Glacier Length Research Articles

Glacier change in Norway since the 1960s – an overview of mass balance, area, length and surface elevation changes

AbstractIn this paper, we give an overview of changes in area, length, surface elevation and mass balance of glaciers in mainland Norway since the 1960s. Frontal advances have been recorded in all regions except the northernmost glaciers in Troms and Finnmark (Storsteinsfjellbreen, Lyngen and Langfjordjøkelen). More than half of the observed glaciers, 27 of 49, had marked advances in the 1990s. The glaciological mass-balance values for the period 1962–2018, where 43 glaciers have been measured, show great inter-annual variability. The results reveal accelerated deficit since 2000, the most negative decade being 2001–2010. Some years with a positive mass balance (or less negative) after 2010s can be attributed to variations in large-scale atmospheric circulation. A surface elevation change and geodetic mass balance were calculated for a sample of 131 glaciers covering 817 km2 in the ‘1960s’ and 734 km2 in the ‘2010s’, giving an area reduction of 84 km2, or 10%. The sample covers many of the largest glaciers in Norway, and they had an overall change in surface elevation of −15.5 m for the ~50 year period. Converted to a geodetic mass balance this gives a mean mass balance of −0.27 ± 0.05 m w.e. a−1.

Initialization of a global glacier model based on present-day glacier geometry and past climate information: an ensemble approach

Abstract. To provide estimates of past glacier mass changes over the course of the 20th century, an adequate initial state is required. However, empirical evidence about past glacier states at regional or global scales is largely incomplete, both spatially and temporally, calling for the use of automated numerical methods. This study presents a new way to initialize the Open Global Glacier Model from past climate information and present-day glacier states. We use synthetic experiments to show that even with these perfectly known but incomplete boundary conditions, the problem of model initialization is an ill-posed inverse problem leading to nonunique solutions, and we propose an ensemble approach as a way forward. The method works as follows: we generate a large set of physically plausible glacier candidates for a given year in the past (e.g., 1850 in the Alps), all of which are then modeled forward to the date of the observed glacier outline and evaluated by comparing the results of the forward runs to the present-day states. We test the approach on 2660 Alpine glaciers and determine error estimates of the method from the synthetic experiments. The results show that the solution is often nonunique, as many of the reconstructed initial states converge towards the observed state in the year of observation. We find that the median state of the best 5 % of all acceptable states is a reasonable best estimate. The accuracy of the method depends on the type of the considered observation for the evaluation (glacier length, area, or geometry). Trying to find past states from only present-day length instead of the full geometry leads to a sharp increase in uncertainty. Our study thus also provides quantitative information on how well the reconstructed initial glacier states are constrained through the limited information available to us. We analyze which glacier characteristics influence the reconstructability of a glacier, and we discuss ways to develop the method further for real-world applications.

Simulation of the dynamics of the Hansbreen tidal glacier (Svalbard) based on the stochastic model

The dynamics of the Hansbreen tidal glacier (Svalbard) is manifested at different time scales. In addition to the long-term trend, there are noticeable inter-annual fluctuations. And the last ones are precisely the subject of this work. Based on general conclusions of the theory of temporal dynamics of the massive inertial objects, the observed inter-annual changes in the length of the glacier can be explained as a result of the accumulation of anomalies of the heat fluxes and water flows. In spite the fact that the initial model of glacier dynamics is deterministically based on the physical law of conservation of ice mass (the so-called the «minimal model» was used), the model of length change is interpreted as stochastic. From this standpoint, it is the Langevin equation, which includes the effect of random temperature anomalies that can be interpreted as a white noise. From a mathematical point of view, this process is analogous to Brownian motion, i.e. the length of the Hansbreen glacier randomly fluctuates in the vicinity of its stable equilibrium position. Based on the Langevin equation, we passed to the Fokker–Planck equation, the solution of which allowed us to obtain the distribution function of the probabilities of interannual fluctuations of glacier length, which is close to the normal law. It was shown that the possible range of the variability covers the observed interval of the length fluctuations. The pdf is close to normal distribution.

