Annual Glacier Mass Balance Research Articles

Geodetic reanalysis of annual glaciological mass balances (2001–2011) of Hintereisferner, Austria

Abstract. This study presents a reanalysis of the glaciologically obtained annual glacier mass balances at Hintereisferner, Ötztal Alps, Austria, for the period 2001–2011. The reanalysis is accomplished through a comparison with geodetically derived mass changes, using annual high-resolution airborne laser scanning (ALS). The grid-based adjustments for the method-inherent differences are discussed along with associated uncertainties and discrepancies of the two methods of mass balance measurements. A statistical comparison of the two datasets shows no significant difference for seven annual, as well as the cumulative, mass changes over the 10-year record. Yet, the statistical view hides significant differences in the mass balance years 2002/03 (glaciological minus geodetic records = +0.92 m w.e.), 2005/06 (+0.60 m w.e.), and 2006/07 (−0.45 m w.e.). We conclude that exceptional meteorological conditions can render the usual glaciological observational network inadequate. Furthermore, we consider that ALS data reliably reproduce the annual mass balance and can be seen as validation or calibration tools for the glaciological method.

Spatiotemporal variability of Canadian High Arctic glacier surface albedo from MODIS data, 2001–2016

Abstract. Inter-annual variations and longer-term trends in the annual mass balance of glaciers in Canada's Queen Elizabeth Islands (QEI) are largely attributable to changes in summer melt. The largest source of melt energy in the QEI in summer is net shortwave radiation, which is modulated by changes in glacier surface albedo. We used measurements from the Moderate Resolution Imaging Spectroradiometer (MODIS) sensors to investigate large-scale spatial patterns, temporal trends, and variability in the summer surface albedo of QEI glaciers from 2001 to 2016. Mean summer black-sky shortwave broadband albedo (BSA) decreased at a rate of 0.029±0.025 decade−1 over that period. Larger reductions in BSA occurred in July (−0.050±0.031 decade−1). No change in BSA was observed in either June or August. Most of the decrease in BSA, which was greatest at lower elevations around the margins of the ice masses, occurred between 2007 and 2012, when mean summer BSA was anomalously low. The first principal component of the 16-year record of mean summer BSA was well correlated with the mean summer North Atlantic Oscillation index, except in 2006, 2010, and 2016, when the mean summer BSA appears to have been dominated by the August BSA. During the period 2001–2016, the mean summer land surface temperature (LST) over the QEI glaciers and ice caps increased by 0.049±0.038 °C yr−1, and the BSA record was negatively correlated (r: −0.86) with the LST record, indicative of a positive ice-albedo feedback that would increase rates of mass loss from the QEI glaciers.

Glacier Mass-Balance Variation in China during the Past Half Century

The aim of this study is to investigate the impact of temperature trend on glacier-mass balance, snow density, snowmelt, snow depth and runoff by using observations of nine glacier stations that covered most of the China over the period of 1979-2013. Trend analysis showed an increasing trend of temperature on all of the selected stations. On an average, temperature (?C) was increasing at the rate of 0.46/10a. The increasing trend of temperature showed a negative relationship with annual glacier-mass balance on most of the stations and caused a decrease in annual balance. Results of Pearson’s correlation analysis showed a highly significant negative correlation between temperature and snow density (correlation coefficient (CC = ?0.661 at 0.01 significance level). There was a significant positive correlation between temperature and snowmelt (CC = 0.532 at 0.01 significance level). There was a significant negative correlation between temperature and snow depth (corre-lation coefficient (CC = ?0.342 at 0.05 significance level). Moreover, there was a significant positive correlation between temperature and runoff (CC = 0.586 at 0.01 significance level). Increasing trend of temperature caused an increasing trend of annual snowmelt and runoff anomaly% at the rate of 24.82/10a and 9.87/10a, respectively. On the other hand, a declining trend in annual snow density and snow depth anomaly% was found at a rate of ?5.32/10a and ?1.93/10a, respectively. We concluded that the snow density, snowmelt and runoff are significantly sensitive to temperature in China. This contribution has provided information for further understanding of glacier variation and its influencing factors.

