Glacio-archaeological evidence of permanent settlements within a glacier end moraine complex during 980-1840 AD: The Miyar Basin, Lahaul Himalaya, India

This study presents glacio-archaeological evidence from the Miyar basin, Lahaul Himalaya, that points towards the former presence of a well settled agricultural society, within a glacier end moraine complex. Three high altitude villages (Tharang, Phundang and Patam, now in ruins) with elaborate irrigation networks thrived within the end moraine complex of Tharang glacier at 3700 m a.s.l. Evidence exists in the form of dilapidated houses which had an organised internal space, chronologically constrained by radiocarbon (14C) dating. These settlements occupied the end moraine complex between 980 and 1840 CE, thereby encompassing the majority of Little Ice Age period (1300–1600 CE), as defined elsewhere. The existence of settlements along with an irrigation system and associate fields at ∼3700-3800 m a.s.l. for almost ∼860 years during the late 10th to early 19th centuries suggests more favourable climatic (warm) conditions that at present. By contrast, present habitation is restricted to areas below ∼3500 m a.s.l. However, the slope controlled irrigation system also suggests moisture stressed conditions during the 980–1840 CE period, similar to present. The available temperature and snowfall proxies for the region support our proposed timing, and suggest favourable climatic conditions for the survival of these settlements

Frontal changes in medium-sized glaciers in Sikkim, India during 1988–2018: Insights for glacier-climate synthesis over the Himalaya

Summary: The study assesses terminus retreat of medium-sized glaciers (1988–2018) using geospatial dataset and field study in Sikkim which is under the direct influence of the Indian SW monsoon. It also explores the causes of intra-regional and inter-regional diverse patterns of glacier retreat under the purview of topographical and climatic factors to develop a glacier-climate synthesis over the region. Glaciers have retreated in a range from 63.9 to 3.9 m yr−1 and lost a total area of ∼2.53% (0.08% yr−1) in the study area. The intra-regional heterogeneity in glaciers retreat seems to be caused by topographical factors in the study area. A comparison of glacier retreats with other parts of the Himalayas reveals a declining gradient from the northwest to the eastern Himalayas, broadly. This inter-regional disparity in the retreat rate seems to be caused by existing climatic regimes over different parts of the Himalayas. The results help to comprehend the glacier-climate synthesis over the Himalayan region

Glacier Dynamics in Changme Khangpu Basin, Sikkim Himalaya, India, between 1975 and 2016

This study provides a high resolution glacier database in the Changme Khangpu Basin (CKB) using LANDSAT 8 (2014) and Sentinel-2A image (2016), mapping of 81 glaciers that cover a 75.78 ± 1.54 km2 area. Composite maps of land surface temperature, slope and Normalized differential Snow Index have been successfully utilized in delineating near accurate debris cover boundary of glaciers. The cumulative controlling parameters of aspect, elevation, slope, and debris cover have been assessed to evaluate the nature of glacier distribution and dynamics. The local topographic settings seem to have significantly determined the glacier distribution in the CKB. Almost 20% area erstwhile under glacier cover has been lost since 1975 at an average rate of −0.453 ± 0.001 km2a−1. The recent decade (2001–2016) has witnessed a higher rate of area shrinkage (−0.665 ± 0.243 km2a−1), compared to a relatively lower rate of recession (−0.170 ± 0.536 km2a−1) between 1988 and 2001. The lower rates of glacial recession can most likely be induced regionally due to relatively cooler decadal late summer temperatures and peak in the monsoon spell. Glaciers with western and north-western aspects showed more vulnerability to area loss than the rest of the aspects. Lower altitude glaciers have receded faster than ones perched up on higher elevations. The rate of glacier area recession has been nearly twice that on clean glaciers as compared to debris-covered glaciers in the CKB

Spatially heterogeneous glacier elevation change in the Jankar Chhu Watershed, Lahaul Himalaya, India derived using ASTER DEMs

This study investigates elevation change (dh) and geodetic mass budget of glaciers in the Jankar Chhu Watershed (JCW), Lahaul Himalaya, India, based on the difference in ASTER DEMs during 2002–2018. Glacier-wide spatially heterogeneous dh patterns were evaluated in the context of morphological and topographical settings. During 2002–2018, glaciers show a mean annual elevation change rate (dh/dt) of −0.38 ± 0.10 m a−1, resulting in a specific mass budget of −0.32 ± 0.09 m w.e.a−1, close to the previously reported estimates in western Himalaya. Nearly stagnant thick debris-covered tongue (>10% debris cover) characterized by melt hotspots exhibits maximum dh at up-glacier instead of the terminus. Debris-free glaciers (<10% debris cover) show maximum dh near the terminus. Spatially heterogeneous dh under varying debris cover is interpreted as an insulating effect of debris thickness as validated by field measurements. We suggest that elevation change of debris-covered glaciers cannot be generalized and glacier-wide spatially detailed mapping of dh is necessary to better understand the control of different surface morphology under warming climatic conditions in the western Himalayas

