D. P. Dobhal

Influence of debris cover and altitude on glacier surface melting: a case study on Dokriani Glacier, central Himalaya, India

Abstract Most of the central Himalayan glaciers have surface debris layers of variable thickness, which greatly affect the ablation rate. An attempt has been made to relate debris-cover thickness to glacier surface melting. Thirty stakes were used to calculate ablation for debris-covered and clean ice of Dokriani Glacier (7 km2) from 2009/10 to 2012/13. Our study revealed significant altitude-wise difference in the rate of clean and debris-covered ice melting. We found a high correlation (R 2 = 0.92) between mean annual clean-ice ablation and altitude, and a very low correlation (R 2 = 0.14) between debris-covered ice melting and altitude. Debris-covered ice ablation varies with variation in debris thickness from 1 to 40 cm; ablation was maximum under debris thicknesses of 1–6 cm and minimum under 40 cm. Even a small debris-cover thickness (1–2 cm) reduces ice melting as compared to that of clean ice on an annual basis. Overall, debris-covered ice ablation during the study period was observed to be 37% less than clean-ice ablation. Strong downwasting was also observed in the Dokriani Glacier ablation area, with average annual ablation of 1.82 m w.e. a–1 in a similar period. Our study suggests that a thinning glacier rapidly becomes debris-covered over the ablation area, reducing the rate of ice loss.

Change of Tipra Glacier in the Garhwal Himalaya, India, between 1962 and 2008:

Systematic observations of Himalayan glaciers over the last few decades provide reliable indications of continuous shrinkage of most of the glaciers. Changes in mass, volume, area and length of glaciers are reported, but an up-to-date regional assessment of glacier changes is lacking. In the present study, satellite data, maps and ground-based measurements have been used to obtain the snout retreat and surface changes of the Tipra Glacier in the Alaknanda river basin of the Garhwal Himalaya for the period 1962–2008. The study reveals that a large part of the glacier has been detached from the main trunk and separated into the Tipra (7.5 km2) and Rataban (7.4 km2) Glaciers as it had one outlet (snout) in 1987. Between 1962 and 2002 estimated surface area reduced by ~18% and snout retreat was ~535 m with an average rate of 13.4 m a−1. Measurement of snout positions of the Tipra and Rataban Glaciers from 2002 to 2008 indicates an enhanced annual retreat of 21.3 and 21.2 m a−1, respectively. Total frontal area vacated during this period was calculated to be 0.084 km2 for Tipra Glacier and 0.028 km2 for Rataban Glacier. The estimated Equilibrium Line Altitude (ELA) rise was 76 m for the Tipra Glacier and 57 m for the Rataban Glacier. Accumulation Area Ratio (AAR) was calculated as 0.47 for the Tipra Glacier and 0.49 for the Rataban Glacier, during the study period. The observations compared with the other studies carried out in the region show a significant reduction in glacier areas. The increased retreat rate of glacier snouts is probably a direct consequence of global warming. The present snouts of the Tipra and Rataban Glaciers are located at altitudes of 3865 and 4120 m, respectively.

Four decades of glacier mass balance observations in the Indian Himalaya

Understanding the glacier mass balance is necessary to explain the rate of shrinkage and to infer the impact of climate change. The present study provides an overview of the glacier mass balance records by glaciological, geodetic, hydrological and accumulation-area ratio (AAR) and specific mass balance relationship methods in the Indian Himalaya since 1970s. It suggests that the mass balance measurements by glaciological methods have been conducted for ten glaciers in the western Himalaya, four glaciers in the central Himalaya and one in the eastern Himalaya. Hydrological mass balance has been conducted only on Siachen Glacier from 1987 to 1991. Geodetic method has been attempted for the Lahaul–Spiti region for a short time span during 1999–2011 and Hindu Kush–Karakoram–Himalaya region from 2003 to 2008. We compared in situ specific balance data series with specific mass balance derived from AAR and specific mass balance relationship. The results derived from existing and newly presented regression model based on AAR and specific mass balance relationship induced unrealistic specific mass balance for several glaciers. We also revised AAR0 and ELA0 based on available in situ AAR and specific mass balance data series of Indian Himalayan glaciers. In general, in situ specific and cumulative specific mass balance observed over different regions of the Indian Himalayan glaciers shows mostly negative mass balance years with a few positive ones during 1974–2012. On a regional level, the geodetic studies suggest that on the whole western, the central and the eastern Himalaya experienced vast thinning during the last decade (2000s). Conversely, Karakoram region showed slight mass gain during almost similar period. However, the glaciological, hydrological and geodetic mass balance data appear to exhibit short time series bias. We therefore recommend creation of benchmark glaciers network for future research to determine the impact of climate change on the Himalayan cryosphere.

