Detecting interannual and seasonal variability in rock glacier movement using a feature tracking approach

Permafrost degradation induces changes in water availability and runoff as well as slope instabilities in alpine regions. A thorough quantification of the degradational processes is therefore important for society in the immediate region and beyond, as it helps deepening our understanding and ultimately allows anticipating future trajectories of the alpine cryosphere. However, permafrost being an underground phenomenon makes quantification and temporal differentiation of the degradation processes inherently difficult. Active rock glaciers have become a prime research object as internal permafrost degradation induces changes in their kinematic behaviour. In our study, we investigate the surface kinematics of the Kaiserberg rock glacier in the Austrian Kaunertal on different timescales. To derive interannual surface displacement rates, we rely on UAV-derived digital topography from 2019-2022. In addition, we installed a time-lapse camera that records daily images of the rock glacier in July 2022 to resolve rock glacier movement at a higher temporal resolution. For both data sets, we use a feature-tracking approach as implemented in the environmental motion tracking software EMT. Preliminary results show differentiated velocity fields on the rock glacier surface with the southern lobe moving significantly faster than the larger northern lobe. Mean movement rates (2019- 2022) are around 0.58 m yr-1 for the southern lobe where maximum movement rates range up to 1.80 m yr-1. In contrast, mean movement rates for the northern lobe are only 0.1 m yr-1 with maximum rates of 0.36 m yr-1. Similar to earlier studies, we find a general increase in surface velocities over the past years that points to ongoing permafrost degradation. The pending analysis of the daily time lapse photos will provide an insight into how much of the annual movement occurs in summer and how the kinematics vary within a single season. As the timing of data acquisition varied each year, this knowledge can then also be used to refine the interpretation of interannual movement rates.Fil: Rehn, Lisa. Albert Ludwigs University of Freiburg; AlemaniaFil: Tapia Baldis, Carla Cintia. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mendoza. Instituto Argentino de Nivología, Glaciología y Ciencias Ambientales. Provincia de Mendoza. Instituto Argentino de Nivología, Glaciología y Ciencias Ambientales. Universidad Nacional de Cuyo. Instituto Argentino de Nivología, Glaciología y Ciencias Ambientales; ArgentinaFil: Blöthe, Jan Henrick. Albert Ludwigs University of Freiburg; AlemaniaMid-European Geomorphology MeetingSalzburgSuizaSalzburg UniversityGeoresearchTechnische Universität Münche

Pristine levels of suspended sediment in large German river channels during the Anthropocene?

Suspended sediment is an integral part of riverine transport and functioning that has been strongly altered during the Anthropocene due to the overwhelming human pressure on soils, sediments, and the water cycle. Understanding the controls of changing suspended sediment in rivers is therefore vital for effective management strategies. Here we present results from a trend analysis of suspended sediments covering 62 monitoring stations along the German waterways (catchment sizes range between 2000 and 160 000 km2) with more than 440 000 water samples taken between 1990 and 2010. Based on daily monitoring of suspended sediment concentration (SSC), we found significant declines in mean annual SSC and annual suspended sediment loads (SSLs) at 49 of 62 monitoring stations totaling −0.92 mg L−1 yr−1. At some stations decreases during the 20 years represent up to 50 % of the long-term average SSC. Significant decreases in SSC are associated with declining SSL despite an increase in sheet and rill erosion by almost 150 % derived from modeling due to changes in land use and management as well as rainfall erosivity. The contemporary suspended sediment loads of the Rhine at the German–Dutch border are approaching the natural base level of ∼1 Mt yr−1, which was reached by the Rhine during the mid-Holocene when the suspended sediment load was adjusted to the Holocene climatic conditions and before the onset of increased loads due to human-induced land use changes in the Rhine catchment. At this point we can only speculate regarding potential reasons for a decline in sediment transport in larger rivers despite erosion increase. We argue that increased sediment retention in upstream headwaters is presumably the major reason for declining SSC in the large river channels studied.</p

Ice content and interannual water storage changes of an active rock glacier in the dry Andes of Argentina

