Conference Agenda

Several decades of glacier recession has led to the formation of large populations of glacial lakes in most glacierised high mountain regions of the world. In many of these regions, enhanced glacier retreat and mass loss has been observed from glaciers which remain in contact with a glacial lake over a prolonged time period. Such negative glacier-lake interactions may heavily influence the long term ice mass loss budget of high mountain regions, and heighten the threat posed by glacial lake outburst floods (GLOFs). Glacier-lake interactions remain scarcely studied in the Himalaya, thus our aim of this work is to quantify the impact of lake expansion on glacier mass loss and glacier retreat across the main Himalayan arc. We generated geodetic mass balance estimates for two time periods (1970s-2000 and 2000-2016) over several regions of the main Himalayan arc, and observed 39-51% greater ice mass loss from lake-terminating glaciers when compared to land-terminating glaciers. Lake-terminating glaciers contributed ~19% of the total ice mass loss across the region, across both time periods, despite comprising only 9% of the glacier population. The mapping of glacier terminus positions over coincident periods shows land-terminating glacier retreat rates of 6.6-12.4 m a^-1, and 16.5-26 m a^-1 for lake-terminating glaciers. Over the later time period, land-terminating glacier length reduced by 8.5%, whereas lake-terminating glacier length reduced by 19.2%. Our results emphasise the role of lake expansion in glacier evolution across the Himalaya, and the requirement to consider glacier-lake interactions in future assessments of glacier recession in the region.

There are more than 5000 glacial lakes > 0.003 km² in the Third Pole region including the Pamir-Hindu Kush-Karakoram-Himalaya and the Tibetan Plateau. Around 30 lakes were identified as being potentially the most dangerous across the Tibetan Plateau. This assessment was based on four core determinates of GLOF hazard, including lake size, watershed area, dam steepness, and topographic potential for ice/rock avalanching. This study found that the potentially most dangerous lakes are located in the central Himalaya, the region where past glacial lake outburst floods (GLOFs) have occurred most frequently. Despite this fact, in-situ measurements relating to lake bathymetries, dam stability, and mother glacier dynamics are still very limited. We selected the most dangerous lakes in the central Himalaya (mainly in Poiqu basin), and mapped lake extents, glacier outlines, their frontal positions and ice flow from optical remote sensing data, and calculated glacier surface elevation change from digital terrain models between 1970s and 2018. Measurements of bathymetries, ground temperature, moisture and heat fluxes at different depths in the lake dam and outwash areas are ongoing. The stability of moraine dams, eventual failure and possible GLOF impacts will be modelled, and observations will be extended over long timescales. The glacial-lake change analysis presented in this study can significantly improve our knowledge of past lake evolution in the central Himalayas and the future GLOF threat.

Meltwater from rock glaciers could provide a relevant contribution to water supply especially in dry regions. Moreover, rock glaciers could have serious hazard potentials when located at or above steep slopes or when damming lakes. Existing investigations about rock glaciers in High Mountain Asia indicate that the landforms are abundant, but information is rare for the Tibetan Plateau and the northern slopes of the Himalaya.

We compiled a rock glacier inventory for the Poiqu basin (~28°17´N, 85°58´E) – central Himalaya/Tibet. The mapping was mainly based on optical Pleaides imagery with 0.5m resolution. Rock glaciers were identified based on their characteristic shape and their surface structure. In addition, we generated a Pleiades DEM and used it for a) creating a hillshade to support rock glacier identification and b) to derive their topographical parameters. Additional information on the occurrence and activity of the rock glaciers was provided by the InSAR technique using ALOS-1 data.

The results of the inventory reveal 370 rock glaciers covering an area of about 21.2 km². The largest one has an area of 0.5 km² and three have an area of more than 0.3 km². The rock glaciers are located between ~3715 m and ~5850 m with a mean altitude of ~5075 m a.s.l.. The mean slope of all rock glaciers is close to 17.4° (min. 6.8°, max. 37.6°). Most of the rock glaciers face towards the Northeast (19%) and West (18.5%). Our study indicates that 147 rock glaciers can be classified as active. We also found rock glaciers damming lakes and rock glaciers located above roads which could threaten the infrastructure in case of instability.

Preliminary results of rock glacier mapping of the same region, which were based on Sentinel 2 images with 10 m resolution and the 8 m High Mountain Asia DEM revealed slightly less rock glaciers (362) in numbers and but indicated a much larger rock glacier area (>40 km²). We conclude, that high resolution data is of utmost importance when creating a rock glacier inventory.

Active rock glaciers (ARGs) and protalus lobes (PTLs) are characteristic periglacial landforms indicating the presence and creeping process of permafrost underground in an alpine environment. However, little information about such landforms has been provided in mountainous western China. In this work, we compiled an inventory including ARGs and PTLs in part of the West Kunlun Shan based on satellite Synthetic Aperture Radar (SAR) interferometry and optical images from Google Earth. Fifteen interferograms generated from ALOS-1 PALSAR images were used for identifying ground movements. Their geomorphic parameters such as aspect, area, altitude, and slope angle, were quantified using the SRTM digital elevation model. Within the 70000 km² study area, we identified 67 ARGs and 22 PTLs. The preliminary results reveal that the mean downslope velocities of the ARGs and PTLs are 79 cm/yr and 25 cm/yr, respectively. The maximum downslope velocity for the ARGs is about 200 cm/yr. The aspects of the landforms vary significantly: 45% of the ARGs are located on northeast-facing slopes while 50% of the PTLs are located on southeast-facing slopes. Our inventory shows the total areas covered by ARGs and PTLs are 14.4 km² and 1.2 km², respectively. The largest ARG has an area of 0.7 km². The ARGs are located between 4100 m and 5600 m and have a mean slope angle of 13°. While the PTLs are in a narrower band, between 4600 m and 5300 m and have a slightly steeper angle of 18°.Compared with the existing rock glacier inventories in High Mountain Asia such as the northern Tien Shan and the Hindu Kush Himalaya, the distribution density of ARGs and PTLs in the western Kunlun Shan is much lower.