No abstract

Earth observation offers a variety of techniques for monitoring and characterizing geomorphic processes in high mountain environments. Terrestrial laserscanning and unmanned aerial vehicles provide very high resolution data with high accuracy. Automatic cameras have become a valuable source of information—mostly in a qualitative manner—in recent years. The availability of satellite data with very high revisiting time has gained momentum through the European Space Agency’s Sentinel missions, offering new application potential for Earth observation. This paper reviews the status of recent techniques such as terrestrial laserscanning, remote sensed imagery, and synthetic aperture radar in monitoring high mountain environments with a particular focus on the impact of new platforms such as Sentinel-1 and -2 as well as unmanned aerial vehicles. The study area comprises the high mountain glacial environment at the Pasterze Glacier, Austria. The area is characterized by a highly dynamic geomorphological evolution and by being subject to intensive scientific research as well as long-term monitoring. We primarily evaluate landform classification and process characterization for: (i) the proglacial lake; (ii) icebergs; (iii) the glacier river; (iv) valley-bottom processes; (v) slope processes; and (vi) rock wall processes. We focus on assessing the potential of every single method both in spatial and temporal resolution in characterizing different geomorphic processes. Examples of the individual techniques are evaluated qualitatively and quantitatively in the context of: (i) morphometric analysis; (ii) applicability in high alpine regions; and (iii) comparability of the methods among themselves. The final frame of this article includes considerations on scale dependent process detectability and characterization potentials of these Earth observation methods, along with strengths and limitations in applying these methods in high alpine regions.

Abstract. The formation and development of glacial lakes in mountainous regions is one of the consequences of glacier recession. Such lakes may drain partially or completely when the stability of their dams is disturbed or as a consequence of impacts. We present a case study from the Central Asian mountain range of Tien Shan – a north-oriented tributary of the Adygine Valley, where the retreat of a polythermal glacier surrounded by permafrost has resulted in the formation of several generations of lakes. The aim of this study was to analyse the past development of different types of glacial lakes influenced by the same glacier, to project the site's future development, and to evaluate the outburst susceptibility of individual lakes with an outlook for expected future change. We addressed the problem using a combination of methods, namely bathymetric, geodetic and geophysical on-site surveys, satellite images and digital elevation model analysis, and modelling of glacier development. Based on this case of the glacial lakes being of varied age and type, we demonstrated the significance of glacier ice in lake development. Lake 3, which is in contact with the glacier terminus, has changed rapidly over the last decade, expanding both in area and depth and increasing its volume by more than 13 times (7800 to 106 000 m3). The hydrological connections and routing of glacier meltwater have proved to be an important factor as well, since most lakes in the region are drained by subsurface channels. As the site is at the boundary between continuous and discontinuous permafrost, the subsurface water flow is strongly governed by the distribution of non-frozen zones above, within, or beneath the perennially frozen ground. In the evaluation of lake outburst susceptibility, we have highlighted the importance of field data, which can provide crucial information on lake stability. In our case, an understanding of the hydrological system at the site, and its regime, helped to categorise Lake 2 as having low outburst susceptibility, while Lake 1 and Lake 3 were labelled as lakes with medium outburst susceptibility. Further development of the site will be driven mainly by rising air temperatures and increasingly negative glacier mass balance. All three climate model scenarios predicted a significant glacier areal decrease by 2050, specifically leaving 73.2 % (A1B), 62.3 % (A2), and 55.6 % (B1) of the extent of the glacier in 2012. The glacier retreat will be accompanied by changes in glacier runoff, with the first peak expected around 2020, and the formation of additional lakes.

Surface state data derived from spaceborne microwave sensors with suitable temporal sampling are to date only available in low spatial resolution (25-50 km). Current approaches do not adequately resolve spatial heterogeneity in landscape-scale freeze-thaw processes. We propose to derive a frozen fraction instead of binary freeze-thaw information. This introduces the possibility to monitor the gradual freezing and thawing of complex landscapes. Frozen fractions were retrieved from Advanced Scatterometer (ASCAT, C-band) backscatter on a 12.5-km grid for three sites in noncontinuous permafrost areas in northern Finland and the Austrian Alps. To calibrate the retrieval approach, frozen fractions based on Sentinel-1 synthetic aperture radar (SAR, C-band) were derived for all sites and compared to ASCAT backscatter. We found strong relationships for ASCAT backscatter with Sentinel-1 derived frozen fractions (Pearson correlations of −0.85 to −0.96) for the sites in northern Finland and less strong relationships for the Alpine site (Pearson correlations −0.579 and −0.611, including and excluding forested areas). Applying the derived linear relationships, predicted frozen fractions using ASCAT backscatter values showed root mean square error (RMSE) values between 7.26% and 16.87% when compared with Sentinel-1 frozen fractions. The validation of

