Digital terrain models of the southern Chilean ice cap Gran Campo Nevado reflecting the terrain situations of the years 1984 and 2000 were compared in order to obtain the volumetric glacier changes that had occurred during this period. The result shows a slightly negative mean glacier change of 3.80 m. The outlet glacier tongues show a massive thinning, whereas the centre of the ice cap is characterized by a moderate thickening. Thus a distinct altitudinal variability of the glacier change is noticed. Hypothetically this could be explained by the combined effects of increased precipitation and increased mean annual air temperature. Both to verify and to quantify this pattern of climatic change, the mean glacier change as well as its hypsometric variation are compared with the results of a degree-day model. The observed volumetric glacier change is traced back to possible climate forcing and can be linked to an underlying climate change that must be comparable with the effects of a precipitation offset of at least 7–8% and a temperature offset of around 0.3 K compared to the steady-state conditions in the period 1984–2000.

The evolution of surface topography of glaciers in the Swiss Alps is well documented with high-resolution aerial photographs repeatedly recorded since the 1960s and further back in time with topographic maps including elevation contour lines first surveyed in the mid-19th century. In order to quantify and interpret glacier changes in the Swiss Alps, time series of volume changes over the last 100–150 years have been collected. The available datasets provide a detailed spatial resolution for the retreat period since the end of the Little Ice Age. The spatial distribution as well as temporal variations of the thickness change were analyzed. A significant ice loss since the end of the 19th century was observed in the ablation area, while the changes in the accumulation area were small. We found moderate negative secular rates until the 1960s, followed by steady to positive rates for about two decades and strong ice loss starting in the 1980s which has lasted until the present. An evaluation of 19 glaciers revealed a total ice volume loss of about 13km3 since the 1870s, of which 8.7 km3 occurred since the 1920s and 3.5 km3 since 1980. Decadal mean net balance rates for the periods 1920–60, 1960–80 and 1980–present are –0.29, –0.03 and –0.53ma–1w.e., respectively.

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.

Stepwise linear regression models were calibrated against the measured mass balance of glaciers in the Austrian Alps for the prediction of specific annual net balance and summer balance from climatological and topographical input data. For estimation of winter mass balance, a simple ratio between the amount of winter precipitation and the measured winter balance was used. A ratio with a mean value of 2.0 and a standard deviation of 0.44 was derived from the sample of measured winter balances. Climate input data were taken from the HISTALP database which offers a homogenized data source that is outstanding in terms of its spatial and temporal coverage. Data from the Austrian glacier inventory were used as topographical input data. From the group of possible predictors summer air temperature, winter precipitation, summer snow precipitation and continentality (as defined from seasonal temperature variation) were selected as climatological driving forces in addition to lowest glacier elevation and area-weighted mean glacier elevation as topographical driving forces. Summer temperature explains 60% of the variance of summer mass balance and 39% of the variance of annual mass balance. Additional factors increase the explained variance by 22% for summer and 31% for annual net balance. The calibrated mass-balance model was used to reconstruct the mass balance of Hintereisferner and Vernagtferner back to 1800. Whereas the model performs well for Hintereisferner, it fails for some sub-periods for Vernagtferner due to the complicated flow dynamics of the glacier.

Measurements of the retreat and advance of glacier termini are simple and straightforward and in many cases give clear indications about climate history. A careful analysis of glacier type and the processes that override the climate forcing of the mass balance are important for the correct interpretation of terminus variations in terms of climate fluctuations. Regular measurements of glacier variations in Iceland were started in 1930. The Iceland Glaciological Society is now responsible for the monitoring programme. The observed front variations of non-surge-type outlet glaciers of various sizes have closely mimicked major variations of the climate in Iceland during the 20th century. Most of the glaciers retreated rapidly during the warm decades from 1930 to 1960, slowing down as the climate cooled during the following decade, and started to advance after 1970. The rate of advance peaked in the 1980s, after which it slowed down as a consequence of rapid warming of the climate that has taken place since the mid-1980s. Mass-balance measurements show alternating positive and negative mass balance of glaciers during the period 1987–95, but the mass balance has been predominantly negative since 1996. Most glaciers in Iceland began to retreat after 1990, and by 2000 all monitored non-surge-type glaciers in Iceland were retreating. A comparison of the front variations of non-surge-type glaciers and mean summer temperature shows that the major shifts in the climate were followed by a change in the rate of advance or retreat at the termini with a delay of only a few years. This delay does not seem to correlate with the size, the mass turnover or other characteristics of the glacier.