Assessment of snowmelt runoff modelling and isotope analysis: a case study from the western Himalaya, India

Abstract The major river systems of India, i.e. the Indus, Ganga and Brahmaputra river systems originating in the Himalayan region, are considered the lifeline of the Indian subcontinent. The main sources maintaining the flow of the Himalayan rivers are snow/glacial melt runoff, rainfall runoff and base flow. The Beas River originates from Beas Kund Glacier in the Himalayan region and flows down to join the Sutlej River, which is a tributary of the Indus River system. In the present study two approaches, namely hydrologic modelling and isotope analysis, have been applied to estimate the contribution of snow and glacier melt. Samples of streamflow, rainfall and snow for isotopic analysis were collected daily from April to September and weekly from October to March during 2010 and 2011. The isotope analysis of samples reveals that the snow/glacier melt contribution to the Beas River at Manali is 50% of the total flow during these 2 years. Snowmelt runoff modelling has been carried out using the SNOWMOD model, and the snow/glacier melt runoff contribution is calculated to be 52% of the total flow during the same period. These findings indicate that the results obtained from the two approaches are similar.

Late Quaternary glacial advances in the Tons River Valley, Garhwal Himalaya, India and regional synchronicity

The glacial history of the Tons River Valley reveals significant changes in the glacier extent during the late Quaternary driven by regional and global climatic changes. The successions of moraines in glaciated valley of the upper Tons River, Garhwal Himalaya, provide evidence of at least five glacial advances during the late Quaternary Period. This study discusses about the synchronicity of Himalayan glaciers and comparison between results of Optically Stimulated Luminescence (OSL) and Cosmogenic Radio Nuclide (CRN 10Be) dates. The OSL dates of moraine sediments deposited by glacier in the upper Tons valley show parallelism with the ages deduced from the CRN of 10Be by Scherler et al. in the same area. The five episodes of glacier advances are dated at 20 ± 3, 16 ± 2, 8 ± 1.2, 6 ± 0.7 and 3 ± 0.6 kyr (between Marine Isotope Stages (MISs) I and II). Two of the more extensive phases of glaciation were during the early and later parts of MIS II, which attributed to the lower temperature and enhanced the mid-latitude westerlies. During the periods between 20 ± 3 kyr and present day, the glacier lost ~47 km2 (33%) area, 0.88 × 1010 m3 water equivalent (w.e.) volume with the rate of 0.44 × 106 m3 w.e./yr, which is close to the current melting rates of Central Himalayan glaciers. The estimation of equilibrium line altitude (ELA) using these dates and geomorphic data suggests a vertical shift of ~451 m for Jaundhar Glacier and ~598 m for Bandarpunch Glacier since 20 kyr. The results from Tons valley glaciation show synchronicity with the records of glacial advancements from the other Himalayan glacier valleys. These data allow testing of two widely used dating techniques and importance of global climate change and monsoon influence on glaciation in the Himalaya.

