Glacier mass loss during the 1960s and 1970s in the Ak-Shirak range (Kyrgyzstan) from multiple stereoscopic Corona and Hexagon imagery

This study was conducted within the framework of the project “Spaceborne glacier monitoring of the Aksu-Tarim catchment (Xinjiang/China, Kyrgyzstan)” funded by Deutsche Forschungsgemeinschaft (DFG, Code BO 3199/2-1) and the Glaciers_cci project funded by the European Space Agency (ESA through grant4000109873/14/I-NB).Comprehensive research on glacier changes in the Tian Shan is available for the current decade; however, there is limited information about glacier investigations of previous decades and especially before the mid 1970s. The earliest stereo images from the Corona missions were acquired in the 1960s but existing studies dealing with these images focus on single glaciers or small areas only. We developed a workflow to generate digital terrain models (DTMs) and orthophotos from 1964 Corona KH-4 for an entire mountain range (Ak-Shirak) located in the Central Tian Shan. From these DTMs and orthoimages, we calculated geodetic mass balances and length changes in comparison to 1973 and 1980 Hexagon KH-9 data. We found mass budgets between -0.4 ± 0.1 m·w.e.a -1 (1964-1980) and -0.9 ± 0.4 m·w.e.a -1 (1973-1980) for the whole region and individual glaciers. The length changes, on the other hand, vary heterogeneously between +624 ± 18 m (+39.0 ± 1.1 m.a -1 ) and -923 ± 18 m (-57.7 ± 1.1 m·a -1 ) for 1964-1980. An automation of the processing line can successively lead to region-wide Corona data processing allowing the analysis and interpretation of glacier changes on a larger scale and supporting a refinement of glacier modelling.Publisher PDFPeer reviewe

Brief communication : Glaciers in the Hunza catchment (Karakoram) have been nearly in balance since the 1970s

Previous geodetic estimates of mass changes in the Karakoram revealed balanced budgets or a possible slight mass gain since ∼2000. Indications of longer-term stability exist but only very few mass budget analyses are available before 2000. Here, based on 1973 Hexagon KH-9, ∼2009 ASTER and the SRTM DTM, we show that glaciers in the Hunza River basin (central Karakoram) were on average in balance or showed slight insignificant mass loss within the period ∼1973-2009. Heterogeneous behaviour and frequent surge activities were also characteristic of the period before 2000. Surge-type and non-surge-type glaciers showed on average no significantly different mass change values. However, some individual glacier mass change rates differed significantly for the periods before and after ∼2000.Publisher PDFPeer reviewe

Glacier branch lines and glacier ice thickness estimation for debris-covered glaciers in the Central Tien Shan

Information about the ice volume stored in glaciers is of high importance for sustainable water management in many arid regions of Central Asia. Several methods to estimate the ice volume exist. However, none of them take the specific characteristics of flat terminus debris-covered glaciers into account. We present a method for deriving spatially-distributed ice thickness for debris-covered dendritic glaciers, which are common not only in Central Tien Shan but also in several other mountain ranges in High Asia. The method relies on automatically generated branch lines, observed surface velocities and surface topographic parameters as basic input. Branch lines were generated using Thiessen polygons and Dijkstra's path algorithm. Ice thicknesses for four debris-covered glaciers - South Inylchek, Kaindy, Tomur and Koxkar glaciers - have been estimated along the branch line network solving the equation of laminar flow. For Koxkar and South Inylchek glaciers, respectively, maximum thicknesses of 250 and 380 m were estimated. These results differ by 50 m compared with GPR measurements with an uncertainty for the debris-covered parts of 40%. Based on geodetic mass balances, we estimate that the investigated glaciers lost between 6 and 28% of their volume from 1975 to the early 2000s.Publisher PDFPeer reviewe

Area and mass changes of Siachen Glacier (East Karakoram)

