Donghui Shangguan

The retreat of glaciers in response to recent climate warming in western China

Abstract Glaciers in China are primarily located in the Tibetan Plateau (TP) and surrounding high mountains. The Chinese Glacier Inventory indicates that there are 46 377 glaciers in western China. Meteorological records indicate that air temperature in western China has risen by 0.2˚C per decade since 1951, and 1998 was the warmest year; precipitation in the region increased by 5–10% per decade from 1953 to 1997. Using remote-sensing and Geographic Information System methods, we have monitored the changes in >5000 glaciers over the past 50 years. We conclude that >80% of glaciers in western China have retreated, losing 4.5% of their combined areal coverage, although some glaciers have advanced. In addition, regional differences characterize glacier changes over the past few decades. For example, glaciers in the central and northwestern TP were relatively stable, while glaciers in the mountains surrounding the TP experienced extensive wastage. Mass-balance variations for some glaciers show accelerated ice shrinkage in the last two decades.

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.

Glacier changes in the west Kunlun Shan from 1970 to 2001 derived from Landsat TM/ETM+ and Chinese glacier inventory data

Abstract Recent studies have indicated that widespread wastage of glaciers in western China has occurred since the late 1970s. By using digitized glacier outlines derived from the 1970 inventory and Landsat satellite data from 1990/91 to 2001, we obtained area changes of about 278 glaciers with a total area of 2711.57 km2 in the heavily glaciated west Kunlun Shan (WKS) in the northern Tibetan Plateau (TP). Results indicate that the prevailing characteristic of glacier variation is ice wastage, and glacier area decreased by 10 km2 (0.4% of the total 1970 area) between 1970 and 2001. Both the south and north slopes of the WKS presented shrinkage during 1970–2001, but whereas on the north slope a slight enlargement of ice extent during 1970–90 was followed by a reduction of 0.2% during 1990–2001, on the south slope the glacier area decreased by 1.2% during 1970–91, with a small increment of 0.6% during 1991–2001. Comparisons with other glaciated mountainous regions in western China show that glaciers in the research area have experienced less retreat. Based on records from the Guliya ice core, we believe that an increase in air temperature was the main forcing factor for glacier shrinkage during 1970–2001.

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.

Thinning and Shrinkage of Laohugou No. 12 Glacier in the Western Qilian Mountains, China, from 1957 to 2007

Landsat images, real-time kinematic GPS measurements, and topographic maps were used to determine changes in ice elevation, volume, and areal extent of the Laohugou No. 12 glacier (Qilian Mountains, China) between 1957 and 2007. The glacier experienced significant thinning and areal shrinkage in the ablation zone, but slight thickening in part of the accumulation zone. Elevation decreased by 18.6±5.4 m between 1957 and 2007 in the regions covered by the GPS measurements. The total volume loss for the entire glacier was estimated to be 0.218 km3 using a third-order polynomial fit method. The area diminished by 0.28 km2 between 1957 and 1994, 0.26 km2 between 1994 and 2000, and 0.28 km2 between 2000 and 2007, suggesting that the rate of loss in glacial coverage has increased since the mid-1990s. Significant increases in annual mean air temperature may have contributed to shrinkage and thinning of the glacier.

Peculiar phenomena regarding climatic and glacial variations on the Tibetan Plateau

Abstract In contrast to the worldwide intensive warming and consequent glacier shrinkage during the last 30 years, two peculiar phenomena have been observed on the Tibetan Plateau: (1) the temperature has decreased about 0.6˚C on the northern Tibetan Plateau, with smaller than average glacier retreat and meltwater discharge, and (2) a number of glaciers have been advancing on the southeast Tibetan Plateau in response to increased precipitation. These observations indicate the complex nature of the response of glaciers to climate changes.

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...

