Snow accumulation, firn temperature and solar radiation in the area of the Colle Gnifetti core drilling site (Monte Rosa, Swiss Alps): Distribution patterns and interrelationships

Distributional patterns of glaciological parameters at the Colle Gnifetti core drilling site are described and their interrelationships are brietly discussed. Observations within a stake network established in 1980 furnish information about snow accumulation (short term balance), submergence velocity of ice flow (long term balance), ram hardness (melt layer stratigraphy), and firn temperature. In addition, a numerical model was used to estimate local variations of available radiant energy. Melt layer formation is considerably more intensive on the south facing parts of the firn saddle where incoming radiation is high. These melt layers seem to effectively protect some of the fallen snow from wind erosion. As a result, balance ist up to one order of magnitude larger on south facing slopes. Heat applied to the surface is therefore positively correlated with balance, whereas the relation between solar radiation and firn temperature is less clear. Distributional patterns of submergence velocity confirm that the observed spatial variability of surface balance is representative for longer time periods and greatly influences the time scale and the stratigraphy of firn and ice cores from Colle Gnifetti

Schwindendes Eis und neue Seen – die Hochgebirgslandschaft im rasanten Umbau

Bis Ende Jahrhundert dürften die Gletscher in der Schweiz bis auf wenige Reste abgeschmolzen sein. Dafür werden viele neue Seen entstehen. Das erfordert kreative Lösungen: im Hochwasserschutz, in der Energie- und Wasserversorgung und im Tourismus

GIS-based modelling of rock-ice avalanches from Alpine permafrost areas

Changing permafrost conditions caused by present atmospheric warming are expected to affect the stability of steep rock walls in high mountain areas. The possible increase in periglacial slope instabilities and the especially long potential run-out distances in glacial environments require more awareness about the kind of events as well as robust models to foresee areas affected and distances reached. A geographic information system-based flow-routing model is introduced for modelling rock-ice avalanches on a regional scale. The model application to three major historical events in the European Alps shows the basic use for simulating such events for first-order assessments. By designating the path of steepest descent while allowing lateral spreading from the fall track up to 45°, general flow patterns as well as changes in the direction of progression are well reproduced. The run-out distances are determined using empirically based models and suit well the case studies presente

On the morphological characteristics of overdeepenings in high‐mountain glacier beds

Overdeepenings, i.e. closed topographic depressions with adverse slopes in the direction of flow, are characteristic for glacier beds and glacially sculpted landscapes. Quantitative information about their morphological characteristics, however, has so far hardly been available. The present study provides such information by combining the analysis of (a) numerous bed overdeepenings below still existing glaciers of the Swiss Alps and the Himalaya-Karakoram region modelled with a robust shear stress approximation and (b) detailed bathymetries from recently exposed lakes in the Peruvian Andes. The investigated overdeepenings exist where glacier surface slopes are low (< 5°–10°), occur in bedrock or morainic material and are most commonly a fraction of a kilometre squared in surface area, hundreds of metres long, about half the length in width and tens of metres deep. They form under conditions of low to high basal shear stresses, at cirque, confluence, trunk valley and terminus positions. The most striking phenomenon, however, is the high variability of their geometries: Depths, surface areas, lengths and widths of the overdeepenings vary over orders of magnitude and are only weakly – if at all – interrelated. Inclinations of adverse slopes do not differ significantly from those of forward slopes and are in many cases higher than so far assumed theoretical limits for supercooling of ascending water and corresponding closure of sub-glacial channels. Such steep adverse slopes are a robust observation and in support of recently developed new concepts concerning the question about where supercooling of sub-glacial water and closure of ice channels can or must occur. However, the question of when and under what climatic, topographic and ice conditions the overdeepenings had formed remains unanswered. This open question constitutes a key problem concerning the interpretation of observed overdeepenings, the understanding of the involved glacio-hydraulic processes and the possibility of realistic predictive modelling of overdeepening formation

Mass-balance parameters derived from a synthetic network of mass-balance glaciers