Melting Characteristics of Snow Cover on Tidewater Glaciers in Hornsund Fjord, Svalbard

In recent years, the Svalbard area, especially its southern section, has been characterised by an exceptionally thin snow cover, which has a significant impact of the annual mass balance of glaciers. The objective of this study was to determine melting processes of the snow cover deposited on 11 glaciers that terminate into Hornsund Fjord during the melting period of 2014. The study included analyses of snow pits and snow cores, meteorological data collected from automatic weather stations and Polish Polar Station Hornsund, and supervised classification of six Landsat 8 images for assessing the progress of snow cover melting. The calculated Snow-Covered Area (SCA) varied from 98% at the beginning of the melting season to 43% at the end of August. The melting vertical gradient on Hansbreen was −0.34 m 100 m−1, leading to surface melting of −1.4 cm water equivalent (w.e.) day−1 in the ablation zone (c. 200 m a.s.l. (above sea level)) and −0.7 cm w.e. day−1 in the accumulation zone (c. 400 m a.s.l.). Furthermore, the study identified several observed features such as low snow depth in the accumulation zone of the Hornsund glaciers, a large proportion of the snow layers (12–27%) produced by rain-on-snow events, and a frequent occurrence of summer thermal inversions (80% annually), indicating that the area is experiencing intensive climate changes.

An estimate of glacier mass balance for the Chandra basin, western Himalaya, for the period 1984–2012

ABSTRACTAn improved understanding of fresh water stored in the Himalaya is crucial for water resource management in South Asia and can be inferred from glacier mass-balance estimates. However, field investigations in the rugged Himalaya are limited to a few individual glaciers and short duration. Therefore, we have recently developed an approach that combines satellite-derived snowlines, a temperature-index melt model and the accumulation-area ratio method to estimate annual mass balance of glaciers at basin scale and for a long period. In this investigation, the mass balance of 146 glaciers in the Chandra basin, western Himalaya, is estimated from 1984 to 2012. We estimate the trend in equilibrium line altitude of the basin as +113 m decade−1and the mean mass balance as −0.61 ± 0.46 m w.e. a−1. Our basin-wide mass-balance estimates are in agreement with the geodetic method during 1999–2012. Sensitivity analysis suggests that a 20% increase in precipitation can offset changes in mass balance for a 1 °C temperature rise. A water loss of 18% of the total basin volume is estimated, and 67% for small and low-altitude glaciers during 1984–2012, indicating a looming water scarcity crisis for villages in this valley.

The importance of aspect for modelling the hydrological response in a glacier catchment in Central Asia

AbstractUnderstanding how explicit consideration of topographic information influences hydrological model performance and upscaling in glacier dominated catchments remains underexplored. In this study, the Urumqi glacier no. 1 catchment in northwest China, with 52% of the area covered by glaciers, was selected as study site. A conceptual glacier‐hydrological model was developed and tested to systematically, simultaneously, and robustly reproduce the hydrograph, separate the discharge into contributions from glacier and nonglacier parts of the catchment, and establish estimates of the annual glacier mass balance, the annual equilibrium line altitude, and the daily catchment snow water equivalent. This was done by extending and adapting a recently proposed landscape‐based semidistributed conceptual hydrological model (FLEX‐Topo) to represent glacier and snowmelt processes. The adapted model, FLEXG, allows to explicitly account for the influence of topography, that is, elevation and aspect, on the distribution of temperature and precipitation and thus on melt dynamics. It is shown that the model can not only reproduce long‐term runoff observations but also variations in glacier and snow cover. Furthermore, FLEXG was successfully transferred and up‐scaled to a larger catchment exclusively by adjusting the areal proportions of elevation and aspect without the need for further calibration. This underlines the value of topographic information to meaningfully represent the dominant hydrological processes in the region and is further exacerbated by comparing the model to a model formulation that does not account for differences in aspect (FLEXG,nA) and which, in spite of satisfactorily reproducing the observed hydrograph, does not capture the influence of spatial variability of snow and ice, which as a consequence reduces model transferability. This highlights the importance of accounting for topography and landscape heterogeneity in conceptual hydrological models in mountainous and snow‐, and glacier‐dominated regions.

