Regional Glacier Mass Balance Research Articles

Spatiotemporal Variations of Glacier Mass Balance in the Tomur Peak Region Based on Multi-Source Altimetry Remote Sensing Data

Alpine glaciers are sensitive indicators of regional climate change, which can affect regional ecological stability and social development. Variations in glacier mass balance (GMB) are an important parameter in studying glacier change. In this study, data from the Ice, Cloud, and Land Elevation Satellite-1 (ICESat-1), the Ice, Cloud, and Land Elevation Satellite-2 (ICESat-2), and CryoSat-2 (Ku-band) were combined, and high-resolution ALOS DEM was employed to denoise. After that, the polynomial fitting method was used to analyze the characteristics of glacier surface elevation (GSE) variations from 2003–2020 in the Tomur Peak Region of the Central Asian Tianshan Mountains and the regional GMB was calculated. Research results showed that: (1) From 2003–2020, the GSE of the Tomur Peak Region had an overall −8.95 ± 4.48 m variation, the average rate of which was −0.53 ± 0.26 m/yr (/yr is /year). Overall, elevations of most glaciers in the Tomur Peak Region had downward trends, with a rate of change of −0.5 to 0 m/yr. The fastest rate of elevation decline in the Koxkar Glacier Tongue was −1.5 m/yr. The elevation of some altimetric points in the Eastern Tomur Peak Region showed a rising state, with a maximum rate of variation of 1.0 m/yr. (2) From 2003–2020, the average GMB in the Tomur Peak Region was −1.51 ± 0.04 Gt/yr. In the region of elevation below 4000 m, small glaciers dominated, with a GMB of −0.61 ± 0.04 Gt/yr. With increasing elevation, the melting rate of glaciers gradually slowed down, but overall, the mass balance remained in a state of decline. (3) Climate was the main driving factor of GMB change in the study area. From 2003–2020, in the Tomur Peak Region, the average annual temperature continued to increase at a rate of 0.04 ± 0.02 °C/yr, and this was the main influencing factor for the negative GMB in the Tomur Peak Region. In the same period, the annual precipitation showed a rising trend with a linear variation rate of 0.12 ± 0.06 mm/yr, and the rising precipitation was the influencing factor for the gradually slowing change in the GMB in the study area.

Glacier Mass Balance Changes Over the Turgen Daban Range, Western Qilian Shan, From 1966/75 to 2020

Extensive efforts for quantifying regional glacier mass balance in the Qilian Mountains have been made using the geodetic method, but these estimations were rarely extended back to the period before 2000. This study presents glacier mass budgets in the Turgen Daban Range, over the western Qilian Mountain, from 1966/75 to 2020 by means of the digital elevation models generated by the topographic maps and ASTER images. The results show that the glacier mass decreased by −18.79 ± 12.48 m w.e. during the past 50 years. The average mass loss rate is estimated to be −0.19 ± 0.08 m w.e.a−1 for the 1966/75-2006 period and −0.45 ± 0.17 m w.e.a−1 during 2006–2020, respectively, suggesting a remarkable acceleration of glacier mass loss. This may be attributable to the significant increase in air temperature and the insignificant precipitation increase which cannot offset glacier melting caused by increased temperature. Due to the melting and shrinking of glaciers, the area of glacial lakes increases by 2.83 km2 from 1987 to 2020.

Regional and Altitude-Dependent Estimate of the SRTM C/X-Band Radar Penetration Difference on High Mountain Asia Glaciers

Radar penetration correction is essential for accurately estimating glacier mass balance when using the geodetic methods based on the radar-derived digital elevation model (DEM). Due to heterogeneous snow distribution and snowpack properties, the radar penetration depth varies by region and is basically dependent on the altitudes. However, a constant value is usually used to correct the radar penetration for regional glacier mass balance estimation in high-mountain Asia (HMA), because little is known about the detailed distribution of radar penetration depth of the glacierized area in HMA. In this study, the penetration depth difference (hereafter referred to as PDD) of the C/X-band radar signals on glaciers over the whole HMA region was first estimated by comparing the Space Shuttle Radar Topographic Mission (SRTM) C/X-band digital elevation models (DEMs), and the spatial characteristics of the altitude-dependent PDD were analyzed on a 1° × 1° grid. The C/X-band radar PDD (the X minus C band penetration) was calculated in each 50-m elevation bin, and a linear model was used to study the correlation between the altitude and the penetration difference. The results show that the difference of the SRTM C/X-band penetration depth in the HMA region is between −1.67 p 0.65 m and 7.63 p 0.99 m, with an average value of 2.40±0.04 m. A significant linear positive correlation between elevation and the PDD was found in most of 1° × 1° grid regions in HMA. These results can be used as important reference data for estimating glacier mass balance in HMA based on SRTM DEMs.