The authors thank the European Space Agency for providing the Envisat data under the AOE 668 project. T. Bolch and T. Strozzi acknowledge funding by the European Space Agency (ESA) within the Glaciers_cci project (code 4000109873/14/I-NB).Here, we present a comprehensive assessment of Siachen Glacier (East Karakoram), in terms of its area and elevation change, velocity variations and mass budget, utilizing different satellite datasets including Landsat, Hexagon, Cartosat-I, Shuttle Radar Topography Mission, Envisat Advanced Synthetic Aperture Radar and Japanese Advanced Land Observing Satellite Phased Array-type L-band SAR. The total areal extent of Siachen Glacier did not change significantly between 1980 and 2014; however the exposed-ice area decreased during that period. The terminus of the glacier has experienced substantial downwasting (on average 30 m) over the period of 1999-2007, followed by a retreat of the transition between exposed and debris-covered ice by a distance of 1.3 km during the short span 2007-14. The spatial patterns of the elevation difference and velocity are heterogeneous over the large areal extent of Siachen Glacier. The average velocity of the entire glacier, as computed between 11 December 2008 and 26 January 2009, was 12.3 ± 0.4 cm d -1 , while those estimated separately for the accumulation and ablation regions were 9.7 ± 0.4 cm d -1 and 20.4 ± 0.4 cm d -1 , respectively. The mass budget of Siachen Glacier is estimated to be -0.03 ± 0.21 m w.e. a -1 for the period of 1999-2007.Publisher PDFPeer reviewe

Overall recession and mass budget of Gangotri Glacier, Garhwal Himalayas, from 1965 to 2015 using remote sensing data

Thinning rates for the debris-covered Gangotri Glacier and its tributary glaciers during the period 1968-2014, length variation and area vacated at the snout from 1965 to 2015, and seasonal variation of ice-surface velocity for the last two decades have been investigated in this study. It was found that the mass loss of Gangotri and its tributary glaciers was slightly less than those reported for other debris-covered glaciers in the Himalayan regions. The average velocity during 2006-14 decreased by ~6.7% as compared with that during 1993-2006. The debris-covered area of the main trunk of Gangotri Glacier increased significantly from 1965 until 2015 with the maximum rate of increase (0.8 ± 0.2 km2 a-1) during 2006-15. The retreat (~9.0 ± 3.5 m a-1) was less in recent years (2006-2015) but the down-wasting (0.34 ± 0.2 m a-1) in the same period (2006-2014) was higher than that (0.20 ± 0.1 m a-1) during 1968-2006. The study reinforced the established fact that the glacier length change is a delayed response to climate change and, in addition, is affected by debris cover, whereas glacier mass balance is a more direct and immediate response. Therefore, it is recommended to study the glacier mass balance and not only the glacier extent, to conclude about a glacier's response to climate change.Publisher PDFPeer reviewe

Future climate change and its impact on runoff generation from the debris-covered Inylchek glaciers, central Tian Shan, Kyrgyzstan

The heavily debris-covered Inylchek glaciers in the central Tian Shan are the largest glacier system in the Tarim catchment. It is assumed that almost 50% of the discharge of Tarim River are provided by glaciers. For this reason, climatic changes, and thus changes in glacier mass balance and glacier discharge are of high impact for the whole region. In this study, a conceptual hydrological model able to incorporate discharge from debris-covered glacier areas is presented. To simulate glacier melt and subsequent runoff in the past (1970/1971-1999/2000) and future (2070/2071-2099/2100), meteorological input data were generated based on ECHAM5/MPI-OM1 global climate model projections. The hydrological model HBV-LMU was calibrated by an automatic calibration algorithm using runoff and snow cover information as objective functions. Manual fine-tuning was performed to avoid unrealistic results for glacier mass balance. The simulations show that annual runoff sums will increase significantly under future climate conditions. A sensitivity analysis revealed that total runoff does not decrease until the glacier area is reduced by 43%. Ice melt is the major runoff source in the recent past, and its contribution will even increase in the coming decades. Seasonal changes reveal a trend towards enhanced melt in spring, but a change from a glacial-nival to a nival-pluvial runoff regime will not be reached until the end of this century.Publisher PDFPeer reviewe