Mean Specific Mass Balance Research Articles

Glacier mass balance estimation in Garhwal Himalaya using improved accumulation area ratio method.

Water requirements of the mountain communities living in the Himalaya are supported by snow and glacier melt. The availability of water from the source depends on numerous climatic and glacier parameters. One key parameter is mass balance, which helps to assess the glacier health and future water availability. We have used the improved accumulation area ratio (IAAR) method to estimate mass balance in Alaknanda and Bhagirathi basins, constituting 1055 glaciers covering ~1609 km2. The mean Equilibrium Line Altitude (ELA) of the Alaknanda and Bhagirathi basins are estimated as 6147 ± 130 and 5985 ± 130m.a.s.l, respectively. The mass balance is estimated using the accumulation area ratio (AAR)-mass balance relationship. The mean specific mass balance of the Alaknanda and Bhagirathi for 2001-2013 is estimated as -1.1 ± 0.03m.w.e.a-1 and -1.01 ± 0.07m.w.e.a-1, respectively. Total mass loss from the study area is calculated as ~21.4 ± 1.1Gt during this period. The loss of glaciers in the mountain area will increase the vulnerability of communities living in the region. It suggests a need for better adaptation strategies to improve the resilience of high mountain communities.

Reconstruction of the Historical (1750–2020) Mass Balance of Bordu, Kara-Batkak and Sary-Tor Glaciers in the Inner Tien Shan, Kyrgyzstan

The mean specific mass balance of a glacier represents the direct link between a glacier and the local climate. Hence, it is intensively monitored throughout the world. In the Kyrgyz Tien Shan, glaciers are of crucial importance with regard to water supply for the surrounding areas. It is therefore essential to know how these glaciers behave due to climate change and how they will evolve in the future. In the Soviet era, multiple glaciological monitoring programs were initiated but these were abandoned in the nineties. Recently, they have been re-established on several glaciers. In this study, a reconstruction of the mean specific mass balance of Bordu, Kara-Batkak and Sary-Tor glaciers is obtained using a surface energy mass balance model. The model is driven by temperature and precipitation data acquired by combining multiple datasets from meteorological stations in the vicinity of the glaciers and tree rings in the Kyrgyz Tien Shan between 1750 and 2020. Multi-annual mass balance measurements integrated over elevation bands of 100 m between 2013 and 2020 are used for calibration. A comparison with WGMS data for the second half of the 20th century is performed for Kara-Batkak glacier. The cumulative mass balances are also compared with geodetic mass balances reconstructed for different time periods. Generally, we find a close agreement, indicating a high confidence in the created mass balance series. The last 20 years show a negative mean specific mass balance except for 2008–2009 when a slightly positive mass balance was found. This indicates that the glaciers are currently in imbalance with the present climatic conditions in the area. For the reconstruction back to 1750, this study specifically highlights that it is essential to adapt the glacier geometry since the end of the Little Ice Age in order to not over- or underestimate the mean specific mass balance. The datasets created can be used to get a better insight into how climate change affects glaciers in the Inner Tien Shan and to model the future evolution of these glaciers as well as other glaciers in the region.

Thickness and geodetic mass balance changes for the Triglav Glacier (southeastern Alps) from 1952 to 2016

Various geodetic and lidar measurements performed on the Triglav Glacier (Julian Alps, Slovenia) make it possible to study not only the extent of the glacier but also changes in its thickness and volume. These measurements also make it possible to calculate the geodetic mass balance of the glacier. Thickness and volume changes were calculated using glacier area measurements from 1952, 1975, and 1992, and annually between 1999 and 2016. The mean thickness decreased from 39.2m in 1952 to 2.45m in 2012. The maximum thickness decreased from 48.3 m in 1952 to 5.2 m in 2007. The mean specific mass balance was calculated for the area of 1 hectare that the glacier covered in 2016. From 1952 to 2016, the annual specific mass balance was −0.45m w.e.a−1.