Evolution of the largest glacier in Mexico (Glaciar Norte) since the 50s: factors driving glacier retreat

ABSTRACTThe evolution of Mexican glaciers (19° N) in the climate context is poorly understood despite these glaciers are important indicators of regional climate change. The detailed patterns of glacier recession since the Little Ice Age (LIA) have exacerbated during the past years and decades. Their relationship to local and regional climate change needs further analysis. This study compares the changes of the largest glacier in Mexico, Glaciar Norte (GN), on Citlaltépetl Volcano with temperature, precipitation, and surface energy balance variations that were considered as part of climate forcing. Area, length, elevation, equilibrium line altitude (ELA), and thickness were calculated from historical and satellite data sets and a high-resolution Digital Elevation Model. The results showed that during the 1990s, prevailing warm and variable dry conditions enhanced the glacier retreat, triggering the disappearance of Jamapa glacier tongue. The glacier length has changed at the rate of −20.7 m a−1 since 1958. ELA varied from 4999 m a.s.l. in 1958–5228 m a.s.l. in 2017. A short period of snow accumulation from 2007 to 2009 was found when the annual temperature over GN showed a noticeable negative trend similar to that for the accumulated surface energy balance. The surface energy balance was conclusive on the response of GN to stability or accumulation periods. Finally, the long-term variation of temperature was the only factor found forcing the glacier retreat. Assuming that the retreat rate (−0.02 km a−1) and climate tendencies remained constant (0.1°C/decade), GN could disappear towards the middle of the twenty-first century.

A dataset of glacier length in Chinese Altay Mountains from 1959 to 2016

A dataset of glacier length in Chinese Altay Mountains from 1959 to 2016

Interannual climate variability helps define the mean state of glaciers

ABSTRACTChanges in glacier length and extent are indicators of contemporary and archives of past climate changes, but this common climate proxy presents a challenge for inferring a climate signal. Modeling studies suggest that length fluctuations can occur due to interannual climate variability within an unchanging mean climate and that changes in interannual climate variability can also drive changes in average length. This paper quantifies the impacts of interannual climate variability on average glacier length and mass balance, using a flowline model coupled to a simplified mass-balance model. Results illustrate that changes in the magnitude of interannual temperature variability can non-linearly affect the mean glacier length through a mass-balance asymmetry between warm and cold years. This asymmetry is present in models where melt only initiates after a temperature threshold is crossed. Glaciers susceptible to this asymmetry can be identified based on the shape of their mass-balance profiles. The presence of mass-balance asymmetries in glaciological databases is evaluated, but current records are too short for high statistical resolving power. While the asymmetry in this study can affect the average length and mass-balance, its impacts are small, and paleoclimate interpretations from glacier-length changes are likely not notably influenced by this process.

Long-term records of glacier surface velocities in the Ötztal Alps (Austria)

Abstract. Climatic forcing affects glacier mass balance, which causes changes in ice flow dynamics and glacier length changes on different timescales. Mass balance and length changes are operationally used for glacier monitoring, whereas only a few time series of glacier dynamics have been recorded. Here we present a unique dataset of yearly averaged ice flow velocity measurements at stakes and stone lines covering more than 100 years on Hintereisferner and more than 50 years on Kesselwandferner. Moreover, the dataset contains sub-seasonal variations in ice flow from Gepatschferner and Taschachferner covering almost 10 years. The ice flow velocities on Hintereisferner and (especially) on Kesselwandferner show great variation between advancing and retreating periods, with magnitudes increasing from the stakes at higher elevations to the lower-elevated stakes, making ice flow records at ablation stakes a very sensitive indicator of glacier state. Since the end of the latest glacier advances from the 1970s to the 1980s, the ice flow velocities have decreased continuously, a strong indicator of the negative mass balances of the glaciers in recent decades. The velocity datasets of the four glaciers are available at https://doi.org/10.1594/PANGAEA.896741.

Glacier Change in the Yigong Zangbo Basin, Tibetan Plateau, China

Distinguishing debris-covered glaciers from debris-free glaciers is difficult when using only optical remote sensing images to extract glacier boundaries. According to the features that the surface temperature of debriscovered glacier is lower than surrounding objects, and higher than clean glaciers, glacial changes in the Yigong Zangbo basin was analyzed on the basis of visible, near-infrared and thermal-infrared band images of Landsat TM and OLI/TIRS in the support of ancillary digital elevation model (DEM). The results indicated that glacier area gradually declined from 928.76 km2 in 1990 to 918.46 km2 in 2000 and 901.51 km2 in 2015. However, debriscovered glacier area showed a slight increase from 63.39 km2 in 1990 to 66.24 km2 in 2000 and 71.16 km2 in 2015. During 25 years, the glacier length became shorter continuously with terminus elevation rising up. The area of moraine lakes in 1990 was 1.43 km2, which increased to 1.98 km2 in 2000 and 3.41 km2 in 2015. In other words, the total area of the moraine lakes in 2015 is 2.38 times of that in 1990. This increase in moraine lake area could be the result of accelerated glacier melt and retreat, which is consistent with the significant warming trend in recent decades in the basin.