Modeling Glacier Mass Balance and Runoff in the Koxkar River Basin on the South Slope of the Tianshan Mountains, China, from 1959 to 2009

Water resources provided by alpine glaciers are an important pillar for people in the arid regions of west China. In this study, the Hydrologiska Byrans Vattenavdelning (HBV) light model was applied to simulate glacier mass balance (GMB) and runoff in the Koxkar River Basin (KRB) on the south slope of Mount Tumur, in the western Tianshan Mountains. Daily temperature and precipitation were calculated by multiple linear regressions and gradient-inverse distance weighting, respectively, based on in-situ observed data by automatic weather stations (AWSs) in the Koxkar River Basin (KRB; 2007–2009) and four meteorological stations neighboring the basin (1959–2009). Observed daily air temperature and precipitation were input into HBV model. The runoff data in 2007/2008 and 2008/2009 were used to calibrate and validate the model in 2009/2010 and 2010/2011. Generally, the model simulated runoff very well. The annual glacier mass balance and runoff were calculated by the HBV model and were driven by interpolated meteorological data between 1959 and 2009. The calculated glacier mass balances were reasonable, and were compared with nearby glaciers. The results indicate the decreasing trend of mass balance in the Koxkar Glacier, with an average value of ablation of −370.4 mm·a−1 between 1959 and 2009. The annual runoff showed an increasing trend (5.51 mm·a−1). Further analysis showed that the runoff is more sensitive to temperature than precipitation in KRB.

Climate and surface mass balance of Mocho Glacier, Chilean Lake District, 40°S

ABSTRACTWe present climate data, direct surface mass balance (SMB) observations and model results for Mocho Glacier in the Chilean Lake District. Mean annual temperature on a nunatak of Mocho Glacier at an elevation of ~2000 m was +2.6°C in 2006–15 and mean annual precipitation in Puerto Fuy (13 km from the glacier, at an elevation of 600 m) was 4000 mm for the same period. High interannual variations in the SMB of Mocho Glacier were observed. A simple SMB model is able to reproduce the observed annual variations in SMB, but fails to predict the steep observed mass-balance gradient. The average of the measured annual glacier mass balances in the four hydrological years 2009/10–2012/13 was −0.90 m w.e. a−1and the average modelled annual glacier mass balance 2006/07–2014/15 was −1.05 m w.e. a−1. The observed distributed ablation shows a clear altitudinal dependency, while accumulation is determined by patterns of snow drift as well. These patterns are only poorly represented in the model and have to be included in order to be able to reproduce a realistic SMB map of the glacier.

Slight mass loss revealed by reanalyzing glacier mass-balance observations on Glaciar Antisana 15α (inner tropics) during the 1995–2012 period

ABSTRACTIn this paper, we reanalyze the glacier mass balance on Glaciar Antisana 15α over the 1995–2012 period. Annual glacier mass balances were quantified on the basis of monthly glaciological measurements using an adaptation of Lliboutry's statistical approach. The geodetic mass balance was computed between 1997 and 2009 giving a cumulative balance of −1.39 ± 1.97 m w.e. and a slightly negative adjusted annual glaciological mass balance (−0.12 ± 0.16 m w.e. a−1). Despite a careful analysis of uncertainties, we found a large discrepancy between the cumulative glaciological and the geodetic mass balances over the common period, of 4.66 m w.e. This discrepancy can mainly be explained by underestimated net accumulation in the glacier upper reaches, which could be due to the peculiar climate conditions of the equatorial zone with year round accumulation, thereby preventing clear identification of annual layers. An increase of ~70% in measured rates of net accumulation would be needed to balance the glaciological and geodetic mass balances; a hypothesis confirmed by estimated ice flux in the vicinity of the ELA. Consequently, the vertical gradient of precipitation may be higher than previously estimated and the accumulation processes (including the role of frost deposition) need to be carefully analyzed.

