Indian rivers originating in the Himalaya depend on seasonal snow-cover melt during crucial summer months. The seasonal snow cover was monitored using Advanced Wide Field Sensor (AWiFS) data of the Indian Remote Sensing Satellite (IRS) and using the Normalized Difference Snow Index (NDSI) algorithm. The investigation was carried out for a period of 3 years (2004/05, 2005/06 and 2006/07) between October and June. A total of 28 sub-basins of the Ganga and Indus river basins were monitored at intervals of 5 or 10 days. Approximately 1500 AWiFS scenes were analyzed. A combination of area–altitude distribution and snow map was used to estimate the distribution of snow cover in altitude zones for the individual basins and for the western and central Himalaya. Hypsographic curve and snow-free area was used to estimate monthly snow-line elevation. The lowest snow-line altitude in the winters of 2004/05, 2005/06 and 2006/07 was observed at 2480 ma.s.l. on 25 February 2005. In Ravi basin for the year 2004/05, snow accumulation and ablation were continuous processes throughout the winter. Even in the middle of winter, the snow area was reduced from 90% to 55%. Similar trends were observed for 2005/06 and 2007/08. In Bhaga basin, snowmelt was observed in the early part of the winter, i.e. in December, and no significant melting was observed between January and April.

This paper presents a method for deriving the snowline altitude using a combined analysis of terrain elevation and multispectral Advanced Wide Field Sensor (AWiFS) data from the RESOURCESAT-1 satellite, launched by India on 17 October 2003. AWiFS is a unique instrument capable of acquiring imagery of the world repeatedly every 5 days with very high radiometric resolution. It provides a wide swath width, which is very useful for snow-cover mapping. Snowline altitude is a good indicator of snow coverage. Snowline altitude for the period from October 2004 to June 2005, and from October 2006 to June 2007, is determined for the Baspa Basin, which is located in the Kinnaur district of Himachal Pradesh, India. It is observed that snowline altitude is generally higher during the year 2006/07 than during 2004/05, except in December 2006 and March 2007. The results obtained with the analysis presented here are validated using available meteorological data and are found to be satisfactory. This thus establishes a method that can be applied to other terrains and over longer periods of time within the coverage of the AWiFS sensor data.

The history of glacier length fluctuations serves as a reliable indicator of the past climate. In this paper, a numerical flowline model has been used to study the relationship between length variations of Chhota Shigri glacier and local climate since 1876. The simulated front positions of Chhota Shigri glacier are in agreement with those observed. After a successful simulation of the past retreat, the model was also used to predict future evolution of the glacier for the next 100 years under different climatic scenarios. These simulations indicate that the Chhota Shigri glacier may lose ~90% of its present volume by 2100 if the local temperature increases by 2.4 K, and for a temperature rise of 5.5 K, the glacier loses almost all its volume.

An 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−1 and 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.

We investigated area changes in glaciers covering an area of ∼200 km2 in the Tista basin, Sikkim, Eastern Indian Himalaya, between ∼1990 and 2010 using Landsat Thematic Mapper (TM) and Indian Remote-sensing Satellite (IRS) images and related the changes to debris cover, supraglacial lakes and moraine-dam lakes. The glaciers lost an area of 3.3 ± 0.8% between 1989/90 and 2010. More detailed analysis revealed an area loss of 2.00 ± 0.82, 2.56 ± 0.61 and 2.28 ± 2.01 km2 for the periods 1989–97, 1997–2004/05 and 2004–2009/10, respectively. This indicates an accelerated retreat of glaciers after 1997. On further analysis, we observed (1) the formation and expansion of supraglacial lakes on many debris-covered glaciers and (2) the merging of these lakes over time, leading to the development of large moraine-dam lakes. We also observed that debris-covered glaciers with lakes lose a greater area than debris-covered glaciers without lakes and debris-free glaciers. The climatic data for 24 years (1987–2011), measured at the Gangtok meteorological station (1812 m a.s.l.), showed that the region experienced a 1.0°C rise in the summer minimum temperature and a 2.0°C rise in the winter minimum temperature, indicating hotter summers and warmer winters. There was no significant trend in the total annual precipitation. We find that glacier retreat is caused mainly by a temperature increase and that debris-covered glaciers can retreat at a faster rate than debris-free glaciers, if associated with lakes.

Despite the important role of supraglacial debris in ablation, knowledge of debris thickness on Himalayan glaciers is sparse. A recently developed method based on reanalysis data and thermal band satellite imagery has proved to be potentially suitable for debris thickness estimation without the need for detailed field data. In this study, we further develop the method and discuss possibilities and limitations arising from its application to a glacier in the Himalaya with scarce in situ data. Surface temperature patterns are consistent for 13 scenes of Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) and Landsat 7 imagery and correlate well with incoming shortwave radiation and air temperature. We use an energy-balance approach to subtract these radiation or air temperature effects, in order to estimate debris thickness patterns as a function of surface temperature. Both incoming shortwave and longwave radiation are estimated with reasonable accuracy when applying parameterizations and reanalysis data. However, the model likely underestimates debris thickness, probably due to incorrect representation of vertical debris temperature profiles, the rate of heat storage and turbulent sensible heat flux. Moreover, the uncertainty of the result was found to increase significantly with thicker debris, a promising result since ablation is enhanced by thin debris of 1–2 cm.