Three-Dimensional Glacier Changes in Geladandong Peak Region in the Central Tibetan Plateau

In this study, contour lines from the topographic maps at a 1:100,000 scale (mapped in 1968), Landsat MSS/TM/OLI images, ASTER images and SPOT 6-7 stereo image pairs were used to study changes in glacier length, area and surface elevation. We summarized the results using the following three conclusions: (1) During the period from 1973 to 2013, glaciers retreated by 412 ± 32 m at a mean retraction rate of 10.3 ± 0.8 m·year−1 and the relative retreat was 5.6 ± 0.4%. The glacier area shrank by 7.5 ± 3.4%, which was larger than the glacier length. In the periods of 1968–2000, 2000–2005 and 2000–2013, the glacier surface elevation change rates were −7.7 ± 1.4 m (−0.24 ± 0.04 m·year−1), −1.9 ± 1.5 m (−0.38 ± 0.25 m·year−1) and −5.0 ± 1.4 m (−0.38 ± 0.11 m·year−1), respectively. The changes in the glacier area and thickness exhibited similar trends, both showing a significant increasing reduction after 2000. (2) Eleven glaciers were identified as surging glaciers. Changes of the mass balance in surging glaciers were stronger than in non-surging glaciers between 1968 and 2013. Changes of area in surging glaciers were weaker than in non-surging glaciers. (3) Increasing temperature was the major cause of glacier thickness reduction and area shrinkage. The increase in precipitation, to a certain extent, inhibited glacial ablation but it did not change the status of the shrinkage in the glacial area and the reduction in the glacier thickness.

Modelling the late Holocene and future evolution of Monacobreen, northern Spitsbergen

Abstract. Monacobreen is a 40 km long surge-type tidewater glacier in northern Spitsbergen. During 1991–1997 Monacobreen surged and advanced by about 2 km, but the front did not reach the maximum Little Ice Age (LIA) stand. Since 1997 the glacier front is retreating at a fast rate (∼125 m a−1). The questions addressed in this study are as follows: (1) Can the late Holocene behaviour of Monacobreen be understood in terms of climatic forcing?, and (2) What will be the likely evolution of this glacier for different scenarios of future climate change? Monacobreen is modelled with a minimal glacier model, including a parameterization of the calving process as well as the effect of surges. The model is driven by an equilibrium-line altitude (ELA) history derived from lake sediments of a nearby glacier catchment in combination with meteorological data from 1899 onwards. The simulated glacier length is in good agreement with the observations: the maximum LIA stand, the front position at the end of the surge, and the 2.5 km retreat after the surge (1997–2016) are well reproduced (the mean difference between observed and simulated glacier length being 6 % when scaled with the total retreat during 1900–2016). The effect of surging is limited. Directly after a surge the initiated mass balance perturbation due to a lower mean surface elevation is about -0.13mw.e.a-1, which only has a small effect on the long-term evolution of the glacier. The simulation suggests that the major growth of Monacobreen after the Holocene climatic optimum started around 1500 BCE. Monacobreen became a tidewater glacier around 500 BCE and reached a size comparable to the present state around 500 CE. For the mid-B2 scenario (IPCC, 2013), which corresponds to a ∼2ma-1 rise of the ELA, the model predicts a volume loss of 20 % to 30 % by the year 2100 (relative to the 2017 volume). For a ∼4ma-1 rise in the ELA this is 30 % to 40 %. However, much of the response to 21st century warming will still come after 2100.