Glacier mass-balance parameters such as the equilibrium-line altitude (ELA) play an important role when working with large glacier samples. While the number of observational mass-balance series to derive such parameters is limited, more and more modeled data are becoming available. Here we explore the possibilities of analyzing such ‘synthetic’ mass-balance data with respect to mass-balance parameters. A simplified energy-balance model is driven by bias-corrected regional climate model output to model mass-balance distributions for 94 glaciers in the Swiss Alps over 15 years. The modeling results in realistic interannual variability and mean cumulative mass balance. Subsequently model output is analyzed with respect to 18 topographic and mass-balance parameters and a correlation analysis is performed. Well-known correlations such as for ELA and median elevation are confirmed from the synthetic data. Furthermore, previously unreported parameter relationships are found such as a correlation of the balance rate at the tongue with the accumulation–area ratio (AAR) and of the glacier elevation range with the AAR. Analyzing modeled data complements in situ observations and highlights their importance: the small number of accurate mass-balance observations available for validation is a major challenge for the presented approach

Modeling glacier thickness distribution and bed topography over entire mountain ranges with GlabTop: Application of a fast and robust approach

The combination of glacier outlines with digital elevation models (DEMs) opens new dimensions for research on climate change impacts over entire mountain chains. Of particular interest is the modeling of glacier thickness distribution, where several new approaches were proposed recently. The tool applied herein, GlabTop (Glacier bed Topography) is a fast and robust approach to model thickness distribution and bed topography for large glacier samples using a Geographic Information System (GIS). The method is based on an empirical relation between average basal shear stress and elevation range of individual glaciers, calibrated with geometric information from paleoglaciers, and validated with radio echo soundings on contemporary glaciers. It represents an alternative and independent test possibility for approaches based on mass-conservation and flow. As an example for using GlabTop in entire mountain ranges, we here present the modeled ice thickness distribution and bed topography for all Swiss glaciers along with a geomorphometric analysis of glacier characteristics and the overdeepenings found in the modeled glacier bed. These overdeepenings can be seen as potential sites for future lake formation and are thus highly relevant in connection with hydropower production and natural hazards. The thickest ice of the largest glaciers rests on weakly inclined bedrock at comparably low elevations, resulting in a limited potential for a terminus retreat to higher elevations. The calculated total glacier volume for all Swiss glaciers is 75 ± 22 km3 for 1973 and 65 ± 20 km3 in 1999. Considering an uncertainty range of ±30%, these results are in good agreement with estimates from other approaches

Glacier–permafrost relations in a high-mountain environment: 5 decades of kinematic monitoring at the Gruben site, Swiss Alps

Digitized aerial images were used to monitor the evolution of perennially frozen debris and polythermal glacier ice at the intensely investigated Gruben site in the Swiss Alps over a period of about 50 years. The photogrammetric analysis allowed for a compilation of detailed spatio-temporal information on flow velocities and thickness changes. In addition, high-resolution GNSS (global navigation satellite system) and ground surface temperature measurements were included in the analysis to provide insight into short-term changes. Over time, extremely contrasting developments and landform responses are documented. Viscous flow within the warming and already near-temperate rock glacier permafrost continued at a constant average but seasonally variable speed of typically decimetres per year, with average surface lowering limited to centimetres to a few decimetres per year. This constant flow causes the continued advance of the characteristic convex, lava-stream-like rock glacier with its oversteepened fronts. Thawing rates of ice-rich perennially frozen ground to strong climate forcing are very low (centimetres per year) and the dynamic response strongly delayed (timescale of decades to centuries). The adjacent cold debris-covered glacier tongue remained an essentially concave landform with diffuse margins, predominantly chaotic surface structure, intermediate thickness losses (decimetres per year), and clear signs of down-wasting and decreasing flow velocity. The former contact zone between the cold glacier margin and the upper part of the rock glacier with disappearing remains of buried glacier ice embedded on top of frozen debris exhibits complex phenomena of thermokarst in massive ice and backflow towards the topographic depression produced by the retreating glacier tongue. As is typical for glaciers in the Alps, the largely debris-free glacier part shows a rapid response (timescale of years) to strong climatic forcing with spectacular retreat (>10 m a−1) and mass loss (up to >1 m w.e. specific mass loss per year). The system of periglacial lakes shows a correspondingly dynamic evolution and had to be controlled by engineering work for hazard protection

