Wilfried Haeberli

Rapid disintegration of Alpine glaciers observed with satellite data

Analyses of multispectral satellite data indicate accelerated glacier decline around the globe since the 1980s. By using digitized glacier outlines inferred from the 1973 inventory and Landsat Thematic Mapper (TM) satellite data from 1985 to 1999, we obtained area changes of about 930 Alpine glaciers. The 18% area reduction as observed for the period 1985 to 1999 (−1.3% a⁻¹) corresponds to a seven times higher loss rate compared to the 1850–1973 decadal mean. Extrapolation of area change rates and cumulative mass balances to all Alpine glaciers yields a corresponding volume loss of about 25 km³ since 1973. Highly individual and non-uniform changes in glacier geometry (disintegration) indicate a massive down-wasting rather than a dynamic response to a changed climate. Our results imply stronger ongoing glacier retreat than assumed so far and a probable further enhancement of glacier disintegration by positive feedbacks.

Permafrost in steep bedrock slopes and its temperature‐related destabilization following climate change

Permafrost in steep bedrock is abundant in many cold-mountain areas, and its degradation can cause slope instability that is unexpected and unprecedented in location, magnitude, frequency, and timing. These phenomena bear consequences for the understanding of landscape evolution, natural hazards, and the safe and sustainable operation of high-mountain infrastructure. Permafrost in steep bedrock is an emerging field of research. Knowledge of rock temperatures, ice content, mechanisms of degradation, and the processes that link warming and destabilization is often fragmental. In this article we provide a review and discussion of existing literature and pinpoint important questions. Ice-filled joints are common in bedrock permafrost and possibly actively widened by ice segregation. Broad evidence of destabilization by warming permafrost exists despite problems of attributing individual events to this phenomenon with certainty. Convex topography such as ridges, spurs, and peaks is often subject to faster and deeper thaw than other areas. Permafrost degradation in steep bedrock can be strongly affected by percolating water in fractures. This degradation by advection is difficult to predict and can lead to quick and deepdevelopment of thaw corridors along fractures in permafrost and potentially destabilize much greater volumes of rock than conduction would. Although most research on steep bedrock permafrost originates from the Alps, it will likely gain importance in other geographic regions with mountain permafrost.

Application of inventory data for estimating characteristics of and regional climate-change effects on mountain glaciers: a pilot study with the European Alps

A parameterization scheme using simple algorithms for unmeasured glaciers is being applied to glacier inventory data to estimate the basic glaciological characteristics of the inventoried ice bodies and simulate potential climate-change effects on mountain glaciers. For past and potential climate scenarios, glacier changes for assumed mass-balance changes are calculated as step functions between steady-state conditions for time intervals that approximately correspond to the characteristic dynamic response time (a few decades) of the glaciers. In order to test the procedure, a pilot study was carried out in the European Alps where detailed glacier inventories had been compiled around the mid-1970s. Total glacier volume in the Alps is estimated at about 130 km3 for the mid-1970s; strongly negative mass balances are likely to have caused a loss of about 10–20% of this total volume during the decade 1980–90. Backward calculation of glacier-length changes using a mean annual mass balance of 0.25m w.e.a−1 since the end of the “Little Ice Age” around 1850 AD gives considerable scatter but satisfactory overall results as compared with long-term observations. The total loss of Alpine surface ice mass since 1850 can be estimated at about half the original value. An acceleration of this development, with annual mass losses of around 1 m a−1 or more as anticipated from IPCC scenario A for the coming century, could eliminate major parts of the presently existing Alpine ice volume within decades.

The new remote sensing derived Swiss glacier inventory: II. First results.

Abstract A new Swiss glacier inventory is to be compiled from satellite data for the year 2000. The study presented here describes two major tasks: an accuracy assessment of different methods for glacier classification with Landsat Thematic Mapper (TM) data and a digital elevation model (DEM); the geographical information system (GIS)-based methods for automatic extraction of individual glaciers from classified satellite data and the computation of three-dimensional glacier parameters (such as minimum, maximum and median elevation or slope and orientation) by fusion with a DEM. First results obtained by these methods are presented in Part II of this paper (Kääb and others, 2002). Thresholding of a ratio image from TM4 and TM5 reveals the best-suited glacier map. The computation of glacier parameters in a GIS environment is efficient and suitable for worldwide application. The methods developed contribute to the U. S. Geological Survey-led Global Land Ice Measurements from Space (GLIMS) project which is currently compiling a global inventory of land ice masses within the framework of global glacier monitoring (Haeberli and others, 2000).