Testing the consistency between changes in simulated climate and Alpine glacier length over the past millennium

Abstract. It is standard to compare climate model results covering the past millennium and reconstructions based on various archives in order to test the ability of models to reproduce the observed climate variability. Up to now, glacier length fluctuations have not been used systematically in this framework even though they offer information on multi-decadal to centennial variations complementary to other records. One reason is that glacier length depends on several complex factors and so cannot be directly linked to the simulated climate. However, climate model skill can be measured by comparing the glacier length computed by a glacier model driven by simulated temperature and precipitation to observed glacier length variations. This is done here using the version 1.0 of the Open Global Glacier Model (OGGM) forced by fields derived from a range of simulations performed with global climate models over the past millennium. The glacier model is applied to a set of Alpine glaciers for which observations cover at least the 20th century. The observed glacier length fluctuations are generally well within the range of the simulations driven by the various climate model results, showing a general consistency with this ensemble of simulations. Sensitivity experiments indicate that the results are much more sensitive to the simulated climate than to OGGM parameters. This confirms that the simulations of glacier length can be used to evaluate the climate model performance, in particular the simulated summer temperatures that largely control the glacier changes in our region of interest. Simulated glacier length is strongly influenced by the internal variability in the system, putting limitations on the model–data comparison for some variables like the trends over the 20th century in the Alps. Nevertheless, comparison of glacier length fluctuations on longer timescales, for instance between the 18th century and the late 20th century, appear less influenced by the natural variability and indicate clear differences in the behaviour of the various climate models.

Committed retreat: controls on glacier disequilibrium in a warming climate

ABSTRACTThe widespread retreat of mountain glaciers is a striking emblem of recent climate change. Yet mass-balance observations indicate that many glaciers are out of equilibrium with current climate, meaning that observed retreats do not show the full response to warming. This is a fundamental consequence of glacier dynamics: mountain glaciers typically have multidecadal response timescales, and so their response lags centennial-scale climate trends. A substantial difference between transient and equilibrium glacier length persists throughout the warming period; we refer to this length difference as ‘disequilibrium’. Forcing idealized glacier geometries with gradual warming shows that the glacier response timescale fundamentally governs the evolution of disequilibrium. Comparing a hierarchy of different glacier models suggests that accurate estimates of ice thickness and climatology, which control the timescale, are more important than higher order ice dynamics for capturing disequilibrium. Current glacier disequilibrium has previously been estimated for a selection of individual glaciers; our idealized modeling shows that sustained disequilibrium is a fundamental response of glacier dynamics, and is robust across a range of glacier geometries. This implies that many mountain glaciers are committed to additional, kilometer-scale retreats, even without further warming. Disequilibrium must also be addressed when calibrating glacier models used for climate reconstructions and projections of retreat in response to future warming.

Combined use of volume-area and volume-length scaling relationships in glacio-hydrological simulation

Abstract Glacier changes are driven by glacier melt, which in turn affects streamflow. This paper describes an accounting scheme for glacier area change distribution across elevation profiles for application in the glacier module of the Soil and Water Assessment Tool (SWAT) model. In addition to volume-area scaling relationship in the module, the paper introduced volume-length scaling relations to estimate changing glacier terminus and update glacier area changes between equilibrium line altitude (ELA) and the terminus. The improved scheme was used in the nested Urumqi Glacier No. 1 catchment and Urumqi River Basin in Tienshan Mountains, China. Comparison of the simulated and observed data suggested that the new scheme accurately reproduced the length and area changes of Glacier No. 1. The contributions of glacier melt and ice melt to runoff were estimated at 71% and 38% for Glacier No. 1 Hydrological Station and 11.1% and 5.8% for Yingxiongqiao Hydrological Station, respectively. This helped to better interpret long-term monitored glacio-hydrological processes of Glacier No. 1 and the variation of glacier melt contribution to streamflow at the catchment scale.

Rapid age assessment of glacial landforms in the Pyrenees using Schmidt hammer exposure dating (SHED)

AbstractSchmidt hammer (SH) sampling of 54 10Be-dated granite surfaces from the Pyrenees reveals a clear relationship between exposure and weathering through time (n=52, R2=0.96, P<0.01) and permits the use of the SH as a numerical dating tool. To test this 10Be-SH calibration curve, 100 surfaces were sampled from five ice-front positions in the Têt catchment, eastern Pyrenees, with results verified against independent 10Be and 14C ages. Gaussian modelling differentiates Holocene (9.4±0.6 ka), Younger Dryas (12.6±0.9 ka), Oldest Dryas (16.1±0.5 ka), last glacial maximum (LGM; 24.8±0.9 ka) and Würmian maximum ice extent stages (MIE; 40.9±1.1 ka). These data confirm comparable glacier lengths during the LGM and MIE (~300 m difference), in contrast to evidence from the western Pyrenees (≥15 km), reflecting the relative influence of Atlantic and Mediterranean climates. Moreover, Pyrenean glaciers advanced significantly during the LGM, with a local maximum at ~25 ka, driven by growth of the Laurentide Ice Sheet, southward advection of the polar front, and a solar radiation minimum in the Northern Hemisphere. This calibration curve is available online (http://shed.earth) to enable wider application of this method throughout the Pyrenees.