Neue Seen als Folge des Gletscherschwundes im Hochgebirge : Chancen und Risiken – Formation de nouveaux lacs suite au recul des glaciers en haute montagne : chances et risques

Gletscherschmelze, Gletschersee, Wassernutzung Neue Seen als Folge des Gletscherschwundes im Hochgebirge: Klimaabhängige Bildung und Herausforderungen für eine nachhaltige Nutzung (Projekt NELAK des NFP 61). Weltweit schwinden die Gletscher rasant, auch die Alpen dürften ihre Gletscher in den kommenden Jahrzehnten weitgehend verlieren. In den eisfreien Gebieten bilden sich dabei zahlreiche neue Seen. Das Projekt NELAK behandelt in einem integrativ-multidisziplinären Ansatz Fragen nach dem optimalen Umgang mit diesen neuen Elementen der Landschaft und des Wasserkreislaufs. In engem Kontakt mit Behörden und Wirtschaft werden Grundlagen zu relevanten Aspekten der Naturgefahren, der Wasserkraft, des Tourismus und des Rechts erarbeitet sowie an Fallbeispielen diskutiert. Der vorliegende Bericht enthält eine erste systematische Wissensbasis sowie Empfehlungen für die dringend notwendige Planung: Was kommt auf uns zu, was können wir tun und wie gehen wir am besten vor? Nouveaux lacs suite au recul des glaciers en haute montagne: développement lié au climat et défis pour une utilisation durable (projet NELAK du PNR 61). Les glaciers déclinent à toute vitesse dans le monde entier; les Alpes ne sont pas épargnées et devraient perdre la plupart de leurs glaciers au cours des prochaines décennies, entraînant la formation de nombreux nouveaux lacs. Le projet NELAK vise à optimiser la gestion des nouveaux éléments du paysage et du cycle hydrologique par le biais d’une approche multidisciplinaire et intégrée. Le contact étroit avec les autorités et les milieux économiques a permis d’élaborer les bases des aspects importants concernant les dangers naturels, l‘énergie hydraulique, le tourisme et le droit; ils sont illustrés à partir d‘études de cas. Ce rapport contient une première base de connaissances systématiques ainsi que des recommandations pour la planification des mesures les plus urgentes: ce qui nous attend, ce que nous pouvons faire et comment le réaliser au mieux

Gletscherschwund und neue Seen in den Schweizer Alpen

Mit fortschreitendem Temperaturanstieg undGletscherschwundbilden sich in Hochgebirgen weltweit viele neue Seen. Model/rechnungen zeigen, dass sich die heute noch existierenden Gletscher-Landschaften der Schweizer Alpen bei realistischen Szenarien der Klimaentwicklung in den kommenden Jahrzehnten fur wahl sehr lange Zeit zu Fe/s-Schutt-Seen-Landschaften mit stark erh6hterAbtragsdynamik verwandeln werden. 1m Projekt NELAK (Neue Seen a/s Folge der Entgletscherung in den Alpen) des Nationalen Forschungsprogramms 61 «Nachhaltige Wassemutzung» werden Grundlagen fOr den Umgang mit dieser absehbaren Entwicklung erarbeitet. Von besonderem Interesse sind im Hinblick auf die anstehenden Neukonzessionierungen im Bereich der Wasserkraft dabei Synergiepotenziale von multifunktionalen Projekten fOr Energieproduktion, sedimentruckhaltundHochwasserschutz. Letzterer betrifft vor aI/em die langfristig ansteigende Wahrscheinlichkeit von grosskalibrigen Sturzereignissen in Seen unmittelbar unterhalb von zunehmend eisfrei werdenden Steilflanken mit tendenziel/ abnehmenderStabilitat. Komplexe Rechtsfragen stehen an und eine fruhzeitige Planung ist angezeigt