Large Losses in Glacier Area and Water Availability by the End of Twenty-First Century under High Emission Scenario, Satluj Basin, Himalaya

Glaciers in the Satluj river basin are likely to lose 53% and 81% of area by the end of the century, if climate change followed RCP 8.5 scenario of CNRMCM5 and GFDL-CM3 models respectively. The large variability in area loss can be due to difference in temperature and precipitation projections. Presently, Satluj basin has approximately 2000 glaciers, 1426 sq. km glacier area and 62.3 Gt glacier stored water. The current mean specific mass balance is –0.40 m.w.e. a–1. This will change to –0.42 and – 1.1 m.w.e. a–1 by 2090, if climate data of CNRM-CM5 and GFDL-CM3 are used respectively. We have used an extreme scenario of GFDL-CM3 model to assess the changes in the contribution of glacier melt to the Bhakra reservoir. Mass balance model suggests that glaciers are contributing 2 km3 a–1 out of 14 km3 of water. This will increase to 2.2 km3 a–1 by 2050, and then reduce to 1.5 km3 a–1 by the end of the century. In addition, loss in glacier area by the end of century, will also increase the vulnerability of mountain communities, suggesting need for better adaptation and water management practices.

Glacier mass balance and its potential impacts in the Altai Mountains over the period 1990–2011

The Altai Mountains contain 1281 glaciers covering an area of 1191km2. These glaciers have undergone significant changes in glacial length and area over the past decade. However, mass changes of these glaciers and their impacts remain poorly understood. Here we present surface mass balances of all glaciers in the region for the period 1990–2011, using a glacier mass-balance model forced by the outputs of a regional climate model. Our results indicate that the mean specific mass balance for the whole region is about −0.69mw.e.yr−1 over the entire period, and about 81.3% of these glaciers experience negative net mass balance. We detect an accelerated wastage of these glaciers in recent years, and marked differences in mass change and its sensitivity to climate change for different regions and size classes. In particular, higher mass loss and temperature sensitivity are observed for glaciers smaller than 0.5km2. In addition to temperature rise, a decrease in precipitation in the western part of the region and an increase in precipitation in the eastern part likely contribute to significant sub-region differences in mass loss. With significant glacier wastage, the contribution of all glaciers to regional water resources and sea-level change becomes larger than before, but may not be a potential threat to human populations through impacts on water availability.

Reconstruction of specific mass balance for glaciers in Western Himalaya using seasonal sensitivity characteristic(s)

Seasonal sensitivity characteristics (SSCs) were developed for Naradu, Shaune Garang, Gor Garang and Gara glaciers, Western Himalaya to quantify the changes in mean specific mass balance using monthly temperature and precipitation perturbations. The temperature sensitivities were observed high during summer (April–October) and precipitation sensitivities during winter months (November–March), respectively. The reconstructed mass balance correlates well with the field and remote sensing measurements, available between 1980 and 2014. Further, SSCs were used with the monthly mean temperatures and precipitation estimates of ERA 20CM ensemble climate reanalysis datasets to reconstruct the specific mass balance for a period of 110 years, between 1900 and 2010. Mass balance estimates suggest that the Shaune Garang, Gor-Garang and Gara glaciers have experienced both positive and negative mass balance, whereas the Naradu glacier has experienced only negative mass balance since 1900 AD. Further, a cumulative loss of \(-133 \pm 21.5\) m.w.e was estimated for four glaciers during the observation period. This study is the first record from Indian Himalaya in evaluating the mass balance characteristics over a century scale.

Application of a degree-day model for determination of mass balance of Urumqi Glacier No. 1, eastern Tianshan, China

In order to verify the feasibility and stability of a degree-day model on simulating the long time series of glacier mass balance, we apply a degree-day model to simulate the mass balance of Urumqi Glacier No. 1 for the period 1987/1988–2007/2008 based on temperature and precipitation data from a nearby climate station. The model is calibrated by simulating point measurements of mass balance, mass balance profiles, and mean specific mass balance during 1987/1988–1996/1997. The optimized parameters are obtained by using a least square method to make the model fit the measured mass balance through the model calibration. The model validation (1997/1998–2007/2008) indicates that the modeled results are in good agreement with the observations. The static mass balance sensitivity of Urumqi Glacier No. 1 is analyzed by computing the mass balance of the glacier for a temperature increase of 1 °C, with and without a 5% precipitation increase, and the values for the east branch are −0.80 and −0.87 m w.e. a−1·°C−1, respectively, and for the west branch, the values are −0.68 and −0.74 m w.e. a−1·°C−1, respectively. Moreover, the analysis of the parameter stability indicates that the parameters in the model determined from the current climate condition can be applied in the prediction of the future mass balance changes for the glacier and provide a reference for extending the model to other small glaciers in western China.