Glacier change in the Gangdise Mountains, southern Tibet, since the Little Ice Age

Delineating glacier change during the Little Ice Age (LIA) is of great importance when attempting to understand regional climatic changes and can also help to improve the understanding of any predictions of future glacial changes. However, such knowledge is still lacking for some critical regions of the Tibetan Plateau (TP). In this study, we mapped 4188 contemporary glaciers and reconstructed 1216 LIA areas of glacial coverage in the Gangdise Mountains to the north of the Himalaya using Google Earth satellite imagery. We estimated their paleoglacial areas and equilibrium line altitudes (ELAs) based on the toe-to-headwall altitude ratio (THAR) method. Results show that most glaciers are small (<1 km2), with slope/hanging glaciers the most common (2844 out of 4188 glaciers), while valley glaciers have the greatest coverage (1009.0 km2 out of a total area of 1723.7 km2). Contemporary glaciers have retreated significantly since the LIA, with reductions in length of between 5.5% and 94.7% (mean glacier length 696 m; mean reduction in length 41.7%) and reductions in glacier area of between 4.1% and 94.9% (mean glacier area 0.42 km2; mean reduction in area 44.8%). These reductions have occurred under different local climatic and topographic conditions. The contemporary ELA ranges from 5516 to 6337 m asl; the LIA ELA ranged from 5476 to 6329 m asl. Contemporary and LIA ELA values rise from southeast to northwest. As a general rule, the rise in the ELA value decreases from the eastern to the central Gangdise Mountains and then increases westward, with a mean ELA rise of 45 m. Multiple regression models suggest that 46.8% of the glacier area loss can be explained by glacier elevation, area, and slope. However, only 15.5% of the rise in ELA values can be explained by glacial geometric, topographic, or locational parameters. The spatial pattern of modern ELA values in this region appears inversely related to precipitation, which decreases from southeast to northwest, implying that precipitation is one of the key controls of ELAs. This is also consistent with results from elsewhere in High Asia. In contrast to the Gangdise Mountains' eastern and western sectors, glaciers in the central sector have undergone less change, i.e., in terms of reductions in length, area loss, and rises in ELA. Topography can of course also influence glacial change by creating shielding and/or rainshadow effects and by affecting local temperatures.

Review of the status and mass changes of Himalayan-Karakoram glaciers

ABSTRACTWe present a comprehensive review of the status and changes in glacier length (since the 1850s), area and mass (since the 1960s) along the Himalayan-Karakoram (HK) region and their climate-change context. A quantitative reliability classification of the field-based mass-balance series is developed. Glaciological mass balances agree better with remotely sensed balances when we make an objective, systematic exclusion of likely flawed mass-balance series. The Himalayan mean glaciological mass budget was similar to the global average until 2000, and likely less negative after 2000. Mass wastage in the Himalaya resulted in increasing debris cover, the growth of glacial lakes and possibly decreasing ice velocities. Geodetic measurements indicate nearly balanced mass budgets for Karakoram glaciers since the 1970s, consistent with the unchanged extent of supraglacial debris-cover. Himalayan glaciers seem to be sensitive to precipitation partly through the albedo feedback on the short-wave radiation balance. Melt contributions from HK glaciers should increase until 2050 and then decrease, though a wide range of present-day area and volume estimates propagates large uncertainties in the future runoff. This review reflects an increasing understanding of HK glaciers and highlights the remaining challenges.

Variations of Laohugou Glacier No. 12 in the western Qilian Mountains, China, from 1957 to 2015

Glaciers were solid reservoirs and important water resources in western China, but they were retreating significantly in context of global warming. Laohugou Glacier No. 12 was the largest valley glacier in Qilian Mountains. In this study, real-time kinematic (RTK) data, topographic map and WorldView-2 satellite imagery were used to measure changes in terminus, extent and volume of Laohugou Glacier No. 12. Results showed that Laohugou Glacier No. 12 was shrinking significantly since 1957. From 1960 to 2015, the terminus reduction of Laohugou Glacier No. 12 was 402.96 m (3.99%) in total, and glacier length decreased to 9.7 km from 10.1 km. Reduction of glacier area and volume were the most obvious. From 1957 to 2015, glacier area and volume decreased by 1.54 km2 (7.03%) and 0.1816 km3, respectively. Reduction trend of terminus and area was slowing in 1950 - 1980s, even stable for a period in the mid-1980s, and then accelerated. Ice core analysis result and nearly meteorological station data shown an increasing trend of temperature in 1957 - 2015, it was a main reason of continuous retreating of Laohugou Glacier No.12.

