surface has been developed to estimate the backwasting rate of an ice cliff in a debris-covered area. The model has been tested against observations between 5 August and 5 September 2008 on 38 ice cliffs in the debris-covered area of Koxkar glacier, Tuomuer mountain, China. We calculated that the energy-balance model gave a good estimate of the backwasting rates, with errors in the range � 1.96 cm d -1 and root-mean-square errors of 0.99 cm d -1 . Errors arising from setting of surface albedo and turbulent flux parameterization were limited. We found that shortwave radiation is the most important heat source for ice-cliff ablation, contributing about 76% of the total heat available for ice melt, while the sensible heat flux provides nearly 24% of the total heat for ice-cliff wastage. The latent heat flux and net longwave radiation are comparatively small according to the model calculation. The mean backwasting rate of ice cliffs in the debris-covered area of Koxkar glacier is estimated at 7.64 m a -1 when the winter ablation is neglected. With this annual backwasting rate and given a mean slope angle of 46.48, the backwasting of ice cliffs produces about 1.60 � 10 6 m 3 of meltwater, accounting for about 7.3% of the total melt runoff from the debris-covered area.

Glacier changes during the past century in the Gangrigabu mountains, southeast Qinghai-Xizang (Tibetan) Plateau, China

Abstract The present research focuses on glacier changes in the southeast of the Qinghai–Xizang (Tibetan) Plateau, where most of the temperate glaciers in China are located. Our results show that the 102 measured glaciers in the region have all retreated between 1915 and 1980, with total area and volume decreases of 47.9 km2 and 6.95 km3, respectively. The extrapolated mass loss of all glaciers in the Gangrigabu mountains amounted to 27 km3, 9.8% of the ice mass in 1915. Between 1980 and 2001, glaciers in the region have also experienced a general retreat; however, up to 40% of the glaciers were advancing. Our analysis demonstrates that precipitation in the studied area has increased substantially since the mid-1980s. This precipitation increase is likely to bring about a positive mass balance for glaciers in the region, so that the retreat of retreating glaciers might slow down or even turn into advance. Considering the sensitivity of the temperate glaciers in the region and the uncertainty in climate projections, more attention must be paid to glacier changes in the southeast Tibetan Plateau region.

Modeling Hydrologic Response to Climate Change and Shrinking Glaciers in the Highly Glacierized Kunma Like River Catchment, Central Tian Shan

AbstractArid and semiarid lowland areas of central Asia are largely dependent on fluvial water originating from the Tian Shan. Mountain glaciers contribute significantly to runoff, particularly in summer. With global warming, the total glacier area in the Kunma Like River catchment declined by 13.2% during 1990–2007. For future water resources, it is essential to quantify the responses of hydrologic processes to both climate change and shrinking glaciers in glacierized catchments, such as the headwaters of the Tarim River. Thus, a degree-day glacier melt algorithm was integrated into the macroscale hydrologic Variable Infiltration Capacity model (VIC). Good results were obtained for monthly runoff simulations in the Kunma Like River catchment, which suggest that the extended VIC has acceptable performance. Because of increased precipitation and air temperature, annual runoff in the catchment has increased by about 4.07 × 108 m3 decade−1 during 1984/85–2006/07. Under the assumption of the same climatic con...

The relationship between runoff and ground temperature in glacierized catchments in China

A single parameter index method, in which ground temperature and air temperature is the sole input variable, respectively, is used to evaluate and compare the glacial runoff in three typical glacier catchments, Dongkemadi glacier catchment in Tibetan plateau, Koxkar glacier catchment and the headwater catchment of Urumqi River catchment in Tianshan Mountains in West China. The method based on ground temperature is an attempt to evaluate glacier runoff in elevated terrains, as few studies have focused specifically on the association between glacier runoff and ground temperature. The results identify ground temperature versus a certain depth, which is a critical factor that affected glacier hydrological processes and showed that runoff data is much better correlated with ground temperature than air temperature. Especially, at the latter two catchments, the largest coefficients of exponential relationship R2 between glacier runoff and ground temperature are 0.9 and 0.83, respectively. The accuracy of the method makes it possible to estimate the glacier runoff with a certain depth ground temperature at a certain site, which may provide a new approach to evaluate the glacier runoff for areas where there is a lack of observation data.