The quantification of volumetric ice and water contents in active rock glaciers is necessary to estimate their role as water stores and contributors to runoff in dry mountain catchments. In the semi-arid to arid Andes of Argentina, active rock glaciers potentially constitute important water reservoirs due to their widespread distribution. Here however, water storage capacities and their interannual changes have so far escaped quantification in detailed field studies. Volumetric ice and water contents were quantified using a petrophysical four-phase model (4PM) based on complementary electrical resistivities (ERT) and seismic refraction tomographies (SRT) in different positions of Dos Lenguas rock glacier in the Upper Agua Negra basin, Argentina. We derived vertical and horizontal surface changes of the Dos Lenguas rock glacier, for the periods 2016?17 and 2017?18 using drone-derived digital elevation models (DEM). Interannual water storage changes of −36 mm yr−1 and +27 mm yr−1 derived from DEMs of Difference (DoD) for the periods 2016?17 and 2017?18, respectively, indicate that significant amounts of annual precipitation rates can be stored in and released from the active rock glacier. Heterogeneous ice and water contents show ice-rich permafrost and supra-, intra- and sub-permafrost aquifers in the subsurface. Active layer and ice-rich permafrost control traps and pathways of shallow ground water, and thus regulate interannual storage changes and water releases from the active rock glacier in the dry mountain catchment. The ice content of 1.7?2.0 × 109 kg in the active Dos Lenguas rock glacier represents an important long-term ice reservoir, just like other ground ice deposits in the vicinity, if compared to surface ice that covers less than 3 % of the high mountain catchment.Fil: Halla, Christian. Universitat Bonn; AlemaniaFil: Blöthe, Jan Henrick. Universitat Bonn; AlemaniaFil: Tapia Baldis, Carla Cintia. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mendoza. Instituto Argentino de Nivología, Glaciología y Ciencias Ambientales. Provincia de Mendoza. Instituto Argentino de Nivología, Glaciología y Ciencias Ambientales. Universidad Nacional de Cuyo. Instituto Argentino de Nivología, Glaciología y Ciencias Ambientales; ArgentinaFil: Trombotto, Dario Tomas. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mendoza. Instituto Argentino de Nivología, Glaciología y Ciencias Ambientales. Provincia de Mendoza. Instituto Argentino de Nivología, Glaciología y Ciencias Ambientales. Universidad Nacional de Cuyo. Instituto Argentino de Nivología, Glaciología y Ciencias Ambientales; ArgentinaFil: Hilbich, Christin. University Of Fribourg; AlemaniaFil: Hauck, Christian. University Of Fribourg; AlemaniaFil: Schrott, Lothar. Universitat Bonn; Alemani

Erdoberflächenprozesse im Hochgebirge – Der Einfluss des Klimawandels

Der Einfluss des Klimawandels auf Erdoberflächenprozesse zeigt sich im Hochgebirge in vielfältiger Weise, ist jedoch hinsichtlich der kurz-, mittel- und langfristigen Auswirkungen bislang nicht allumfassend untersucht. Neben den klimatischen Einflussfaktoren kommen auch die veränderte Landnutzung durch den Menschen oder systeminterne Faktoren (z.B. Klüfte im Fels) zum Tragen. Zählen besonders kleine Gletscher (< 4 km²) zu geeigneten Klimaindikatoren, weil sie auf klimatische Veränderungen schnell durch sichtbare Längenänderungen reagieren, sind Auswirkungen an Berghängen oder in Felswänden im Gebirgspermafrost oft erst nach Jahren oder mit aufwändiger und präziser Messtechnik nachzuweisen und können häufig nicht ausschließlich auf den Klimawandel zurückgeführt werden. Dennoch gibt es Anzeichen dafür, dass viele Prozesse im Hochgebirge sowohl in der Häufigkeit des Auftretens als auch in ihrer Intensität zunehmen und somit zu tiefgreifenden Veränderungen und neuen Gefahren und Risiken führen werden. Der folgende Beitrag zeigt exemplarisch den Einfluss des Klimawandels auf die geomorphologische Wirkung von gravitativen Massenbewegungen, Schneelawinen, periglazialen, glazialen und fluvialen Prozessen im Hochgebirge. Earth surface processes in high mountain regions – the influence of climate change: The impact of climate change on earth surface processes in mountain systems can be observed in many ways, however, our knowledge regarding short-, medium-, and long-term effects is still limited. In addition to climatic factors, changes in land use or internal factors (e.g. fissures in rock) need to be considered as well. While small glaciers (< 4 km²) are very good indicators for climatic variations showing dramatic changes in lengths and volume, impacts on mountain slopes or on rock walls under permafrost conditions are much more difficult to identify, sometimes after years or only with sophisticated measurement techniques, and not always related to climate warming. Nevertheless, there is evidence that many processes in mountain areas do increase in frequency of occurrence and in magnitude which will cause profound changes with new hazards and risks. The following chapter exemplifies how climate changes affects various geomorphological processes, such as gravitational mass movements, avalanches, periglacial, glacial and fluvial processes in high mountains