Estimating the mass balance of Vatnajökull, Iceland, from NOAA AVHRR imagery

AbstractWe investigate the possibility of obtaining the mass balance of Vatnajökull, Iceland, from US National Oceanic and Atmospheric Administration (NOAA) Advanced Very High Resolution Radiometer (AVHRR) albedo images for the years 1991-2002. De Ruyter de Wildt and others (2002) demonstrated that the mean potential absorbed radiation (〈Qpot,net〉) averaged over the melting season correlates well with the mean specific mass balance and that 〈Qpot,net〉 can be estimated from the evolution of the surface albedo. Here, we improve the retrieval method of de Ruyter de Wildt and others (2002) by introducing the more realistic 6S atmospheric transfer model and by adding the latest narrow-to-broadband (NTB) albedo conversion equations. Bidirectional reflectance distribution functions for both ice and snow are used where appropriate. We show that the choice of the NTB conversion equations greatly influences the calculated 〈Qpot,net〉. Measured mass balance correlates well with 〈Qpot,net〉 if enough cloud-free images can be found through the year and if the spatial variation in measured mass balances is high enough. The correlation coefficient for all drainage basins combined is 0.92, with a residual standard deviation of 0.18 m w.e. We present an estimated mass-balance series for the whole of Vatnajökull based on our findings. Switching between different AVHRR instruments over time may cause serious errors in the calculated mass balance.

A calibrated mass balance model for Vatnajökull, Iceland

Vatnajokull (Iceland) is the largest ice cap in the world where the energy and mass balance have been studied with good spatial and temporal resolution. In this paper we use these data to analyze the energy balance and to construct a calibrated and spatially distributed mass balance model. The incoming longwave radiation is best modeled as a function of meteorological variables in the free atmosphere just above the rel- atively thin katabatic layer, instead of those at the 2 m level. The ratio of changes in the 2 m temperature to changes in the free atmospheric temperature (the climate sensitivity) is smaller than 1. Therefore, when the bulk method is used to compute the turbulent fluxes, the 2 m temperature must be explicitly calculated. Otherwise the sensitivity of Vatnajokull to climatic change would be overestimated. When the model is forced with data from a permanent weather station not on the ice cap, it reproduces the observed mass balance reasonably well. Horizontal precipitation gradients over Vatnajokull are large, which results in a strongly varying sensitivity to external temperature changes over the ice cap. The mass balance and its sensitivity is thus highly dependent on local climatic conditions. For a temperature increase of 1 K and a simultaneous precipitation increase of 5.3%, the mean specific mass balance of Vatnajokull decreases by 0.56 m w.e.

Redistribution of snow and glacier mass balance from a hydrometeorological model

This paper reports on the extension of a hydrometeorological model of glacierized basins to incorporate a detailed account of glacier mass balance. In this mass balance module a constant fraction of snow fall is redistributed within the basin from ice free areas to the glacier areas. In the particular basin discussed here solid precipitation on the glacier surface is increased by a factor of 2.15 over the basin mean of each 100 m altitude interval. The resulting mass balance parameters like mean annual specific balance, b( h), balance gradients, equilibrium line altitude and accumulation area ratio are within the range of records from other glaciers. The sensitivity of these quantities to meteorological input and model tuning parameters is evaluated, e.g. the sensitivity of mean specific mass balance to mean basin temperature is of the order of 800 mm/K. Emphasis is placed on the net accumulation outside the glacier areas in years with positive mass balance.