60 Years of Glacier Elevation and Mass Changes in the Maipo River Basin, Central Andes of Chile

Glaciers in the central Andes of Chile are fundamental freshwater sources for ecosystems and communities. Overall, glaciers in this region have shown continuous recession and down-wasting, but long-term glacier mass balance studies providing precise estimates of these changes are scarce. Here, we present the first long-term (1955–2013/2015), region-specific glacier elevation and mass change estimates for the Maipo River Basin, from which the densely populated metropolitan region of Chile obtains most of its freshwater supply. We calculated glacier elevation and mass changes using historical topographic maps, Shuttle Radar Topography Mission (SRTM), TerraSAR-X add-on for Digital Elevation Measurements (TanDEM-X), and airborne Light Detection and Ranging (LiDAR) digital elevation models. The results indicated a mean regional glacier mass balance of −0.12 ± 0.06 m w.e.a−1, with a total mass loss of 2.43 ± 0.26 Gt for the Maipo River Basin between 1955–2013. The most negative glacier mass balance was the Olivares sub-basin, with a mean value of −0.29 ± 0.07 m w.e.a−1. We observed spatially heterogeneous glacier elevation and mass changes between 1955 and 2000, and more negative values between 2000 and 2013, with an acceleration in ice thinning rates starting in 2010, which coincides with the severe drought. Our results provide key information to improve glaciological and hydrological projections in a region where water resources are under pressure.

An Examination of Physical Processes That Trigger the Albedo-Feedback on Glacier Surfaces and Implications for Regional Glacier Mass Balance Across High Mountain Asia

Due to their high sensitivity to changes in climate, glaciers are one of the best natural indicators of climate change. Despite this, many underlying processes that control glacier response to climate change are poorly understood. One potentially important set of such processes are feedback mechanisms that can amplify or dampen glacier melt in response to a change in climate. Though feedbacks are recognized as important processes affecting glacier mass balances, little has been done to systematically quantify their effects. This study develops a surface energy and mass balance model to quantify the contribution of the albedo-feedback to glacier mass balance. Specifically, we quantify the roles of three trigger processes that initiate the albedo-feedback: snowpack thickness, snowfall event frequency, and heat flux supplied by precipitation. The model follows common energy balance methods but includes “switches” to turn these trigger processes off. The model is applied to Chhota Shigri Glacier using meteorological inputs from three different climate regions in High Mountain Asia (HMA). The results show that up to 80% of the average glacier melt increase from a +1°C temperature change can be attributed to the albedo-feedback. Furthermore, the system gain due to the albedo-feedback depends most on snowfall event frequency and the availability of incoming shortwave radiation during the melt season, and are thus generally largest in summer accumulation settings of HMA. This sensitivity to snowfall timing and frequency results in system gains being highest near the equilibrium line altitude, where a small change in temperature can shift precipitation phase from snow to rain. Regional analysis using climatological estimates suggests that many glaciers in the monsoonal Himalayas and southern Tibetan Plateau are likely to exhibit particularly strong albedo feedbacks. These results contribute to a growing body of literature suggesting that the mass balance of summer-accumulation type glaciers is strongly controlled by summer snowfall amount and frequency, which is closely linked with changes in air temperature. It also highlights the significance of the albedo feedback on glacier mass balance and the need to further explore feedbacks associated with glacier surface processes.

Geodetic glacier mass balance (1975–1999) in the central Pamir using the SRTM DEM and KH-9 imagery

ABSTRACTMultiple studies on regional glacier mass balance in the Pamir Mountains have been conducted using the geodetic method, but they were rarely extended to the period before 2000. In this study, we used KH-9 imagery acquired in 1975 to generate the historical DEM for the central Pamir, and then obtained the glacier elevation change by comparing this with the SRTM C-band DEM. The penetration depth of the C-band radar was corrected for different glacier surfaces, i.e. 2.96, 1.68 and 0 m for firn/snow cover, bare ice and debris-covered areas, respectively. The final results suggest that the central Pamir glaciers, overall, experienced a near-zero mass balance of −0.03 ± 0.24 m w.e. a−1 for 1975–99. Due to glacier surge activity, the elevation change patterns of individual glaciers were highly variable, and their mass balances varied from −0.12 ± 0.26 to 0.63 ± 0.20 m w.e. a−1. The mean mass budgets of the surge-type glaciers and non-surge-type glaciers were 0.03 ± 0.14 and −0.05 ± 0.28 m w.e. a−1, respectively. Concurring with previous studies, we conclude that the central Pamir glaciers may have been in a state of approximately balanced mass budget or slight mass deficit from the mid-1970s to the mid-2010s.