Sediment rating and annual cycles of suspended sediment in German upland rivers

Sediment flux of lowland rivers is dominated by suspended transport, but data is often sparse and analysis largely relies on rating relationships. However, suspended sediment concentration is by no means constant in both, space and time. Here we analyse the variability of sediment rating curves and the seasonality of suspended sediment concentration in German waterways, as recorded by 10 gauging stations with catchment areas between 2600 - 22000 km2. Our data reveal a distinct break in power-law scaling relationships for all stations, with increased scaling exponents above threshold discharges close to the geometric mean. We attribute this mainly to the activation of sediment sources that resist mobilisation at lower flows. Furthermore, all stations show a counter-clockwise hysteresis effect throughout the year, where summer discharges have a higher sediment load than comparable winter discharges. Though the reasons for this pattern need further investigation, preliminary results show a strong correlation with rainfall erosivity and land-use parameters

Permafrost in den argentinischen Anden, ein bedeutender Wasserspeicher

Die semi-ariden Zentralanden Argentiniens werden durch eine weitfl ächige erbreitung von Permafrost und eine große vertikale Erstreckung von periglazialen Formen und Prozessen charakterisiert. Große Blockgletscherkomplexe mit eisreichem Permafrost werden in den Trockengebieten der Anden als bedeutende Wasserspeicher für die Zukunft angesehen. Die argentinische Regierung hat 2010 ein Gesetz zum Schutz der Gletscher und der periglazialen Höhenstufe erlassen, um diese Naturressourcen zu schützen. Die vorliegende Studie hat das Ziel, die Verbreitung der Blockgletscher aufzuzeigen und die wenig bekannten Eisgehalte dieser Periglazialformen zu quantifi zieren.Fil: Christian Halla. Universitat Bonn; AlemaniaFil: Jan Henrik Blöthe. Universitat Bonn; AlemaniaFil: Trombotto, Dario Tomas. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mendoza. Instituto Argentino de Nivología, Glaciología y Ciencias Ambientales. Provincia de Mendoza. Instituto Argentino de Nivología, Glaciología y Ciencias Ambientales. Universidad Nacional de Cuyo. Instituto Argentino de Nivología, Glaciología y Ciencias Ambientales; ArgentinaFil: Lothar Schrott. Universitat Bonn; Alemani

Deciphering Small-Scale Seasonal Surface Dynamics of Rock Glaciers in the Central European Alps Using DInSAR Time Series

The Essential Climate Variable (ECV) Permafrost is currently undergoing strong changes due to rising ground and air temperatures. Surface movement, forming characteristic landforms such as rock glaciers, is one key indicator for mountain permafrost. Monitoring this movement can indicate ongoing changes in permafrost; therefore, rock glacier velocity (RGV) has recently been added as an ECV product. Despite the increased understanding of rock glacier dynamics in recent years, most observations are either limited in terms of the spatial coverage or temporal resolution. According to recent studies, Sentinel-1 (C-band) Differential SAR Interferometry (DInSAR) has potential for monitoring RGVs at high spatial and temporal resolutions. However, the suitability of DInSAR for the detection of heterogeneous small-scale spatial patterns of rock glacier velocities was never at the center of these studies. We address this shortcoming by generating and analyzing Sentinel-1 DInSAR time series over five years to detect small-scale displacement patterns of five high alpine permafrost environments located in the Central European Alps on a weekly basis at a range of a few millimeters. Our approach is based on a semi-automated procedure using open-source programs (SNAP, pyrate) and provides East-West displacement and elevation change with a ground sampling distance of 5 m. Comparison with annual movement derived from orthophotos and unpiloted aerial vehicle (UAV) data shows that DInSAR covers about one third of the total movement, which represents the proportion of the year suited for DInSAR, and shows good spatial agreement (Pearson R: 0.42–0.74, RMSE: 4.7–11.6 cm/a) except for areas with phase unwrapping errors. Moreover, the DInSAR time series unveils spatio-temporal variations and distinct seasonal movement dynamics related to different drivers and processes as well as internal structures. Combining our approach with in situ observations could help to achieve a more holistic understanding of rock glacier dynamics and to assess the future evolution of permafrost under changing climatic conditions