Beginning in 1996, aerial photographs were taken for a new Austrian glacier inventory, resulting in digital elevation models (DEMs) and digital orthoimages. An earlier inventory of the Austrian glaciers containing the original aerial photographs and glacier maps and a manual evaluation of various glacier parameters as of 1969 has been re-evaluated at the present state of the art. The two inventories provide the basis for the comparison of glacier reactions over a period of 29 years. In general a reduction of glacier area is observed for almost all Austrian glaciers between 1969 and 1998. The overall reduction in ice-covered area is 17%. The glacier volume change calculated from the DEMs amounts to about 5 km3. This is almost 22% of the ice volume in Austria in 1969, estimated from a volume–area relation. Changes of individual glaciers, however, show a wide variability, depending on their size and physiographic setting.

Glacier monitoring enables us to detect influences of global warming in high mountain regions. To initiate the establishment of a glacier-monitoring network in northern Eurasia, we studied recent glacier variations in Mongolia using topographical maps, aerial photographs and satellite images (Corona and Landsat). Glaciers in Mongolia exist in the Altai mountains which span approximately 1400 km within Russia, China and Mongolia. Four regions were selected to form the study area: Tavan Bogd region, Turgen massif, Kharkhiraa massif and Tsambagarav massif. During the period from the 1940s to 2000 or from 1968 to 2000, the glaciers in these regions lost 10.2%, 19.3%, 28.0% and 28.8% of their area respectively. The glaciers in the Tavan Bogd, Kharkhiraa and Turgen regions were found to have been almost stationary since 1987/88, while those in Tsambagarav massif showed no significant change in area since 1963. Shrinkage of the glaciers occurred between 1945/68 and 1987/88 in the former regions and between 1948 and 1963 in the latter. Mongolian glaciers seem to behave differently from other glaciers which have been experiencing steady shrinkage recently.

Photogrammetric digital elevation models (DEMs) are often used to derive and monitor surfaces in inaccessible areas. They have been used to monitor the spatial and temporal change of glacier surfaces in order to assess glacier response to climate change. However, deriving photogrammetric DEMs of steep mountainous topography where the surface is often obscured by regions of deep shadow and snow is particularly difficult. Assessing the quality of the derived surface can also be problematic, as high-accuracy ground-control points may be limited and poorly distributed throughout the modelled area. We present a method of assessing the quality of a derived surface through a detailed sensitivity analysis of the DEM collection parameters through a multiple input failure warning model (MIFWM). The variance of a DEM cell elevation is taken as an indicator of surface reliability allowing potentially unreliable areas to be excluded from further analysis. This analysis allows the user to place greater confidence in the remaining DEM. An example of this method is presented for a small mountain glacier in Svalbard, and the MIFWM is shown to label as unreliable more DEM cells over the entire DEM area, but fewer over the glacier surface, than other methods of data quality assessment. The MIFWM is shown to be an effective and easily used method for assessing DEM surface quality.

This paper reports changes in supraglacial debris cover and supra-/proglacial lake development associated with recent glacier retreat (1985–2000) in the central Caucasus Mountains, Russia. Satellite imagery (Landsat TM and ETM+) was used to map the surface area and supraglacial debris cover on six neighbouring glaciers in the Adylsu valley through a process of manual digitizing on a false-colour composite of bands 5, 4, 3 (red, green, blue). The distribution and surface area of supraglacial and proglacial lakes was digitized for a larger area, which extended to the whole Landsat scene. We also compare our satellite interpretations to field observations in the Adylsu valley. Supraglacial debris cover ranges from <5% to >25% on individual glaciers, but glacier retreat between 1985 and 2000 resulted in a 3–6% increase in the proportion of each glacier covered by debris. The only exception to this trend was a very small glacier where debris cover did not change significantly and remote mapping proved more difficult. The increase in debris cover is characterized by a progressive up-glacier migration, which we suggest is being driven by focused ablation (and therefore glacier thinning) at the up-glacier limit of the debris cover, resulting in the progressive exposure of englacial debris. Glacier retreat has also been accompanied by an increase in the number of proglacial and supraglacial lakes in our study area, from 16 in 1985 to 24 in 2000, representing a 57% increase in their cumulative surface area. These lakes appear to be impounded by relatively recently lateral and terminal moraines and by debris deposits on the surface of the glacier. The changes in glacier surface characteristics reported here are likely to exert a profound influence on glacier mass balance and their future response to climate change. They may also increase the likelihood of glacier-related hazards (lake outbursts, debris slides), and future monitoring is recommended.

