The Pleistocene Glaciation in the Karakoram Mountains:Reconstruction of Past Glacier Extensions and Ice Thicknesses

Geomorphological and Quaternarygeological field- and laboratory data (Fig.1) are introduced and interpreted with regard to the maximum Ice Age (LGM) glaciation of the Central-and South Karakoram in the Braldu-, Basna-, Shigar-and Indus valley system as well as on the Deosai plateau between the Skardu Basin and the Astor valley (Fig.2). These data result from two research expeditions in the years 1997 and 2000. They show that between c. 60 and 20 Ka the Central Karakorum and its south slope were covered by a continuous c. 125,000 km2 sized ice stream network. This ice stream network flowed together to a joint parent glacier, the Indus glacier. The tongue end of the Indus glacier reached down to 850 ～ 800 m a.s.l. In its centre the surface of this Indus ice stream network reached a height of a good 6000 m. Its most important ice thicknesses amounted to c. 2400 ～ 2900 m.

Ice thickness distribution and volume estimation of Burqin Glacier No.18 in the Chinese Altay Mountains

Information on the thickness distribution and volume of glacier ice is highly important for glaciological applications;however,detailed measurements of the ice thickness of many glaciers in the Chinese Altay Mountains remain lacking.Burqin Glacier No.18 is a northeast-orientated cirque glacier located on the southern side of the Altay Mountains.This study used PulseEKKO®PRO 100A enhancement ground-penetrating radar(GPR)to survey the ice thickness and volume of Burqin Glacier No.18 in summer 2018.Together with GPR surveying,spatial distributed profiles of the GPR measurements were concurrently surveyed using the real-time kinematic(RTK)global navigation satellite system(GNSS,Unistrong E650).Besides,we used QuickBird,WorldView-2,and Landsat TM to delineate accurate boundary of the glacier for undertaking estimation of glacier ice volume.GPR measurements revealed that the basal topography of profile B1-B2 was flat,the basal topography of profile C1-C2 presented a V-type form,and the basal topography of profile D1-D2 had a typical U-type topographic feature because the bedrock near the central elevation of the glacier was relatively flat.The longitudinal profile A1-A2 showed a ladder-like distribution.Glacier ice was thin at the terminus and its thickness increased gradually from the elevation of approximately 2620 m a.s.l.along the main axis of the glacier tongue with an average value of 80(±1)m.The average ice thickness of the glacier was determined as 27(±2)m and its total ice volume was estimated at 0.031(±0.002)km3.Interpretation of remote sensing images indicated that during 1989–2016,the glacier area reduced from 1.30 to 1.17 km2(reduction of 0.37%/a)and the glacier terminus retreated at the rate of 8.48 m/a.The mean ice thickness of Burqin Glacier No.18 was less than that of the majority of other observed glaciers in China,especially those in the Qilian Mountains and Central Chinese Tianshan Mountains;this is probably attributable to differences in glacier type and climatic setting.

Modeling ice thickness distribution and storage volume of glaciers in Chandra Basin,western Himalayas

This article reports modeled ice thickness distribution and total ice volume of the 65 selected glaciers(>0.5 km^2)of Chandra basin,located in the Western Himalayas.This is a first-of-its-kind study that gives detailed insights about the current ice thickness distribution at an individual glacier level in the Western Himalayas.The estimates are obtained using an optimally parameterized Glab Top2_IITB[Glacier Bed Topography Indian Institute of Technology Bombay(IITB)version]model with highresolution Digital Elevation Model(DEM)as an input.The total estimated volume of all the 65 selected glaciers is about 55.32 km^3 covering a total area of about 591.03 km^2.Using hypsometric analysis,it is found that the maximum amount of ice volume,i.e.,about 12.79 km^3,is currently residing at the elevation range of 5200–5400 m a.s.l.Ice thickness estimates obtained in the current study are compared with the ensemble estimates obtained in the Global Glacier Thickness Initiative(G2TI)project for three large glaciers,namely,Bada Shigri,Samudra Tapu,and Gepang Gath glaciers.The obtained results indicate that the difference between both the studies is marginal in terms of mean ice thickness and maximum ice thickness estimates except Samudra Tapu glacier.Moreover,the uncertainty of the estimated glacier ice volume from this study is about±15%whereas,from the G2TI project,it is about 25%.The main reasons for the difference could be the quality of the inputs used,model structure,model parameterization as well as the time stamp of the input used.The obtained results from this study indicate that the use of appropriate shape factor and better DEM would result in more reliable glacier ice thickness estimates even by using a simple slopedependent model like Glab Top2_IITB.

High-precision measurements of the inter-annual evolution for Urumqi Glacier No.1 in eastern Tien Shan,China

High-precision measuring of glacier evolution remains a challenge as the available global and regional remote sensing techniques cannot satisfactorily capture the local-scale processes of most small-and medium-sized mountain glaciers.In this study,we use a high-precision local remote sensing technique,long-range terrestrial laser scanning(TLS),to measure the evolution of Urumqi Glacier No.1 at an annual scale.We found that the dense point clouds derived from the TLS survey can be used to reconstruct glacier surface terrain,with certain details,such as depressions,debris-covered areas,and supra-glacial drainages can be distinguished.The glacier experienced pronounced thickness thinning and continuous retreat over the last four mass-balance years(2015−2019).The mean surface slope of Urumqi Glacier No.1 gradually steepened,which may increase the removal of glacier mass.The glacier was deeply incised by two very prominent primary supra-glacial rivers,and those rivers presented a widening trend.Extensive networks of supra-glacial channels had a significant impact on accelerated glacier mass loss.High-precision measuring is of vital importance to understanding the annual evolution of this type of glacier.

Estimation of glacier ice storage in western China constrained by field ground-penetrating Radar surveys

Recent decades have witnessed the accelerated retreat of alpine glaciers,which likely portends a decline in the glacial ice melt on which large downstream populations rely for freshwater.Thus,estimating water storage in alpine glaciers is critical for predicting the trend of glacier melting.This study compiled a rich set of ice thickness observations for glaciers of varying sizes in western China.We here presented a first-order assessment of the various errors involved in interpreting ice thickness from ground-penetrating radar(GPR)observations.An empirical Bayesian kriging(EBK)method was used for ice thickness interpolation and volume estimation.We then established a new volume-scaling law specific to western China glaciers based on these 36 volume-area pairs.And together with the Second Chinese Glacier Inventory(SCGI),we obtain a regional volume estimate of 4451±298 km^(3).By comparison,we believed that this result is the most reliable estimate of the total ice storage in western China and more reliably predicts gross glacier melting.However,our results show that the method of glacier division can strongly affect the total volume estimation,which previous studies ignored.This emphasizes the need for more surveyed glaciers data and more accurate glacier inventory to improve the evaluation of the climate impact on glacier melting water resources and to help ensure the future survival of these alpine glaciers.