Identifying mountain permafrost degradation by repeating historical electrical resistivity tomography (ERT) measurements

Ongoing global warming intensifies the degradation of permafrost. Permafrost thawing impacts landform evolution, reduces freshwater resources, enhances the potential of natural hazards and thus has significant socio-economic impacts. Electrical resistivity tomography (ERT) has been widely used to map the ice-containing permafrost by its resistivity contrast compared to the surrounding unfrozen medium. This study aims to reveal the effects of ongoing climate warming on mountain permafrost by repeating historical ERT and analyzing the temporal changes in the resistivity distribution. In order to facilitate the measurements, we introduce and discuss the employment of textile electrodes. These newly developed electrodes significantly reduce working effort, are easy to deploy on blocky surfaces and yield sufficiently low contact resistances. We analyze permafrost evolution on three periglacial landforms (two rock glaciers and one talus slope) in the Swiss and Austrian Alps by repeating historical surveys after 10, 12 and 16 years, respectively. The resistivity values have been significantly reduced in ice-poor permafrost landforms at all study sites. Interestingly, resistivity values related to ice-rich permafrost in the studied active rock glacier partly increased during the studied time period. To explain this apparently counterintuitive (in view of increased resistivity) observation, geomorphological circumstances, such as the relief and increased creep velocity of the active rock glacier, are discussed by using additional remote sensing data. The present study highlights ice-poor permafrost degradation in the Alps resulting from ever-accelerating global warming

Postglacial denudation of western Tibetan Plateau margin outpaced by long-term exhumation

The Indus River, one of Asia’s premier rivers, drains the western Tibetan Plateau and the Nanga Parbat syntaxis. These two areas juxtapose some of the lowest and highest topographic relief and commensurate denudation rates in the Himalaya-Tibet orogen, respectively, yet the spatial pattern of denudation rates upstream of the syntaxis remains largely unclear, as does the way in which major rivers drive headward incision into the Tibetan Plateau. We report a new inventory of ^(10)Be-based basinwide denudation rates from 33 tributaries flanking the Indus River along a 320 km reach across the western Tibetan Plateau margin. We find that denudation rates of up to 110 mm k.y.^(–1) in the Ladakh and Zanskar Ranges systematically decrease eastward to 10 mm k.y.^(–1) toward the Tibetan Plateau. Independent results from bulk petrographic and heavy mineral analyses support this denudation gradient. Assuming that incision along the Indus exerts the base-level control on tributary denudation rates, our data show a systematic eastward decrease of landscape downwearing, reaching its minimum on the Tibetan Plateau. In contrast, denudation rates increase rapidly 150–200 km downstream of a distinct knickpoint that marks the Tibetan Plateau margin in the Indus River longitudinal profile. We infer that any vigorous headward incision and any accompanying erosional waves into the interior of the plateau mostly concerned reaches well below this plateau margin. Moreover, reported long-term (>10^6 yr) exhumation rates from low-temperature chronometry of 0.1–0.75 mm yr^(–1) consistently exceed our ^(10)Be-derived denudation rates. With averaging time scales of 10^3–10^4 yr for our denudation data, we report postglacial rates of downwearing in a tectonically idle landscape. To counterbalance this apparent mismatch, denudation rates must have been higher in the Quaternary during glacial-interglacial intervals