Recent studies have indicated that widespread wastage of glaciers in western China has occurred since the late 1970s. By using digitized glacier outlines derived from the 1970 inventory and Landsat satellite data from 1990/91 to 2001, we obtained area changes of about 278 glaciers with a total area of 2711.57 km2 in the heavily glaciated west Kunlun Shan (WKS) in the northern Tibetan Plateau (TP). Results indicate that the prevailing characteristic of glacier variation is ice wastage, and glacier area decreased by 10 km2 (0.4% of the total 1970 area) between 1970 and 2001. Both the south and north slopes of the WKS presented shrinkage during 1970–2001, but whereas on the north slope a slight enlargement of ice extent during 1970–90 was followed by a reduction of 0.2% during 1990–2001, on the south slope the glacier area decreased by 1.2% during 1970–91, with a small increment of 0.6% during 1991–2001. Comparisons with other glaciated mountainous regions in western China show that glaciers in the research area have experienced less retreat. Based on records from the Guliya ice core, we believe that an increase in air temperature was the main forcing factor for glacier shrinkage during 1970–2001.

This study assesses glacier fluctuations on Disko Island (Qeqertarsuaq), central West Greenland, during the 20th century. A total of 247 glaciers, of which 75 are classified as surge-type glaciers, are included, representing about 95% of the glacierized area. Based on expedition accounts and early maps, it is concluded that recession rates were highest during the first half of the century. Between 1953 and 2005, 70% of the glaciers showed recession, 28% remained stationary and 2% experienced overall advance due to glacier surging. The mean recession rate of quiescent surge-type glaciers was 20 ma–1 compared to 8ma–1 for normal glaciers. Identification of changes in glacier length controlled by climate changes is achieved by excluding surge-type glaciers from the dataset. The result indicates that glaciers with ablation areas facing in the arc south to northwest, covering an area above 5 km2 and having a terminus elevation below 800 m are the most climate-sensitive.

Net changes in glacier area in the region 50–51˚ N, 116–125˚W, which includes the Columbia and Rocky Mountains (1951/52–2001) and the Coast Mountains (1964/65–2002), were determined through a comparison of historic aerial photography and contemporary Landsat 7 ETM+ imagery. The volumes of individual glaciers were estimated using an empirical volume–area scaling relationship. The area of glaciers in the Coast Mountains decreased by 120±10km2, or 5%of the initial ice-covered area here. The areas of glaciers in the Columbia and Rocky Mountains decreased by 20 and 6km2 respectively, corresponding to relative changes in total area of –5% and –15%. The estimated total ice volume loss from the whole region was 13 ±3 km3. In all parts of the study area, the relative changes in area of individual glaciers showed considerable variability, while the smallest glaciers remained essentially unchanged. This suggests that local factors unique to individual glaciers largely determine their sensitivity to climatic change, and that the very small glaciers are collectively less sensitive to such change.

Eliot Glacier is a small (1.6 km2) glacier on Mount Hood, Oregon, USA, and its ablation zone is largely covered with rock debris. We examine the interrelated processes of ablation rates, ice thickness and surface velocities to understand the retreat rate of this glacier. Since measurements began in 1901, the glacier has retreated 680 m, lost 19% of its area and thinned by about 50 m at the lower glacier profile before the terminus retreated past that point. The upper profile, 800m up-glacier, has shown thinning and thickening due to a kinematic wave resulting from a cool period during the 1940s–70s, and is currently about the same thickness as in 1940. Overall, the glacier has retreated at a slower rate than other glaciers on Mount Hood. We hypothesize that the rock debris covering the ablation zone reduces Eliot Glacier’s sensitivity to global warming and slows its retreat rate compared to other glaciers on Mount Hood. Spatial variations in debris thickness are the primary factor in controlling spatial variations in melt. A continuity model of debris thickness shows the rate of debris thickening down-glacier is roughly constant and is a result of the compensating effects of strain thickening and debris melt-out from the ice.