Validation of the Accuracy of Different Precipitation Datasets over Tianshan Mountainous Area

Precipitation is one of the important water supplies in the arid and semiarid regions of northwestern China, playing a vital role in maintaining the fragile ecosystem. In remote mountainous area, it is difficult to obtain an accurate and reliable spatialization of the precipitation amount at the regional scale due to the inaccessibility, the sparsity of observation stations, and the complexity of relationships between precipitation and topography. Furthermore, accurate precipitation is important driven data for hydrological models to assess the water balance and water resource for hydrologists. Therefore, the use of satellite remote sensing becomes an important means over mountainous area. Precipitation datasets based on station data or pure satellite data have been increasingly available in spite of several weaknesses. This paper evaluates the usefulness of three precipitation datasets including TRMM 3B43_V6, 3B43_V7, and Asian Precipitation Highly Resolved Observational Data Integration Towards Evaluation with rain gauge data over Tianshan mountainous area where precipitation data is scarce. The results suggest that precipitation measurements only provided accurate information on a small scale, while the satellite remote sensing of precipitation had obvious advantages in basin scale or large scale especially over remote mountainous area.

The Temporal Precipitation in the Rainy Season of Koxkar Glacier Based on Observation Over Tianshan Mountain in Northwest of China

Precipitation, as one of important input variable for land surface hydrologic and ecological models, shows a high spatial and temporal variation. The daily precipitation by manual measurement is collected in Koxkar glacier catchment in rainy season during the period of 2009–2016, and hourly precipitation by standard tipping rain gauge is collected from May 19 to August 22 in 2016. Comparing the manual and standard tipping rain gauge, the performance of standard tipping rain gauge is suited in Koxkar glacier catchment in rainy season. The distribution of hourly precipitation is analyzed. The results have shown that precipitation is occurred more in daytime than in night, and frequency is concentrated at 15:00 to 17:00. The trend of precipitation and precipitation days are consistent at night, but obvious inconsistency in the daytime. These characteristics of precipitation have important role for further understanding of glacier changes with climate change.

Regimes of runoff components on the debris-covered Koxkar glacier in western China

By using a degree-day based distributed hydrological model, regimes of glacial runoff from the Koxkar glacier during 2007–2011 are simulated, and variations and characteristics of major hydrological components are discussed. The results show that the meltwater runoff contributes 67.4%, of the proglacial discharge, out of which snowmelt, clean ice melting, buried-ice ablation and ice-cliff backwasting account for 22.4%, 21.9%, 17.9% and 5.3% of the total melt runoff, respectively. Rainfall runoff is significant in mid-latitude glacierized mountain areas like Tianshan and Karakorum. In the Koxkar glacier catchment, about 11.5% of stream water is initiated from liquid precipitation. Spatial distributions for each glacial runoff component reveal the importance of climatic gradients, local topography and morphology on glacial runoff generation, and temporal variations of these components is closely related to the annual cycle of catchment meteorology and glacier storage. Four stages are recognized in the seasonal variations of glacier storage, reflecting changes in meltwater yields, meteorological conditions and drainage systems in the annual hydrological cycle.

Carbon dioxide flux in the ablation area of Koxkar glacier, western Tien Shan, China

Abstract Accelerating loss of glacial mass caused by rising global temperatures has significant implications. The global cycle of the greenhouse gas CO2 is also associated with mineral weathering and glaciation. In glaciated areas, most estimates of atmospheric CO2 consumption are confined to chemical ionic mass balance or analog modeling methods. We applied the gradient method to the surface of Koxkar glacier, western Tien Shan, China, for a 5 month period during 2012. The overall net glacier-system CO2 exchange (NGE) rate was measured as -0.05 and -0.07mmol m–2 s–1 for regions of exposed ice and supraglacial moraine, respectively. This suggests that atmospheric CO2 drawdown may occur during ice melting because of consumption of H+ by CO2 hydrolysis that occurs in solutions. Using the degree-day model to calculate glacier ablation in bare-ice regions and considering characteristics of the NGE rate in the supraglacial debris region with the support of GIS, the daily NGE rate was estimated to be -1.23 ± 0.17μmmol m–2 d–1 between Julian days 125 and 268 of 2012. These findings present a new approach for modeling the dynamics of glacial CO2 sinks undergoing melting, and develop an understanding of the mechanism of atmospheric CO2 exchange.