The concerns over the depletion of the Himalayan cryosphere have attracted the attention of scientists, decision makers, and policymakers the world over to understand the factors driving glacier recession. Direct measurements of glacier mass balance over the Indian Himalaya are available on a limited number of glaciers and mostly come from the period 1975-90. In order to observe the current status of the western Himalayan glaciers we selected eight benchmark glaciers from North western Himalayas for detailed in situ mass balance measurement (03 in the Kashmir Himalayas and 05 in the Zanaskar Himalayas). The glaciological mass balance observations obtained from all these glaciers revealed that there is a continuous surface mass loss as well as recession during the last seven years. However, the rate of mass loss varies among these glaciers. For example, the Kolahoi, Hoksar, Wakhalbal and Machoi are showing an annual mass balance of -0.84, - 0.96, -0.82 and -0.98 m.we a⁻¹ respectively. Further, the ablation measurements obtained from the Lilong, Kangrez, Pansila and Drung Drung showed an annual mass loss of -0.65, -0.81, -0.58 and -0.77 m.we a⁻¹ respectively. To understand the recent glacier dynamics, we estimated decadal glacier thickness changes over the entire Jammu, Kashmir and Ladakh using TanDEM-X and SRTM- C DEMs from 2000 to 2012. The study area is often divided in six mountain ranges: Pir Panjal range, (PPR), Greater Himalaya range (GHR), Shamaswari range, Zanaskar range, Ladakh range and Karakoram range(KKR), each with distinct climatic and topographic characteristics. More than 12,000 glaciers having 19,727 ±054 sq km area were investigated and it was found that the glaciers have thinned on an average −0.35 ±0.33 m a⁻¹ during the period. The highest thinning of − 1.69 ± 0.60 m a⁻¹ was observed in the PPR while as a marginal glacier thinning of − 0.11 ± 0.32 m a⁻¹ was observed in the KKR. The observed glacier thickness changes indicated a strong influence of topographic parameters. Higher glacier thickness reduction was observed at lower altitudes (− 1.40 ± 0.53 m a⁻¹ ) and with shallower slopes (− 1.52 ± 0.40 ma⁻¹ ). Significantly higher negative glacier thickness changes were observed on the south slopes (− 0.55 ± 0.37 m a⁻¹ ). The thickness loss was higher on the debris-covered glaciers (− 0.50 ± 0.38 m a⁻¹ ) than the clean glaciers (− 0.32 ± 0.33 m a⁻¹ ). There are only a few global and regional ice thickness datasets, and field measurements are even more limited, particularly in the Himalaya. In this research, we simulated the ice reserves in the Kashmir and Ladakh sub-basins of the UIB using a spatially distributed ice thickness model (GlabTop). The simulated ice thickness estimates of the glaciers situated in the Kashmir and Ladakh regions respectively, were validated using GPR measurements. Overall, the GlabTop model accurately simulates glacier ice thickness and its spatial patterns from almost all the transects on the two glaciers, even though the model somewhat underestimates ice thickness by 9.5 per cent. Knowledge of glacier thickness and volume is crucial for a wide range of applications, including predicting future water availability, assessing glacier hazards, conducting glacio-hydrological investigations, estimating future sea-level rise and predicting future status and evolution of glaciers, that are rapidly melting due to climate change. There are ~5600 glaciers covering ~17950 sq km in the Karakoram and based on 20 year remote sensing data (2000-2020), glacier area change (-0.96 per cent) analysis showed that the glaciers are either retreating (3621), stable (1766), or even advancing (215), indicating an average recession of -4.64 per cent, -.08 per cent and 1.17 per cent respectively with variation between east and west Karakoram. The analysis showed a significant influence of topography on the observed glacier changes indicated by higher altitudes and northerly aspects of the advancing and stable glaciers; and lower altitudes and southerly aspects of the retreating glaciers.