Simulation and reconstruction of parameters of streamflow and glacier mass balance in the Northern Caucasus

Для исследования и решения поставленной проблемы использована обширная база факторов прямо (разнообразные сведения о климате) или косвенно (индексы ширины и максимальной плотности древесных колец) характеризующих условия формирования годового и сезонного стока рек и составляющих баланса массы ледников на Северном Кавказе. На основе этой информации получен и проверен на независимых данных ряд новых формул для расчёта сезонного стока р. Терек на семи гидропостах в 1901–2010 гг.; оценена также значимость различных аргументов в этих формулах для описания изменчивости функции. Впервые получены уравнения связи между высотой линии равновесия ELA в конце периода абляции, индексом площади аккумуляции AAR и составляющими годового баланса массы Bn, Bw и Bs на ледниках Джанкуат и Гарабаши. Разработана методика региональных расчётов средних величин аккумуляции на ледниках по данным об абляции и ELA.

Seasonal changes in surface albedo of Himalayan glaciers from MODIS data and links with the annual mass balance

Abstract. Few glaciological field data are available on glaciers in the Hindu Kush–Karakoram–Himalayan (HKH) region, and remote sensing data are thus critical for glacier studies in this region. The main objectives of this study are to document, using satellite images, the seasonal changes of surface albedo for two Himalayan glaciers, Chhota Shigri Glacier (Himachal Pradesh, India) and Mera Glacier (Everest region, Nepal), and to reconstruct the annual mass balance of these glaciers based on the albedo data. Albedo is retrieved from Moderate Resolution Imaging Spectroradiometer (MODIS) images, and evaluated using ground based measurements. At both sites, we find high coefficients of determination between annual minimum albedo averaged over the glacier (AMAAG) and glacier-wide annual mass balance (Ba) measured with the glaciological method (R2 = 0.75). At Chhota Shigri Glacier, the relation between AMAAG found at the end of the ablation season and Ba suggests that AMAAG can be used as a proxy for the maximum snow line altitude or equilibrium line altitude (ELA) on winter-accumulation-type glaciers in the Himalayas. However, for the summer-accumulation-type Mera Glacier, our approach relied on the hypothesis that ELA information is preserved during the monsoon. At Mera Glacier, cloud obscuration and snow accumulation limits the detection of albedo during the monsoon, but snow redistribution and sublimation in the post-monsoon period allows for the calculation of AMAAG. Reconstructed Ba at Chhota Shigri Glacier agrees with mass balances previously reconstructed using a positive degree-day method. Reconstructed Ba at Mera Glacier is affected by heavy cloud cover during the monsoon, which systematically limited our ability to observe AMAAG at the end of the melting period. In addition, the relation between AMAAG and Ba is constrained over a shorter time period for Mera Glacier (6 years) than for Chhota Shigri Glacier (11 years). Thus the mass balance reconstruction is less robust for Mera Glacier than for Chhota Shigri Glacier. However our method shows promising results and may be used to reconstruct the annual mass balance of glaciers with contrasted seasonal cycles in the western part of the HKH mountain range since the early 2000s when MODIS images became available.

Possibility of using remote sensing data for glaciological calculations and monitoring