Flow velocities of the debris-covered Miyar Glacier, western Himalaya, India

Spatiotemporal surface velocity measurements of the alpine valley type debris-covered Miyar Glacier of the Chandrabhaga (Chenab) basin, western Himalaya, were assessed based on the cross-correlation of Landsat images spanning nearly three decades (1992-2019). Long-term (1950-2015) temperature and precipitation trends were evaluated using Asian Precipitation Highly Resolved Observational Data Integration Towards Evaluation (APHRODITE) datasets. The mean velocity (1992-2019) of the Miyar Glacier is ∼29 m/yr, with spatial patterns revealing that the debris-covered tongue is nearly stagnant (∼5 m/yr) compared to the debris-free up-glacier zone (∼35 m/yr). The transition zone from clean to debris-covered ice in the mid-ablation area shows the highest long-term mean velocities of ∼60 m/yr during the observation period, likely resulting from a steep surface gradient and greater ice thickness than the other regions of this glacier. The slow-moving and nearly stagnant debris-covered area reveals the highest amount of surface lowering due to the expansion of supraglacial ponds. Miyar Glacier experiences summer speed-up of ∼67–80% in seasonal velocity compared to winter, interpreted as a result from enhanced basal sliding during summer months due to warmer temperatures inputting more meltwater into the subsurface drainage system. Inter-annual velocity variations are greatest in the upper glacier, with higher velocities observed more frequently in recent decades. Future work should aim to elucidate the causes of this pattern, considering the overall rising air temperature trend in the western Himalaya

Landslide susceptibility mapping using maximum entropy and support vector machine models along the highway corridor, Garhwal Himalaya

The main objective of this study to produce landslide susceptibility zones using maximum entropy (MaxEnt) and support vector machine (SVM) data-driven models along the Tipari to Ghuttu highway corridors in the Garhwal Himalaya. A landslide inventory has been prepared through field surveys and LISS-IV and Landsat 8 satellite images. The datasets of 85 landslides were categorised into training and test sets. In this study 11 landslide conditioning variables were used that are; altitude, slope angle, aspect, plan curvature, topographic wetness index, normalised difference vegetation index (NDVI), land use, soil texture, distance to rivers, distance to faults, and distance to the road. The result produced using MaxEnt and SVM model were subsequently validated using receiver operating characteristics curve (ROC) with test sets of landslide dataset. Both the models have good prediction capabilities. MaxEnt has ROC value of 0.78 while SVM has the highest prediction rate of 0.85

Potential glacial lake outburst flood assessment in a changing environment, Chhombo Chhu Watershed, Sikkim Himalaya, India

The Chhombo Chhu Watershed of Tista basin in Sikkim Himalaya, located between the Greater Himalayan range and the Tethyan Sedimentary Sequence, is the storehouse of number of glacial lakes with large areas and volumes. In this study, we mapped the glacial lakes changes between 1975–2018 and assessed its dynamics based on manual analysis of optical satellite images using KeyHole-9 Hexagon (∼4 m), Landsat Series (∼15–30 m), and Sentinel 2 A-MSI (∼10–20 m) imagery and verified during field surveys. The results show that the number of lakes has increased from 62 to 98, and its total area expanded significantly by ∼34.6 ± 5.4%, i.e. from 8.5 ± 0.2 km2 in 1975 to 11.4 ± 0.6 km2 by 2018, at an expansion rate of 0.8 ± 0.1% a−1. Lake outburst susceptibility result reveals that a total of twenty-seven potentially dangerous glacial lakes exist in the watershed; 5 have a status of ‘high’ outburst probability, 17 ‘medium’ and 5 ‘low’. The majority of the proglacial lakes in the watershed have significantly enlarged due to the faster melting and calving processes as a result of accelerating increasing long-term average annual trend of temperature (+0.283° Ca−1; 95% confidence level) and homogeneous or slightly declining precipitation

Late Holocene Glacier Dynamics in the Miyar Basin, Lahaul Himalaya, India

Detailed field mapping of glacial and paraglacial landforms and optical dating from these landforms are used to reconstruct the early Holocene glaciation in the semi-arid region of Miyar basin, Lahaul Himalaya. The study identifies three stages of glaciation, of decreasing magnitude and termed, from oldest to youngest, the Miyar stage (MR-I), Khanjar stage (KH-II), and Menthosa advance (M-III). The oldest glacial stage (MR-I) has been established on the basis of detailed geomorphological evidence such as U-shaped valley morphology, trimlines, and truncated spurs. It is speculated to be older than the global Last Glacial Maximum (gLGM) based on the magnitude of ΔELA (Equilibrium-Line Altitude, 606m). No evidence of glacier expansion recorded from the basin correlates with the period of the gLGM. The second stage (KH-II) is well represented by extensive depositional features such as lateral and terminal moraines, drumlins, and lacustrine fills that have been constrained within 10 ± 1 to 6.6 ± 1.0 ka (Optically stimulated luminescence—OSL—ages), dating it to the early Holocene advance following the Younger Dryas cooling event. Exceptionally young glacial records of expansion are limited within a few hundred meters of the present termini of tributary glaciers and correlates with the 18th-century cooling event. Records of this glacial advance, termed the Menthosa advance, are clearly noticed in some tributary valleys