Simulating annual glacier flow with a linear reservoir model

In this paper we present a numerical simulation of the observation that most alpine glaciers have reached peak velocities in the early 1980s followed by nearly exponential decay of velocity in the subsequent decade. We propose that similarity exists between precipitation and associated runoff hydrograph in a river basin on one side and annual mean specific mass balance of the accumulation area of alpine glaciers and ensuing changes in ice flow on the other side. The similarity is expressed in terms of a linear reservoir with fluctuating input where the year to year change of ice velocity is governed by two terms, a fraction of the velocity of the previous year as a recession term and the mean specific balance of the accumulation area of the current year as a driving term. The coefficients of these terms directly relate to the timescale, the mass balance/altitude profile, and the geometric scale of the glacier. The model is well supported by observations in the upper part of the glacier where surface elevation stays constant to within ±5 m over a 30 year period. There is no temporal trend in the agreement between observed and modeled horizontal velocities and no difference between phases of acceleration and phases of deceleration, which means that the model is generally valid for a given altitude on a given glacier.

Reconstruction of the mean specific mass balance of vatnajökull (iceland) with a seasonal sensitivity characteristic

We present a Seasonal Sensitivity Characteristic (SSC) of Vatnajökull (Iceland), which consists of the sensitivity of the mean specific mass balance to monthly perturbations in temperature and precipitation. The climate in Iceland is predominantly maritime (high precipitation) although often the polar air mass influences the area. This results in temperature sensitivities that are high in summer and nearly zero during the winter months. In contrast, precipitation sensitivities are high in winter and low in summer. We use the SSC of Vatnajökull as a reduced mass balance model, with which we reconstruct the mass balance of Vatnajökull since 1825. The reduced model shows that changes in temperature and precipitation like the ones observed both have a significant impact upon the mass balance. The reconstructed mass balance records for two Icelandic glaciers correlate very well with mass balance records that are extracted from length records with a linear inverse model. This places confidence in both the reduced (forward) mass balance model and in the inverse model, although the forward method produces larger mass balance variations than the inverse method. For the south of Vatnajökull we find that after 1900, the length record is well explained by temperature variations alone, while another Icelandic glacier (Sólheimajökull) was also influenced by precipitation variations.

Secular glacier mass balances derived from cumulative glacier length changes

Glacier mass changes are considered to represent natural key variables with respect to strategies for early detection of enhanced greenhouse effects on climate. The main problem, however, with interpreting worldwide glacier mass balance evolution concerns the question of representativity. One important key to deal with such uncertainties and to assess the spatio-temporal representativity of the few available measurements is the long-term change in cumulative glacier length. The mean specific mass balance determined from glacier length change data since 1900 shows considerable regional variability but centers around a mean value of about −0.25 m year−1 water equivalent.

Satellite retrieval of mass balance: comparing SAR images with albedo images and in situ mass-balance observations

AbstractWe present an analysis of many European Remote-sensing Satellite (ERS) synthetic aperture radar (SAR) images of Vatnajökull, Iceland, by comparing them with Advanced Very High Resolution Radiometer (AVHRR) images, mass-balance observations and modelled firn stratigraphy. Summer SAR and AVHRR images both detect the surface firn line (or the transient snow-line when it lies below the firn line) as a distinct boundary.Winter SAR images of Vatnajökull generally display the late-summer surface firn line, and often also a transition at a higher elevation that possibly reflects a subsurface continuation of the firn line. On some winter images the firn line is not adequately detected, possibly due to a shallow firn pack. We found no differences in back-scatter between melting snow and firn, and for most years no differences in reflectance either. For Vatnajökull, equilibrium-line altitude is therefore not a particularly useful estimator of the mean specific mass balance (Bm). Unlike albedo images, SAR images do not display interannual variations of the signal within the accumulation area that are clearly related toBm. Hence, SAR images of Vatnajökull contain less information aboutBmthan albedo images. However, for some drainage basins, mean transient snow-line/firn-line altitude during the melting season can be used to inferBm.

Model study of the spatial distribution of the energy and mass balance of Morteratschgletscher, Switzerland

AbstractTo investigate the spatial distribution of the energy- and mass-balance fluxes of a glacier, a two-dimensional mass-balance model was developed and applied to Morteratschgletscher, Switzerland. The model is driven by meteorological input from four synoptic weather stations located in the vicinity of Morteratschgletscher. The model results were compared to observations made on the glacier. The calculated mean specific mass balance is −0.47 m w.e. for 1999, and 0.23 m w.e. for 2000. Net shortwave radiation shows a minimum at around 3350 m a.s.l., due to the effects of shading, slope, aspect, reflection from the slopes, and obstruction of the sky. Ignoring these effects results in a 37% increase in the annual incoming shortwave radiation on the glacier, causing 0.34 m w.e. more ablation. A 1°C change in the air temperature results in a shift of 0.67 m w.e. in the mean specific mass balance, while altering the precipitation by 10% causes a change of 0.17 m w.e.