Abstract. Formation and development of glacial lakes in mountain regions is one of the consequences of glacier recession. 10Such lakes may drain partially or completely when the stability of their dam is disturbed. We presented a case study from Central-Asian mountain range of Tien Shan, a north-oriented tributary valley Adygine, where a glacier retreat resulted in formation of several generations of lakes. The aim of this study was to analyse past development of different types of glacial lakes influenced by the same glacier, to project site's future development, and to evaluate the hazard of individual lakes with an outlook for expected future change. We addressed the problem with a combination of methods, namely bathymetric, 15 geodetic, and geophysical on-site survey, satellite image and DEM analysis, and modelling of glacier runoff evolution. Based on the case of glacial lakes of varied age and type, we demonstrate the significance of glacier ice in lake's development. Lake 3, which is in contact with glacier terminus, has changed rapidly over the last decade, expanding both in area and depth and increasing its volume more than 13 times (7 800 m 3 to 106 000 m 3 ). Hydrological connections and routing of glacier meltwater proved to be an important factor as well, since most lakes in the region are drained by subsurface channels. Within the hazard 20 evaluation of lakes, we highlighted the importance of field data which can provide crucial information on lake stability. In our case, the understanding of site's hydrological system and its regime helped to categorise Lake 2 into low outburst hazard, while Lake 1 and Lake 3 were labelled as medium hazard lakes. Further development of the site will be driven mainly by rising air temperature and increasingly negative glacier mass balance. All three scenarios predict a significant glacier area decrease by 2050, specifically leaving 73.2 % (A1B), 62.3 % (A2), and 55.6 % (B1) of the 2012 glacier extent. The glacier retreat will be 25 accompanied by changes in glacier runoff with first peak expected around the year 2020.

Abstract. Global warming and glacier retreat are affecting the morphodynamics of proglacial rivers. In response to changing hydrology, their altered hydraulics will significantly impact future glacifluvial erosion and proglacial channel development. This study analysis proglacial channel evolution processes at the foreland of Austria’s biggest glacier Pasterze by predicted runoff until 2050. A high-resolution digital elevation model was created by an unmanned aerial vehicle, channel bathymetry was sampled, a one-dimensional hydrodynamic-numerical model was generated, and bedload transport formulas were used to calculate the predicted transport capacity of the proglacial river. Due to the fine sediment composition near the glacier terminus (d50 < 49.6 mm), the calculation results underline the process of headward erosion in the still unaffected, recently deglaciated river section. In contrast, an armor layer is already partly established by the coarse grain size distribution in the already incised river section (d50 > 201 mm). Furthermore, already occurring exposed non-fluvial grain sizes combined with decreasing flow competence in the long term are indicators for erosion-resistant pavement layer formation and landform decoupling in the vertical direction. The presented study clearly shows that subsystems of ‘developed channels’ exhibiting pavement formation of non-fluvial deposits are found at the investigated glacier foreland. Thus, an extension accompanied by a refinement of the fluvial system in the sediment cascade approach was developed as a central result.

&lt;p&gt;Spatially distributed winter snow accumulation over glaciers is an important information for a lot of purposes. Typically, snow depth on glaciers is measured by manual snow probing or ground penetrating radar. The point measurements of snow depth and snow density are then used to calculate the winter mass balance of the glacier.&lt;/p&gt;&lt;p&gt;In the last decade remote sensing techniques such as LIDAR and structure from motion (sfm) photogrammetry in combination with unmanned aerial vehicles (UAVs) have become more frequent to reconstruct snow surfaces providing a better spatial coverage and spatial resolution. Snow depth is calculated by DEM differencing of a No-Snow surface (summer surface) and the snow surface (winter surface).&lt;/p&gt;&lt;p&gt;However, using DEM differencing to extract snow depth over glaciers introduces the problem, that the No-Snow surface is not constant, as (1) the glacier is moving between the survey dates and (2) the surface possibly undergoes surface lowering due to melt after the summer survey.&lt;/p&gt;&lt;p&gt;In this study we present measurements on two small mass balance glaciers in the Austrian Alps (Goldbergkees and Kleinflei&amp;#223;kees). We account for the evolution of the No-Snow surface by (1) applying a simple model of the vertical ice movement and by (2) calculating the surface lowering due to melt using a distributed mass balance model. &amp;#160;The effect of both corrections is then validated using a dense network of manual snow depth measurements across the glacier.&lt;/p&gt;