Altitude and areal characteristics of glaciation of the Earth, as well as annual ELA and AAR values for a limited number of glaciers can be found in references [10, 15, 16, 18, 29]. According to these data, the analysis of the relations between ELA, AAR, annual mass balance of glaciers and its components was performed for use in the remote monitoring of glaciation. Appropriate sample included 45 to 66 glaciers located mainly in Eurasia, at mean weighted altitudes Z med from 520 m to 4253 m above sea level. The existence of close and stable spatial relations AAR = f ( Bn ) and AAR = f (ELA) (see Table 1) allows, ultimately obtain local or regional estimates of glacier mass balance. In 1957, the area of the moraine on the glaciers of the Pamir was 320 km 2 , or 4.8% of the total area of glaciers in the region, and after ~ 20 years it has increased to 644 km 2 or 10.7% [10]. In this paper we used photos of glaciers Medvezhiy and Bivachny in late August 2007 and 2012 from the ISS. Ground resolution is of 3–5 meters. Photos were transformed into WGS projection and tied to a topographic map 1:50 000. Altitudinal interval of moraines propagation on glaciers Medvezhiy and Bivachny in 2007–2012 was equal to, respectively: 3000–5000 and 3400–4800 m above sea level. It was revealed increase of total area of the moraine on these glaciers for the years 1975– 2007. Analysis of the content and quality of the main sources of global and regional information about modern glaciation of the Earth shows that without additional thematic processing they are not suitable for monitoring the dynamics of glaciers in the major river basins and use on a par with the existing data on precipitation, temperature, humidity, cloud cover and other climatic characteristics. Additional processing should be provided to exclude asynchronies in morphometric parameters. This will reduce errors in glaciological interpretation of satellite images and improve the quality of spatial extrapolation of meteorological data. Examples are given of determining the spectral albedo of glacier surface, using ENVI software and remote sensing data from Landsat 7 ETM+ and TERRA. Application of the methods for determining the albedo on the one hand creates additional opportunities for remote monitoring of glaciers, on the other – provides calculation different types of melted glacier surface as a function of absorbed solar radiation.

Juneau Icefield Mass Balance Program 1946–2011

Abstract. The annual surface mass balance records of the Lemon Creek Glacier and Taku Glacier observed by the Juneau Icefield Research Program are the longest continuous glacier annual mass balance data sets in North America. Annual surface mass balance (Ba) measured on Taku Glacier averaged +0.40 m a−1 from 1946–1985, and −0.08 m a−1 from 1986–2011. The recent annual mass balance decline has resulted in the cessation of the long-term thickening of the glacier. Mean Ba on Lemon Creek Glacier has declined from −0.30 m a−1 for the 1953–1985 period to −0.60 m a−1 during the 1986–2011 period. The cumulative change in annual surface mass balance is −26.6 m water equivalent, a 29 m of ice thinning over the 55 yr. Snow-pit measurements spanning the accumulation zone, and probing transects above the transient snow line (TSL) on Taku Glacier, indicate a consistent surface mass balance gradient from year to year. Observations of the rate of TSL rise on Lemon Creek Glacier and Taku Glacier indicate a comparatively consistent migration rate of 3.8 to 4.1 m d−1. The relationship between TSL on Lemon Creek Glacier and Taku Glacier to other Juneau Icefield glaciers (Norris, Mendenhall, Herbert, and Eagle) is strong, with correlations exceeding 0.82 in all cases. doi:10.5065/D6NZ85N3

Linking glacier annual mass balance and glacier albedo retrieved from MODIS data

Abstract. Albedo is one of the variables controlling the mass balance of temperate glaciers. Multispectral imagers, such as MODerate Imaging Spectroradiometer (MODIS) on board the TERRA and AQUA satellites, provide a means to monitor glacier surface albedo. In this study, different methods to retrieve broadband glacier surface albedo from MODIS data are compared. The effect of multiple reflections due to the rugged topography and of the anisotropic reflection of snow and ice are particularly investigated. The methods are tested on the Saint Sorlin Glacier (Grandes Rousses area, French Alps). The accuracy of the retrieved albedo is estimated using both field measurements, at two automatic weather stations located on the glacier, and albedo values derived from terrestrial photographs. For summers 2008 and 2009, the root mean square deviation (RMSD) between field measurements and the broadband albedo retrieved from MODIS data at 250 m spatial resolution was found to be 0.052 or about 10% relative error. The RMSD estimated for the MOD10 daily albedo product is about three times higher. One decade (2000–2009) of MODIS data were then processed to create a time series of albedo maps of Saint Sorlin Glacier during the ablation season. The annual mass balance of Saint Sorlin Glacier was compared with the minimum albedo value (average over the whole glacier surface) observed with MODIS during the ablation season. A strong linear correlation exists between the two variables. Furthermore, the date when the average albedo of the whole glacier reaches a minimum closely corresponds to the period when the snow line is located at its highest elevation, thus when the snow line is a good indicator of the glacier equilibrium line. This indicates that this strong correlation results from the fact that the minimal average albedo values of the glacier contains considerable information regarding the relative share of areal surfaces between the ablation zone (i.e. ice with generally low albedo values) and the accumulation zone (i.e. snow with a relatively high albedo). As a consequence, the monitoring of the glacier surface albedo using MODIS data can provide a useful means to evaluate the interannual variability of the glacier mass balance. Finally, the albedo in the ablation area of Saint Sorlin Glacier does not exhibit any decreasing trend over the study period, contrasting with the results obtained on Morteratsch Glacier in the Swiss Alps.