Eddy covariance data collected over a horizontal surface on the largest ice body on Kilimanjaro, Tanzania, over 26–29 July 2005 were used to assess the uncertainty of calculating sublimation with a surface energy balance (SEB) model. Data required for input to the SEB model were obtained from an existing automatic weather station. Surface temperatures that were solved iteratively by the SEB model were used to compute emitted longwave radiation, turbulent heat fluxes using the aerodynamic bulk method and the subsurface heat flux. Roughness lengths for momentum and temperature, which were found to be the most important input parameters controlling the magnitude of modelled (bulk method) turbulent heat fluxes, were obtained using eddy covariance data. The roughness length for momentum was estimated to be 1.7×10–3 m, while the length for temperature was one order of magnitude smaller. Modelled sensible and latent heat fluxes (bulk method) compared well to eddy covariance data, with root-mean-square differences between 3.1 and 4.8 Wm–2 for both turbulent heat fluxes. Modelled sublimation accounted for about 90% of observed ablation, confirming that mass loss by melting is much less important than sublimation on the horizontal surfaces of the remaining plateau glaciers on Kilimanjaro.

Volume–area scaling provides a practical alternative to ice-flow modelling to account for glacier size changes when modelling the future evolution of glaciers; however, uncertainties remain as to the validity of this approach under non-steady conditions. We address these uncertainties by deriving scaling exponents in the volume–area relationship from one-dimensional ice-flow modelling. We generate a set of 37 synthetic steady-state glaciers of different sizes, and then model their volume evolution due to climate warming and cooling as prescribed by negative and positive mass-balance perturbations, respectively, on a century timescale. The scaling exponent derived for the steady-state glaciers (γ = 1.56) differs from the exponents derived for the glaciers in transient (non-steady) state by up to 86%. Nevertheless, volume projections employing volume–area scaling are relatively insensitive to these differences in scaling exponents. Volume–area scaling agrees well with the results from ice-flow modelling. In addition, the scaling method is able to simulate the approach of a glacier to a new steady state, if mass-balance elevation feedback is approximated by removing or adding elevation bands at the lowest part of the glacier as the glacier retreats or advances. If area changes are approximated in the mass-balance computations in this way, our results indicate that volume–area scaling is a powerful tool for glacier volume projections on multi-century timescales.

Austfonna (8120km2) is by far the largest ice mass in the Svalbard archipelago. There is considerable uncertainty about its current state of balance and its possible response to climate change. Over the 2004/05 period, we collected continuous meteorological data series from the ice cap, performed mass-balance measurements using a network of stakes distributed across the ice cap and mapped the distribution of snow accumulation using ground-penetrating radar along several profile lines. These data are used to drive and test a model of the surface mass balance. The spatial accumulation pattern was derived from the snow depth profiles using regression techniques, and ablation was calculated using a temperature-index approach. Model parameters were calibrated using the available field data. Parameter calibration was complicated by the fact that different parameter combinations yield equally acceptable matches to the stake data while the resulting calculated net mass balance differs considerably. Testing model results against multiple criteria is an efficient method to cope with non-uniqueness. In doing so, a range of different data and observations was compared to several different aspects of the model results. We find a systematic underestimation of net balance for parameter combinations that predict observed ice ablation, which suggests that refreezing processes play an important role. To represent these effects in the model, a simple PMAX approach was included in its formulation. Used as a diagnostic tool, the model suggests that the surface mass balance for the period 29 April 2004 to 23 April 2005 was negative (–318mmw.e.).

Interferometric synthetic aperture radar data show that Devon Ice Cap (DIC), northern Canada, is drained through a network of 11 glacier systems. More than half of all ice discharge is through broad flows that converge to the southeast of the ice cap, and these are grounded well below sea level at their termini. A calculation of the ice-cap mass budget reveals that the northwestern sector of DIC is gaining mass and that all other sectors are losing mass. We estimate that a 12 489 km2 section of the main ice cap receives 3.46±0.65 Gt of snowfall each year, and loses 3.11±0.21 Gt of water through runoff, and 1.43±0.03 Gt of ice through glacier discharge. Altogether, the net mass balance of DIC is –1.08±0.67 Gt a–1. This loss corresponds to a 0.003 mma–1 contribution to global sea levels, and is about half the magnitude of earlier estimates.