Mass loss from glaciers in the Chinese Altai Mountains between 1959 and 2008 revealed based on historical maps, SRTM, and ASTER images

Mass loss of glaciers in the Chinese Altai was detected using geodetic methods based on topographical maps (1959), the Shuttle Radar Topography Mission (SRTM) Digital Elevation Model (DEM) (2000), and the Advanced Space-borne Thermal Emission and Reflection Radiometer (ASTER) stereo images (2008). The results indicate that a continued and accelerating shrinkage has occurred in the Chinese Altai Mountains during the last 50 years, with mass deficits of 0.43 ± 0.02 and 0.54 ± 0.13 m a−1 water equivalent (w.e.) during the periods 1959–1999 and 1999–2008, respectively. Overall, the Chinese Altai Mountains have lost 7.06 ± 0.44 km3 in ice volume (equivalent to −0.43 ± 0.03 m a−1 w.e.) from 1959–2008. The spatial heterogeneity in mass loss was potentially affected by comprehensive changes in temperature and precipitation, and had a substantial correlation with glacier size and topographic settings. Comparison shows that in the Chinese Altai Mountains glaciers have experienced a more rapid mass loss than those in the Tianshan and northwestern Tibetan Plateau (TP), and the mass balance of glaciers was slightly less negative relative to those in the Russian Altai, Himalaya, and southern TP.

Accelerated thinning of Hei Valley No. 8 Glacier in the Tianshan Mountains, China

Two field surveys on the thickness of Hei Valley No. 8 Glacier (H8) on the southern slope of Mount Bogda in the Tianshan (天山) Mountains using ground-penetration radar (GPR) were carried out in August 2008 and September 2009. Comparisons of the observed change in glacier thickness using GPR and ablation stakes suggest that GPR observations have high accuracy. Thus, the thickness change for H8 during 2008–2009 was estimated using GPR data. Digital elevation models obtained from topographic maps and the Shuttle Radar Topography Mission were used to analyze ice-elevation changes of H8 between 1 969 and 2 000 m a.s.l.. The results show that H8 has continually thinned, and the thinning rate has increased gradually. The thinning of ablation areas of H8 increased from 0.42±0.56 m/a in 1969–2000 to 1.47±0.79 m/a in 2000–2008, and then accelerated to 1.92±0.98 m/a in 2008–2009. The retreat of the glacier terminus has had a similar pattern. The distribution of the temperate-ice zone of H8 as determined from GPR data also implies that H8 has experienced strong melting from 2008 to 2009, which indicates that temperature rises have not only enhanced glacial surface melting and prolonged melting periods, but also changed the englacial structure and increased the water content of glacier, both of which probably lead to the acceleration of glacial thinning.

Quick release of internal water storage in a glacier leads to underestimation of the hazard potential of glacial lake outburst floods from Lake Merzbacher in Central Tian Shan Mountains

Glacial meltwater and ice calving contribute to the flood volume of glacial lakes such as Lake Merzbacher in the Tian Shan Mountains of central Asia. In this study, we simulated the lakes volume by constructing an empirical relationship between the area of Lake Merzbacher, determined from satellite images, and the lakes water storage, derived from digital elevation models. Results showed that the lake water supply rate before Glacial Lake Outburst Floods (GLOFs) generally agreed well with those during the GLOFs from 2009 to 2012 but not in 2008 and 2015. Furthermore, we found that the combination of glacial meltwater and ice calving is not enough to fully explain the supply rate during GLOFs in 1996 and 1999, suggesting other factors affect the supply rate during GLOFs as well. To examine this further, we compared the water supply rate before and during GLOF events in 1999 and 2008. We inferred that quickly released short-term and intermediate-term water storage by glaciers have likely contributed to both flood events in those years. This study highlights the need to improve our understanding of the supply component of outburst floods, such as irregularly released stored water may lead to GLOF events with generally three different types: case I (singular event-triggered englacial water release), case II (glacier melt due to temperature changes), and case III (englacial water release mixed with glacier melt).