Remote sensing of the albedo and detection of the slush line on the Greenland ice sheet

Advanced very high resolution radiometer images of a section of the Greenland ice sheet (western part between 64.5° and 70.5°N with a size of 667 (N‐S) by 700 (W‐E) km) were processed in order to retrieve the surface albedo. The images were for the summer seasons of 1990–1997 inclusive, and results were compared to simultaneous mass balance measurements carried out along the transect (67°N). The main findings are as follows: First, many images show a distinct transition from low spatial variability of the albedo at higher elevations to higher spatial variability of the albedo at lower elevations. It is argued that these transitions most likely correspond to transitions at the surface (“slush line,” in short) from the area that is uniformly covered by snow to a mosaic of snow patches, slush, and ice. Second, 70% of the interannual variations in the mean specific mass balance can be explained by interannual variations in the maximum elevation of the slush line (i.e., the “slush limit”). However, a higher percentage (82%) can be explained by interannual variations in the sum of positive degree‐days. Third, in 3 years with a relatively large amount of melt the inland migration of the slush line stopped or slowed considerably down at a fixed distance from the ice sheet margin. We believe that this so‐called “maximum slush line” coincides with an abrupt change in the density profile. The maximum slush line forms an important limitation for the use of satellite data to monitor interannual variations in the mass balance. Its position is a climate indicator and was determined for the entire section of the Greenland ice sheet investigated.

Present and future mass balance of the ice sheets simulated with GCM

A high-resolution GCM ECHAM3 T106 was used to simulate the climates of the present and of the future under doubled CO2The ECHAM3 T106 was integrated for an equivalent time of 5 years (1) with the observed SST of the 1980s and (2) with the SST for the 2 × CO2climate generated from the ECHAM1 T21 coupled transient experiment. The main motivation for using the GCM to simulate the mass balance is the level of skill in simulating precipitation and accumulation recently achieved in the high-resolution GCM experiment. The ablation is computed, based on the GCM internal surface fluxes and the temperature/ablation relationship formulated on the Greenland field data. The two ice sheets show very different reactions towards doubling the CO2. As the decrease in accumulation and the increase in ablation in Greenland cause an annual mean specific mass balance of −225 mm (eq. −390 km3), the increase in accumulation and virtually non-melt conditions in Antarctica result in a mean annual specific mass balance of + 23 mm (eq. + 325 km3). The sum of the mass balance on both ice sheets is equivalent to the annual sea-level rise of 0.2 mm. This experiment shows that other mechanisms for sea-level change, such as the thermal expansion of the sea water and the melt of small mountain glaciers, will remain important in the coming century.

Present and future mass balance of the ice sheets simulated with GCM

A high-resolution GCM ECHAM3 T106 was used to simulate the climates of the present and of the future under doubled CO2 The ECHAM3 T106 was integrated for an equivalent time of 5 years (1) with the observed SST of the 1980s and (2) with the SST for the 2 × CO2 climate generated from the ECHAM1 T21 coupled transient experiment. The main motivation for using the GCM to simulate the mass balance is the level of skill in simulating precipitation and accumulation recently achieved in the high-resolution GCM experiment. The ablation is computed, based on the GCM internal surface fluxes and the temperature/ablation relationship formulated on the Greenland field data. The two ice sheets show very different reactions towards doubling the CO2. As the decrease in accumulation and the increase in ablation in Greenland cause an annual mean specific mass balance of −225 mm (eq. −390 km3), the increase in accumulation and virtually non-melt conditions in Antarctica result in a mean annual specific mass balance of + 23 mm (eq. + 325 km3). The sum of the mass balance on both ice sheets is equivalent to the annual sea-level rise of 0.2 mm. This experiment shows that other mechanisms for sea-level change, such as the thermal expansion of the sea water and the melt of small mountain glaciers, will remain important in the coming century.