Comparison of Glacier Mass Balance Data in the Tien Shan and Pamir, Central Asia

ABSTRACTGlacier coverage and behavior are heterogeneous across Tien Shan and Pamir due to a climate gradient from west to east. Regional glacier mass balance data have previously been calculated using GRACE and hydrological models with differing results. In this study, in situ mass balance data of glaciers in the Tien Shan and Pamir, measured by the glaciological method between 2004 and 2012, are spatially extrapolated to the total glacier area by arithmetic averaging using (1) unfiltered balance data, and (2) a smoothing filter to the data in a way similar to that done for GRACE data. GRACE and the in situ data are the only methods that measure mass variations directly. A comparison of the extrapolated unfiltered and filtered in situ data is made with the difference between GRACE and the total water storage of the hydrological model Water Global Assessment and Prognosis Global Hydrology Model that represents glacier mass balance. The annual comparison between the extrapolated in situ and GRACE-related data does not fit very well, but the comparison of mass change rates shows quite good agreement. In comparison with GRACE-related results from the literature, the extrapolation of the unfiltered in situ glacier mass data performs best, especially in the Tien Shan.

Change in glaciers length in the Indian Himalaya: an observation and prediction under warming scenario

This study is to evaluate the state of snow and ice in Himalayan region. De-glaciation processes are enhanced by increase in the atmospheric temperature. Snow and glaciers are continuously experiencing negative mass balances across Himalayan arc. The retreat is most significant for the small and low altitude glaciers. Till 2000 the cumulative length of the glaciers in Himalaya had decreased by about 18% since 1970s. The regional glacier mass balance based on snout movement in Himalaya indicated, if present net mass balance perturbation continues the total length of glaciers would be lost by about 35% till 2020, whereas by 2050 the glaciers length would reduce by 40% from 1970s. This indicates that the present day negative mass balance requires a long time for glaciers to disappear. However, the results also indicated that the glaciers having low maximum altitude, low relief and fewer lengths are more prone to shrinkage than others in the Indian Himalaya.

Response of glacier mass balance to climate change in the Tianshan Mountains during the second half of the twentieth century

Systematic differences in glacier mass balance response to climate warming are apparent in the Tianshan Mountains, which are primarily caused by different climatic regimes and glacier hypsography. Combined mass balance data of nine monitored glaciers in the Tianshan Mountains shows that most glaciers accelerated their mass losing rate since 1970s (averaged from -24.6 mm w.e. a(-1) in 1957-1970 to -444.6 mm w.e. a(-1) in 1971-2009), but also exhibiting discrepancy and consistency during the second half of the twentieth century. To see their climatic-mass balance relationships, we employ a simple temperature index mass balance model on five well monitored glaciers in Tianshan. The model is calibrated by the observed annual, summer and winter mass balance data over the period of 1957-1980 and validated over 1981-2002. A comparison of modeled and measured annual mass balance yields an overall standard deviation of 0.465 m w.e. during the period of model runs. The calibrated mass balance model is also used to perform sensitivity experiments, which indicates the significant differences of individual glaciers in response to climate changes. This study, for the first time, tests a temperature index mass balance model on the selected observed glaciers in the Tianshan Mountains. Although there exists considerable uncertainties, we propose its potential possibility of improvement and applicability for regional glacier mass balance reconstructions and future predictions.

Influence of the Arctic Circumpolar Vortex on the Mass Balance of Canadian High Arctic Glaciers

AbstractVariability in July mean surface air temperatures from 1963 to 2003 accounted for 62% of the variance in the regional annual glacier mass balance signal for the Canadian High Arctic. A regime shift to more negative regional glacier mass balance occurred between 1986 and 1987, and is linked to a coincident shift from lower to higher mean July air temperatures. Both the interannual changes and the regime shifts in regional glacier mass balance and July air temperatures are related to variations in the position and strength of the July circumpolar vortex. In years when the July vortex is “strong” and its center is located in the Western Hemisphere, positive mass balance anomalies prevail. In contrast, highly negative mass balance anomalies occur when the July circumpolar vortex is either weak or strong without elongation over the Canadian High Arctic, and its center is located in the Eastern Hemisphere. The occurrence of westerly positioned July vortices has decreased by 40% since 1987. The associated shift to a dominantly easterly positioned July vortex was associated with an increased frequency of tropospheric ridging over the Canadian High Arctic, higher surface air temperatures, and more negative regional glacier mass balance.