Six decades of glacier mass-balance observations: a review of the worldwide monitoring network

Abstract Glacier mass balance is the direct and undelayed response to atmospheric conditions and hence is among the essential variables required for climate system monitoring. It has been recognized as the largest non-steric contributor to the present rise in sea level. Six decades of annual mass-balance data have been compiled and made easily available by the World Glacier Monitoring Service and its predecessor organizations. In total, there have been 3480 annual mass-balance measurements reported from 228 glaciers around the globe. However, the present dataset is strongly biased towards the Northern Hemisphere and Europe and there are only 30 ‘reference’ glaciers that have uninterrupted series going back to 1976. The available data from the six decades indicate a strong ice loss as early as the 1940s and 1950s followed by a moderate mass loss until the end of the 1970s and a subsequent acceleration that has lasted until now, culminating in a mean overall ice loss of over 20mw.e. for the period 1946–2006. In view of the discrepancy between the relevance of glacier mass-balance data and the shortcomings of the available dataset it is strongly recommended to: (1) continue the long-term measurements; (2) resume interrupted long-term data series; (3) replace vanishing glaciers by early-starting replacement observations; (4) extend the monitoring network to strategically important regions; (5) validate, calibrate and accordingly flag field measurements with geodetic methods; and (6) make systematic use of remote sensing and geo-informatics for assessment of the representativeness of the available data series for their entire mountain range and for the extrapolation to regions without in situ observations; and (7) make all these data and related meta-information available.

Integrated monitoring of mountain glaciers as key indicators of global climate change: the European Alps

Abstract The internationally recommended multi-level strategy for monitoring mountain glaciers is illustrated using the example of the European Alps, where especially dense information has been available through historical times. This strategy combines in situ measurements (mass balance, length change) with remote sensing (inventories) and numerical modelling. It helps to bridge the gap between detailed local process-oriented studies and global coverage. Since the 1980s, mass balances have become increasingly negative, with values close to –1mw.e. a–1 during the first 5 years of the 21st century. The hot, dry summer of 2003 alone caused a record mean loss of 2.45 mw.e., roughly 50% above the previous record loss in 1998, more than three times the average between 1980 and 2000 and an order of magnitude more than characteristic long-term averages since the end of the Little Ice Age and other extended periods of glacier shrinkage during the past 2000 years. It can be estimated that glaciers in the European Alps lost about half their total volume (roughly 0.5% a–1) between 1850 and around 1975, another 25% (or 1%a–1) of the remaining amount between 1975 and 2000, and an additional 10–15% (or 2–3% a–1) in the first 5 years of this century.

Analysing the creep of mountain permafrost using high precision aerial photogrammetry: 25 years of monitoring Gruben rock glacier, Swiss Alps

Aerophotogrammetrical monitoring of Gruben rock glacier over the period 1970 to 1995 results in a unique time series documenting the three-dimensional surface kinematics of creeping mountain permafrost. In places, the area under study is aAected by historical fluctuations of the polythermal Gruben glacier. Changes in elevation and surface velocities were measured over five consecutive five-year periods using an advanced photogrammetric monoplotting technique of multitemporal stereo models. The measurements are based on a regular grid with a mesh width of 25 metres and have an accuracy of a few centimetres per year. Although surface lifting occurred in places and within individual time intervals, surface subsidence predominated at an average rate of a few centimetres per year in the ‘periglacial’ part of the rock glacier and of a few decimetres per year in the ‘glacier-aAected’ part of the rock glacier which still contains some dead glacier ice in permafrost. Fluctuations in horizontal surface velocities seem to correlate with temporal changes in surface elevation. Analysing flow along principal trajectories and interpreting the advance rate of the front leads to an age estimate of the rock glacier of a few millennia. Dynamic eAects of three-dimensional straining within the creeping permafrost as computed from the measured surface velocity field are estimated to potentially contribute to surface heave or subsidence in the same order of magnitude as the observed vertical changes. Temporal variations of surface altitudes at Gruben rock glacier show distinct similarities with mass balance and surface altitude variations determined on nearby glaciers but at a greatly reduced amplitude. This similarity may indicate that the same climatic forcing (summer temperatures?) could possibly have a predominant influence on permafrost aggradation/degradation as well as on glacier mass balance in mountain areas. #1997 John Wiley & Sons, Ltd.