Spatial and temporal variability of annual glacier equilibrium line altitudes in the Southern Alps, New Zealand

Assessments of the contribution of meltwater to sea-level rise from mountain glaciers cannot presently account for the considerable spatial inter-catchment and temporal inter-annual variations in annual net glacier mass balance. We therefore analyse annual equilibrium line altitudes (ELAs) to infer the controls on annual net glacier mass-balance variability for 34 glaciers in the central Southern Alps, New Zealand. Elevation, curvature and mean solar radiation receipt (both direct and indirect) during the ablation season can in combination account for up to 95% of the (temporal) variability in the long term ELA and up to c. 85% for a given year. It appears that long-term glacier net mass balance in the Southern Alps is controlled by ablation processes as a function of air temperature which decreases with elevation, and shortwave radiation which causes a positive feedback in ablation by reducing snow and ice cover and increasing albedo. In detail however, the degree to which local topographic variables can explain the differences in (i) the patterns and (ii) in the magnitudes of departures from the trend varies considerably from year to year and across the study region. At least 15–35% of annual ELA temporal variability is apparently associated with regional weather patterns. Our basic quantification of the interaction on multiple scales of topographic influences on annual ELA and ELAo (steady-state ELA) has implications for understanding inter- and intra-catchment variability in glacier responses to climatic change.

Reconstructions of annual discharge and equilibrium line altitude of glaciers at Qilian Shan, northwest China, from 1978 to 2002

AbstractDischarge was calculated from a mountainous area, including discharge from glaciers, in the Qilian Shan (Qilian Mountains) of northwest China. The studied Yingluoxia basin is 9983 km2 in area, with glaciers making up 0·3% of the basin. The calculation method was based on the heat balance, requiring only daily temperature and precipitation. Calculated annual discharge from the basin corresponded well with the observed data. Calculated annual discharge from glaciers was 3·6% of the total discharge from the basin.The temporal trend of the calculated equilibrium line altitude (ELA) at the July 1st Glacier (western side of the Yingluoxia basin) was similar to that of the observed ELA. The calculated annual mass balance of glaciers within the Yingluoxia basin has a larger negative value than the other glaciers in China, as the ratio of accumulation area to the total glacier area in the Yingluoxia basin is much lower than in neighbouring basins to the west. Copyright © 2010 John Wiley & Sons, Ltd.

Glacier runoff variation and its influence on river runoff during 1961–2006 in the Tarim River Basin, China

Using monthly precipitation and temperature data from national meteorological stations, 90 m resolution DEM and a digital vector map of modern glaciers from the Chinese Glacier Inventory, the glacier mass balance and glacier runoff in the Tarim River Basin (TRB), China, were estimated based on a monthly degree-day model for 1961–2006. The results suggest that the modified monthly degree-day model can simulate the long-term changes in glacier mass balance and glacier runoff, which have been confirmed by short-term observation data and other results in literatures. The characteristics and trends of mass balance and glacier runoff variation were analyzed. It was found that the mean annual glacier mass balance during 1961–2006 was −139.2 mm per year and the cumulative mass balance over the 46 year period was −6.4 m in the TRB. The glacier mass balance displayed a clear decreasing trend over the entire TRB during 1961–2006. The average annual glacier runoff in the TRB was 144.16×108 m3 for 1961–2006. The results also show that glacier runoff has increased in the last 46 years, especially since the 1990s with 85.7% of the increased river flow being derived from the increased glacier runoff caused by loss of ice mass. Over the entire TRB, glacier runoff accounts for 41.5% of the total river flow during 1961–2006. The impact of glacier runoff on river flow has increased in the TRB as a result of glacier shrinkage.