We estimate the distribution of ice thickness for a Himalayan glacier using surface velocities, slope and the ice flow law. Surface velocities over Gangotri Glacier were estimated using sub-pixel correlation of Landsat TM and ETM+ imagery. Velocities range from ˜14–85 m a–1 in the accumulation region to ˜20–30 m a–1 near the snout. Depth profiles were calculated using the equation of laminar flow. Thickness varies from ˜540 m in the upper reaches to ˜50–60 m near the snout. The volume of the glacier is estimated to be 23.2 ± 4.2 km3.

The accumulation area ratio (AAR) for Himalayan glaciers representing zero mass balance is substantially lower than for North America and Europe. Regression analysis suggests 0.44 for the AAR representing zero mass balance in the western Himalaya. A good correlation was observed when this method was applied to individual glaciers such as Gara and Gor-Garang in Himachal Pradesh, India. The correlation coefficients (r), using 6 and 7 years of data, respectively, were 0.88 and 0.96 for Gara and Gor-Garang Glaciers, respectively. However, when data from six western Himalayan glaciers were correlated, the correlation was 0.74. The AAR was also estimated by using Landsat images which can be useful in obtaining a trend in mass balance for a large number of Himalayan glaciers for which very little information exists.

A higher correlation was observed between equilibrium-line altitude (ELA) and mass balance. The field data from Gara and Gor-Garang Glaciers shows a high correlation coefficient, i.e. −0.92 and −0.94, respectively. The ELA values obtained from the Landsat satellite images combined with topographic maps suggest positive mass balance for the year 1986–87 and negative for 1987–88.

Radio-echo sounding techniques are very useful for fast profiling of seasonal snowpack. Ground-penetrating radar (GPR) is used widely for various cryospheric applications, such as snow/glacier depth estimation, snow layer identification and snow water equivalent assessment. The dielectric constant of snow is an important input parameter for the acquisition and interpretation of GPR data from the snowpack. In this study, snow dielectric constant was measured along with physical properties of snow using a snow fork operating at 1 GHz frequency. Experiments were conducted at field observatories of the Snow and Avalanche Study Establishment located in different Himalayan ranges: Patseo (Greater Himalayan range), Dhundhi and Solang (Pir Panjal range). Interseasonal spatial and temporal variations in snow dielectric constant and associated snowpack properties were analysed for five winter seasons (2010-14). The mean seasonal snow dielectric constant is higher at Dhundhi (1.82 ±0.02) than at Patseo (1.69 ±0.02). The measured snow dielectric constant was used to derive snow density and liquid-water content (LWC). A better correlation between snow dielectric constant and LWC is observed for high-density snow (>300kgm-3; R2 = 0.95) than for low-density snow (<200kgm-3; R2 = 0.73). Snow-fork-derived snow density was in good agreement with manually measured values. The snow dielectric constant database generated during this study can be used as a reference for various field applications of GPR in snow-related studies.

The collapse of South Asia's Gyps vulture populations is attributable to the veterinary use of the non-steroidal anti-inflammatory drug (NSAID) diclofenac. Vultures died after feeding on carcasses of recently-medicated animals. The governments of India, Nepal and Pakistan banned the veterinary use of diclofenac in 2006. We analysed results of 62 necropsies and 48 NSAID assays of liver and/or kidney for vultures of five species found dead in India between 2000 and 2012. Visceral gout and diclofenac were detected in vultures from nine states and three species: Gyps bengalensis, Gyps indicus and Gyps himalayensis. Visceral gout was found in every vulture carcass in which a measurable level of diclofenac was detected. Meloxicam, an NSAID of low toxicity to vultures, was found in two vultures and nimesulide in five vultures. Nimesulide at elevated tissue concentrations was associated with visceral gout in four of these cases, always without diclofenac, suggesting that nimesulide may have similar toxic effects to those of diclofenac. Residues of meloxicam on its own were never associated with visceral gout. The proportion of Gyps vultures found dead in the wild in India with measurable levels of diclofenac in their tissues showed a modest and non-significant decline since the ban on the veterinary use of diclofenac. The prevalence of visceral gout declined less, probably because some cases of visceral gout from 2008 onwards were associated with nimesulide rather than diclofenac. Veterinary use of nimesulide is a potential threat to the recovery of vulture populations.

In the present study we examined the immune-enhancing effect of a nucleoside-nucleotide mixture on the non-specific T-cell immune functions of senescence-accelerated mice (SAM) fed on a low-protein diet. The immune functions studied were in vitro thymic and splenic cell lymphoproliferative responses to phytohaemagglutinin, lipopolysaccharide and concanavalin A and their production of interleukin-2 (IL-2) and interferon-γ (INF-γ) in response to mitogen stimulation. SAMP8 mice aged 3 and 6 months were used. In each age group, mice were fed on diets containing either 50g casein/kg, 50 g casein/kg supplemented with 5 g nucleoside-nucleotide mixture/kg or 200 g casein/kg for 3 weeks. The supplemented 3- and 6-month-old mice had higher (P<O·O5) thymic and splenic cell counts compared with the low-protein group. In both age groups of mice, concanavalin A induced higher (P<0·05) total thymic and splenic lymphoproliferative responses for the nucleoside-nucleotide mixture-supplemented group compared with the 50 g casein/kg dietary groups. Thymic and splenic production of IL-2 was higher for the 3-month-old mice in both the supplemented and the 200 g casein/kg dietary groups. INF-γ production in the supplemented 3-month-old group and the 6-month-old 200 g casein/kg dietary group was higher (P<0·05) compared with the other groups. Overall the supplemented 3-month-old mice exhibited both higher lymphoproliferative responses and production of cytokines compared with the supplemented 6-month-old mice. The results indicate that early nucleoside-nucleotide mixture supplementation may enhance the immune response in protein-deprived SAMP8 mice