A model using upper-air meteorological variables in the US National Centers for Environmental Prediction and US National Center for Atmospheric Research (NCEP/NCAR) re-analysis database is used to extend net balance bn back to 1948 for seven glaciers in southern Norway. The observational record of another glacier, Storbreen, began in 1948. Over the observational record of each of the seven glaciers, correlation with Storbreen estimates bn more accurately than the upper-air model does for four of them and less accurately for three. In all seven cases, however, an average of the model and the Storbreen correlation is more accurate than either alone, so the average is used to reconstruct bn for years when it was not observed. For the seven glaciers other than Storbreen, a combined series is formed from observations during their period of record and from reconstructed values prior to then back to 1948. There are three distinct sections in all eight bn series: prior to 1989; 1989–1995, when the North Atlantic Oscillation index was strongly positive; and after 1995. The 1989–95 mean bn was anomalously positive because of both decreased ablation and especially increased accumulation. The mean bn since 1995 has been anomalously negative because of increased ablation, whilst accumulation has been nearly the same as over 1948–88. The first principal component of the eight 1949–2005 bn series explains 78% of the total variance, and the second explains 12%. Over 1949–88 there were no substantial shifts in bn or in either winter balance bw or summer balance bs at any of the seven glaciers where observations began after 1948, nor were there in the Storbreen record. There is a distinction between the three glaciers that gained mass over 1948–2005 and the five that lost mass. Each of the three that gained had accumulation-area ratio AAR ≥ 0.64 and <0.7% of its area δS in the lowest tenth of its altitude range, while the five that lost had AAR ≤ 0.46 and 1.9 ≤ δS ≤ 4.4%. Because of these hypsometries, the five glaciers that lost mass now have an especially large ablation area.

Regional summer temperatures (TS), derived from tree rings, and large-scale atmospheric circulation indices (North Atlantic Oscillation (NAO)) were used to infer the mass balance of Storglaciären, Sweden, on annual and decadal timescales back to AD 1500. Winter (January–March) NAO was not a suitable proxy for interannual winter balance variability, but seemed to have substantial influence on decadal timescales. TS were highly correlated to the summer balance, but also to the annual net balance. This association was much weaker on decadal timescales, mainly because of the increased maritime climate around 1980. Storglaciären net balance was modelled back to AD 1500 with annual resolution (using TS as a predictor), and AD 1664 with decadal resolution (using TS and NAO as predictors). Both reconstructions displayed similar evolution. Negative mass balances dominated most of the 16th century, followed by a longer period of predominantly positive mass-balance years culminating in about 1750. This is in agreement with previous suggestions of Holocene maximum expansion of Storglaciären at that time. Subsequently, the mass balance is highly variable, with an increased number of negative years. The build-up to the well-documented early-20th-century advance is evident as mass balance becomes progressively more positive towards the early 20th century.

To study the past and future evolution of Rhonegletscher, Switzerland, a flowline model was developed to include valley shape effects more accurately than conventional flowband models. In the model, the ice flux at a gridpoint was computed by a two-dimensional ice-flow model applied to the valley cross-section. The results suggested the underestimation of the accumulation area, which seems to be a general problem of flowline modelling arising from the model’s one-dimensional nature. The corrected mass balance was coupled with the equilibrium-line altitude (ELA) change, which was reconstructed for the period 1878–2003 from temperature and precipitation records, to run the model for the past 125 years. The model satisfactorily reproduced both changes in the terminus position and the total ice volume derived from digital elevation models of the surface obtained by analyses of old maps and aerial photographs. This showed the model’s potential to simulate glacier evolution when an accurate mass balance could be determined. The future evolution of Rhonegletscher was evaluated with three mass-balance conditions: the mean for the period 1994–2003, and the most negative (2003) and positive (1978) mass-balance values for the past 50 years. The model predicted volume changes of –18%, –58% and +38% after 50 years for the three conditions, respectively.