Changes in Greenland’s peripheral glaciers linked to the North Atlantic Oscillation

Glaciers and ice caps peripheral to the main Greenland Ice Sheet contribute markedly to sea-level rise 1–3 . Their changes and variability, however, have been difficult to quantify on multi-decadal timescales due to an absence of long-term data 4 . Here, using historical aerial surveys, expedition photographs, spy satellite imagery and new remote-sensing products, we map glacier length fluctuations of approximately 350 peripheral glaciers and ice caps in East and West Greenland since 1890. Peripheral glaciers are found to have recently undergone a widespread and significant retreat at rates of 12.2 m per year and 16.6 m per year in East and West Greenland, respectively; these changes are exceeded in severity only by the early twentieth century post-Little-Ice-Age retreat. Regional changes in ice volume, as reflected by glacier length, are further shown to be related to changes in precipitation associated with the North Atlantic Oscillation (NAO), with a distinct east–west asymmetry; positive phases of the NAO increase accumulation, and thereby glacier growth, in the eastern periphery, whereas opposite effects are observed in the western periphery. Thus, with projected trends towards positive NAO in the future 5,6 , eastern peripheral glaciers may remain relatively stable, while western peripheral glaciers will continue to diminish. Combining historical aerial surveys, expedition photographs, and both spy and modern satellite imagery reveals a pronounced retreat of peripheral glaciers in east and west Greenland, linked to changes in precipitation associated with the NAO.

Multi-decadal variations in glacier flow velocity and the influencing factors of Urumqi Glacier No. 1 in Tianshan Mountains, Northwest China

Urumqi Glacier No. 1 is a representative glacier in the inland areas of Central Asia and is the only Chinese reference glacier in the World Glacier Monitoring Service. In this study, we explored multi-decadal variations in the flow velocity of the glacier and the influencing factors based on continuous field observations and path coefficient analysis. Results show that the glacier flow velocity decreased from 5.5 m/a in 1980/1981 to 3.3 m/a in 2010/2011. The annual variation in the direction of glacier flow velocity in the western branch and eastern branch was less than 1°–3°, and the change of glacier flow velocity in the western branch was more dramatic than that in the eastern branch. Glacier flow velocity was influenced by glacier morphology (including glacier area, glacier length, and ice thickness), glacier mass balance and local climate conditions (air temperature and precipitation), the glacier morphology being the leading factor. The long-term flow velocity data set of Urumqi Glacier No. 1 contributes to a better understanding of glacier dynamics within the context of climatic warming.

Slowing down the retreat of the Morteratsch glacier, Switzerland, by artificially produced summer snow: a feasibility study

Many large valley glaciers in the world are retreating at historically unprecedented rates. Also in the Alps, where warming over the past decades has been more than twice as large as the global mean, all major glaciers have retreated over distances of several kilometers over the past hundred years. The Morteratsch Glacier, Pontresina, Switzerland, is a major touristic attraction. Due to strong retreat, the lowest part of the glacier is getting out of sight from the gravel road that provided direct access to the glacier front. The Community of Pontresina has commissioned a preparatory study to find out if it is possible to slow down the retreat of the Morteratsch Glacier in an environmentally friendly way. In this article, we report on the outcome of such a study, based on a modeling approach. Our analysis is based on a 20-year weather station record from the lower part of the glacier, combined with calculations with a calibrated ice-flow model. We arrive at the conclusion that producing summer snow in the ablation zone over a larger area (typically 0.5 to 1 km2) may have a significant effect on the rate of retreat on a timescale of decades. We consider various scenarios of climate change: (i) no change, (ii) a rise of the equilibrium-line altitude (ELA) by 1, 2, and 4 m/yr. Projections of glacier length are calculated until the year 2100. It takes about 10 years before snow deposition in the higher ablation zone starts to affect the position of the glacier snout. For the case of modest warming, the difference in glacier length between the snow and no-snow experiments becomes 400 to 500 m within two decades.