647 research outputs found
Non-stationary responses of tree-ring chronologies and glacier mass balance to climate in the European Alps
No full textTree-ring width and glacier mass balance are two highly sensitive climatic proxies which are often used as indicators of biological and geophysical changes in high- altitude ecosystems. Tree-ring data have been widely used to reconstruct past temperatures and also to reconstruct past glacier mass balance. Here we show that tree-ring chronologies from a high-altitude Pinus cembra L. dendroclimatic network and glaciers from the same region in the European Alps have non-stationary responses to air temperature, and have also been responding non-proportionally to temperature extremes in recent decades. Both ring-width chronologies and the mass-balance series of some glaciers from the same region have shown an increasing sensitivity to summer (JJA) temperatures. Our results demonstrate that the sensitivity to climate of tree-ring chronologies and glacier mass balance may change over time and has been increasing in recent decades, posing some limitations to tree-ring-based glacier mass-balance reconstruction. Moreover, we found these reconstructions in the European Alps are more reliable for large rather than for small glaciers, and may not be able to reveal years of extreme ablation that could have occurred in the past
Permafrost mapping on glaciers in the Ötztal, Austria
No full textThe occurrence of permafrost in the region of the Hochebenkar rock glaciers has been mapped in detail. For this purpose basal temperatures of the winter snow cover were measured at over 250 sites (BTS-method), II refraction-seismic profiles were taken in frozen and unfrozen unconsolidated sediments and 12 springs were investigated in terms of their summer temperature 128 W. Haeberli und G. PatzeIt variations. The combination of seismic refraction and the BTS-method allows rapid and reliable mapping of alpine permafrost, and at the same time enables differences in active-Iayer thickness to be established. The resuIts of the observations confirm the ideas developed in the Swiss Alps in recent years about the relationships between permafrost and rock glaciers: rock glaciers are creep phenomena of discontinuous alpine permafrost
Potential climatic transitions with profound impact on Europe
No full textWe discuss potential transitions of six climatic subsystems with large-scale impact on Europe, sometimes denoted as tipping elements. These are the ice sheets on Greenland and West Antarctica, the Atlantic thermohaline circulation, Arctic sea ice, Alpine glaciers and northern hemisphere stratospheric ozone. Each system is represented by co-authors actively publishing in the corresponding field. For each subsystem we summarize the mechanism of a potential transition in a warmer climate along with its impact on Europe and assess the likelihood for such a transition based on published scientific literature. As a summary, the ‘tipping’ potential for each system is provided as a function of global mean temperature increase which required some subjective interpretation of scientific facts by the authors and should be considered as a snapshot of our current understanding. <br/
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
No full textNeue 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
Accumulation Characteristics on a Cold, High-Alpine Firn Saddle from a Snow-Pit Study on Colle Gnifetti, Monte Rosa, Swiss Alps
No full textAbstractIn a snow pit, incorporating about 2.5 a of accumulation, on the 4 450 m high Colle Gnifetti, Monte Rosa, various snow characteristics, isotopes (δ18O, 3H), electrical conductivity, dust, trace elements, and pollen were investigated. The aim of this study was to develop a key for the stratigraphic interpretation of cores from cold, high-alpine firn areas. It appears that the strong influence of wind results in mixing and re-sedimentation processes in the surface layers. Nevertheless, by interpreting several parameters in a combined way, it is possible to classify a large number of the layers according to their season and sometimes to their place of origin. Apart from the melt layers, which only appear in early summer to summer layers, other prominent features are the (Saharan) dust falls, characterized by dust and conductivity peaks.</jats:p
Ice and snow as land-forming agents
No full textMany contemporary high-latitude and high-altitude regions are covered by ice and snow perennially or at least for substantial parts of the year, and such coverage extended greatly during colder periods of the Quaternary. Consequently, the landscape of such regions typically bears the strong imprint of ice- and snow-related processes operating over Quaternary-to-modern timescales. There has been strong research interest in the nature, rate, and efficacy of cold-region geomorphic processes, though most research has been devoted to glacial and permafrost phenomena, with comparably few studies having quantitatively addressed the role of snow as a land-forming agent. Here we review current research on land-forming processes related to glacial erosion and deposition, permafrost and periglacial processes, and snow-related processes such as nivation, snow creep, and snow avalanching. Our objective is to highlight those questions that drive current research and indicate others that seem sufficiently worthy to further our understanding of geomorphic form and process in the cryosphere. We do so bearing in mind that such knowledge is essential for successfully predicting form and process, and hence avoiding snow- and ice-related hazards. We conclude by outlining a number of recommendations for future research in the field
An active rock glacier in the southernmost permafrost environment of the Alps (Argentera Massif, Italy): four years of surface ground temperature monitoring
No full text
Retreat instability of tidewater glaciers and marine ice sheets
No full textThe terminus dynamics of tidewater glaciers and marine-based ice sheets are strongly affected by the process of calving and water depth at their termini, resulting in an unstable retreat behavior and accelerated mass loss related to submarine overdeepenings. The governing controls and existing approaches related to this dynamic instability are discussed in this chapter in relation to the Columbia Glacier in Alaska and numerical modeling experiments. The related marine ice sheet instability is further explained, together with the stabilizing influence of floating ice tongues and ice shelves on the grounding line behavior. The chapter concludes with wider implications and future challenges of this dynamic instability as a hazard, such as sea-level rise and accelerated discharge of icebergs
- …
