Tino Pieczonka

Planimetric and volumetric glacier changes in the Khumbu Himal, Nepal, since 1962 using Corona, Landsat TM and ASTER data

Multitemporal space imagery from 1962 (Corona KH-4), 1992 (Landsat TM), 2001 and 2005 (Terra ASTER) was used to investigate the glacier changes in the Khumbu Himal, Nepal. The ice coverage in the investigation area decreased by about 5% between 1962 and 2005, with the highest retreat rates occurring between 1992 and 2001. The debris coverage increased concomitantly with the decrease in total glacier area. The clean-ice area decreased by >10%. Digital terrain model (DTM) generation from the early Corona KH-4 stereo data in this high-relief terrain is time-consuming, and the results still contain some elevation errors. However, these are minor in the snow-free areas with gentle slopes. Thus comparison of the surfaces of the debris-covered glacier tongues based on the Corona DTM and an ASTER DTM is feasible and shows the downwasting of the debris-covered glaciers. The highest downwasting rates, more than 20 m (>0.5 m a -1 ), can be found near the transition zone between the active and the stagnant glacier parts of the debris-covered glacier tongues. The downwasting is lower, but still evident, in the active ice areas and at the snout with thick debris cover. All investigated debris- covered glaciers in the study area show similar behaviour. The estimated volume loss for the investigated debris-covered glacier tongues is 0.19 km 3 .

Attribution of streamflow trends in snow and glacier melt-dominated catchments of the Tarim River, Central Asia

Observed streamflow of headwater catchments of the Tarim River (Central Asia) increased by about 30% over the period 1957–2004. This study aims at assessing to which extent these streamflow trends can be attributed to changes in air temperature or precipitation. The analysis includes a data-based approach using multiple linear regression and a simulation-based approach using a hydrological model. The hydrological model considers changes in both glacier area and surface elevation. It was calibrated using a multiobjective optimization algorithm with calibration criteria based on glacier mass balance and daily and interannual variations of discharge. The individual contributions to the overall streamflow trends from changes in glacier geometry, temperature, and precipitation were assessed using simulation experiments with a constant glacier geometry and with detrended temperature and precipitation time series. The results showed that the observed changes in streamflow were consistent with the changes in temperature and precipitation. In the Sari-Djaz catchment, increasing temperatures and related increase of glacier melt were identified as the dominant driver, while in the Kakshaal catchment, both increasing temperatures and increasing precipitation played a major role. Comparing the two approaches, an advantage of the simulation-based approach is the fact that it is based on process-based relationships implemented in the hydrological model instead of statistical links in the regression model. However, data-based approaches are less affected by model parameter and structural uncertainties and typically fast to apply. A complementary application of both approaches is recommended.

Surge-Type Glaciers in the Tien Shan (Central Asia)

ABSTRACT Surge-type glaciers have been observed in several mountain ranges of the world. Though Karakoram and Pamir are the hot spots for the occurrence of surge-type glaciers in High Mountain Asia, few surge-type glaciers also exist in Tien Shan. These have not been studied or reported in detail in the recent literature. We have identified 39 surge-type glaciers and five tributary surges in Tien Shan either from available literature or by visual interpretation using available images from the period 1960 until 2014. Out of the 39 glaciers, 9 are confirmed as surge-type, 13 are very probably surge-type, and the remaining are possibly of surge-type. Most of the surge-type glaciers are located in Ak-Shiirak and Central Tien Shan. Compared with the normal glaciers of Tien Shan, the surge-type glaciers are larger, cover higher ranges of elevations, and have shallower slopes. There is no significant difference in aspect. The largest surge events were observed in Central Tien Shan: North Inylchek Glacier (years 1996/1997) and Samoilowich Glacier (years 1992 until 2006) advanced several kilometers. The surge cycle was around 50 years for both of these glaciers. The advance was less pronounced for all other surge-type glaciers during the period ca. 1960–2014. Some of the tributary glaciers behaved differently than the main glaciers in the sense that they continuously advanced during the entire period of our study, whereas the main glaciers have remained stable or retreated.

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).