On the value of glacier mass balances for hydrological model calibration

Hydrological modelling of glacierized catchments is challenging because internal inconsistencies might be hidden due to ice melt which represents an additional source of water. This is even more significant if there are no data available to evaluate model simulations, as is often the case in remote areas. On the other hand, these glacierized catchments are important source regions for water, and detailed knowledge of water availability is a prerequisite for good resource management strategies. An important question is how useful a limited amount of data might be for model applications. Therefore, in this study the predictive power of limited discharge measurements, mass balance observations and the combination of both was analyzed by means of Monte Carlo analyses with multi-criteria model performance evaluation. Ensembles of 100 parameter sets were selected by evaluating the simulations based on a limited number of discharge measurements, glacier mass balance, and the combination of discharge and mass balance observations. Then the ensemble simulation of runoff was evaluated for the entire runoff series. The result indicated that a single annual glacier mass balance observation contained useful information to constrain hydrological models. Combining mass balance observations with a few discharge data improved the internal consistency and significantly reduced the uncertainties compared to parameter set selections based on discharge measurements alone. To obtain good ensemble predictions, information on discharge was required for at least 3 days during the melting season. This demonstrated that the timing of runoff measurements is important for the information contained in these data.

A simple method of simulating the future frontal position of Briksdalsbreen, western Norway

To simulate future mass balance and frontal variations of Briksdalsbreen in western Norway, a degree-day model based on temperature and precipitation data from Bergen has been used. Briksdalsbreen is a steep, western outlet glacier from Jostedalsbreen. The calculated relationship between annual glacier front variation and mass balance gives best correlation with a frontal time lag of 3 years, which is in accordance with previous studies. Climate scenarios from the Norwegian RegClim project have been implemented in the model. Applying the RegClim future climate (summer temperature and winter precipitation) scenarios, our calculations indicate that Briksdalsbreen may retreat 2—2.5 km from the 1963 position within the termination of the twenty-first century. The main icefall may thus disappear and the upper part of the glacier will exist as a plateau glacier. The accumulation area may thus consist of a small plateau and the glacier will therefore be sensitive to mass balance changes. Work is in progress to implement a dynamic glacier model for future studies.

The ‘benchmark glacier’ concept – does it work? Lessons from the North Cascade Range, USA

AbstractBenchmark glaciers were established in many alpine areas during the 1960s as part of the International Hydrological Decade to represent ‘typical’ mass and energy processes on glaciers in different climatic regions around the world. These glaciers have received new interest in the past decade because they are used to infer the contribution of alpine glacier wastage to global sea-level rise. We compare South Cascade Glacier, the benchmark glacier for the northwest contiguous USA, and four other secondary glaciers, against the topographic, area and mass changes of 321 glaciers in the surrounding region. Results show that South Cascade Glacier is unusually large, of lower slope and much larger area and had mass losses greater than most other glaciers in the region. Three of the four secondary glaciers were much more typical. Year-to-year variations in mass balance were highly correlated between all five glaciers, and any of these glaciers, including the benchmark glacier, could be used to infer temporal mass variations in the region. However, the use of South Cascade Glacier to estimate area/mass losses for the region would result in overestimating the area/mass changes by a factor of three. Local differences in the magnitude of annual glacier mass balance control cumulative mass changes and area changes. There appears to be no way to select a representative glacier a priori, and knowledge of changes over the region is required. Therefore, there may be great uncertainty in estimates of sea-level rise from the wastage of alpine glaciers based on the benchmark approach. We recommend re-evaluation of regional glacier mass changes inferred from benchmark glaciers in critical regions.