Global Land Ice Measurements from Space (GLIMS): remote sensing and GIS investigations of the Earth's cryosphere

Abstract Concerns over greenhouse‐gas forcing and global temperatures have initiated research into understanding climate forcing and associated Earth‐system responses. A significant component is the Earths cryosphere, as glacier‐related, feedback mechanisms govern atmospheric, hydrospheric and lithospheric response. Predicting the human and natural dimensions of climate‐induced environmental change requires global, regional and local information about ice‐mass distribution, volumes, and fluctuations. The Global Land‐Ice Measurements from Space (GLIMS) project is specifically designed to produce and augment baseline information to facilitate glacier‐change studies. This requires addressing numerous issues, including the generation of topographic information, anisotropic‐reflectance correction of satellite imagery, data fusion and spatial analysis, and GIS‐based modeling. Field and satellite investigations indicate that many small glaciers and glaciers in temperate regions are downwasting and retreating, although detailed mapping and assessment are still required to ascertain regional and global patterns of ice‐mass variations. Such remote sensing/GIS studies, coupled with field investigations, are vital for producing baseline information on glacier changes, and improving our understanding of the complex linkages between atmospheric, lithospheric, and glaciological processes.

Recent and future warm extreme events and high-mountain slope stability

The number of large slope failures in some high-mountain regions such as the European Alps has increased during the past two to three decades. There is concern that recent climate change is driving this increase in slope failures, thus possibly further exacerbating the hazard in the future. Although the effects of a gradual temperature rise on glaciers and permafrost have been extensively studied, the impacts of short-term, unusually warm temperature increases on slope stability in high mountains remain largely unexplored. We describe several large slope failures in rock and ice in recent years in Alaska, New Zealand and the European Alps, and analyse weather patterns in the days and weeks before the failures. Although we did not find one general temperature pattern, all the failures were preceded by unusually warm periods; some happened immediately after temperatures suddenly dropped to freezing. We assessed the frequency of warm extremes in the future by analysing eight regional climate models from the recently completed European Union programme ENSEMBLES for the central Swiss Alps. The models show an increase in the higher frequency of high-temperature events for the period 2001–2050 compared with a 1951–2000 reference period. Warm events lasting 5, 10 and 30 days are projected to increase by about 1.5–4 times by 2050 and in some models by up to 10 times. Warm extremes can trigger large landslides in temperature-sensitive high mountains by enhancing the production of water by melt of snow and ice, and by rapid thaw. Although these processes reduce slope strength, they must be considered within the local geological, glaciological and topographic context of a slope.

Glacier monitoring within the Global Climate Observing System

Abstract The fluctuation of mountain glaciers is recognized as a high-confidence indicator of air-temperature trends and as a valuable element of a strategy for early detection of possible Man-induced climate changes. The Terrestrial Observation Panel for Climate therefore recommended that glacier mass and area be monitored as part of the Global Climate Observing System (GCOS) established in 1992 by the World Meteorological Organization, the Intergovernmental Oceanographic Commission, the United Nations Environment Programme and the International Council of Scientific Unions. A tiered Global Hierarchical Observing Strategy was developed to be used for all GCOS terrestrial variables. According to this system of tiers, the regional to global representativeness in space and time of the records relating to glacier mass and area should be assessed by more numerous observations of glacier length changes as well as by compilation of regional glacier inventories repeated at time intervals of a few decades, the typical dynamic response time of smaller mountain glaciers. During the 1970s, Fritz Müller directed the Permanent Service on the Fluctuations of Glaciers and the Temporary Technical Secretariat for the World Glacier Inventory. These two bodies were combined in 1986 to form the World Glacier Monitoring Service, which is now responsible for internationally coordinated glacier monitoring, working in close collaboration with the World Data Center for Glaciology, Boulder.