Glacier changes in Upper Tons River basin, Garhwal Himalaya, Uttarakhand, India

We estimate the spatial changes in the Jaundhar, Jhajju and Tilku glaciers in the Tons River basin (Garhwal Himalaya) between 1962 and 2010 using Landsat Satellite data, topographic maps along with field surveys. We estimate the overall shrinking in the area of the glaciers to be ~ 3.6 km2 (5.4% of total area) and ~ 1,709 m, ~ 800 m and ~ 700 m of frontal retreat (snout) with an average of 34.18, 15.38 and 13.46 m a–1 for the Jaundhar, Tilku and Jhajju Glaciers respectively. However, frontal retreat rates are not uniform in all glaciers even under the same climatic domain. The Jaundhar Glacier (55 km2) has been separated into two parts; North Jaundhar (40 km2) and South Jaundhar (15 km2) between 1975 and 1990. Study on these fragmented glaciers shows a continuous and unusual retreat of glaciers after 1990. Compared with the regional mean of glaciers retreat in the Uttarakhand Himalaya, the glaciers show heterogeneous retreat rates. This uncertainty may possibly be due to size, surface morphology and gradient of the individual glaciers and can be attributed to degeneration and rapid melting on the glaciers. Meteorological data available from this region show increasing summer temperature and less winter precipitation in last few decades. Further more studies on these glaciers will shed light on several factors influencing changes and retreat on the Himalayan glacier systems.

Variable Response of Glaciers to Climate Change in Uttarakhand Himalaya, India

The glaciers are fragile and dynamic in nature and influence the climate system (e.g. albedo feedback) and as well as key indicator of climate change. The reduction in mass, volume, area and length of glaciers are considered as clear signals of a warmer climate. Uttarakhand Himalaya contains 968 glaciers out of the total 9,575 glaciers in Indian part of the Himalaya, covering an area of 2,888.37 km2 with 213.74 km3 of ice volume lies between the altitudes 6,600 and 3,860 m with different dimensions. The observations made during the end of nineteenth century over the Uttarakhand Himalayan glaciers indicate that there is continuous retreat of glaciers but rate of retreat are different to different glaciers. In this study, the results of a detailed mapping campaign and ground-based measurements of terminus retreat, area vacated and mass/volume change has been carried out on few glaciers for the period between 1962 and 2010. The study shows continuous negative mass balance on Tipra , Dunagiri , Dokriani and Chorabari glaciers during last three decades. In general, Uttarakhand Himalayan glaciers are under substantial thinning (Mass loss) and reduction of length and area in the present climate conditions.

Extended T-index models for glacier surface melting: a case study from Chorabari Glacier, Central Himalaya, India

Two enhanced temperature-index (T-index) models are proposed by incorporating meteorological parameters viz. relative humidity, wind speed and net radiation. The models are an attempt to explore different climatic variables other than temperature affecting glacier surface melting. Weather data were recorded at Chorabari Glacier using an automatic weather station during the summers of 2010 (July 10 to September 10) and 2012 (June 10 to October 25). The modelled surface melt is validated against the measured point surface melting at the snout. Performance of the developed models is evaluated by comparing with basic temperature-index model and is quantified through different efficiency criteria. The results suggest that proposed models yield considerable improvement in surface melt simulation. Consequently, the study reveals that glacier surface melt depends not only on temperature but also on weather parameters viz. relative humidity, wind speed and net radiation play a significant role in glacier surface melting. This approach provides a major improvement on basic temperature-index method and offers an alternative to energy balance model.

Correction to: Spatio-temporal variability of near-surface air temperature in the Dokriani glacier catchment (DGC), central Himalaya

The original version of this article unfortunately contained a mistake. Figures 4 and 5 captions were interchanged. The correct captions are given below.

Surface Energy and Mass Balance on the Ablation Zone of Chorabari Glacier, Central Himalaya, India

The energy balance at the glacier-atmosphere interface is the key control of the interaction between glaciers and climate. Melting at the glacier surface is controlled by the surface energy balance. Here we report, the energy and mass balance study carried out on Chorabari Glacier, Mandakini basin, Central Himalaya for the period of one year (Nov 2011-Oct 2012). The meteorological data collected from an Automatic Weather Station (AWS) were used to compute the annual cycle of local surface energy balance in the ablation zone. The average energy flux is calculated 28.5 Wm-2 for surface melting. In addition, the net radiation component is the largest contributor (52%) to the total surface energy heat flux followed by turbulent sensible (26%) and latent (9%) fluxes and the remaining 13% is only from subsurface heat. The study shows that the modelled ablation is well matched with ground measurement by 2% relative error.