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Snout monitoring of the Gangotri glacier (Uttarakhand, India) during the ablation season (May to September) in years 2005 and 2015 by using rapid static and kinematic GPS survey reveals that the retreating rate has been comparatively more declined than shown by the earlier studies. Our study is based on the individual measurement by the remote sensing, added by the ground observations by using Differential global positioning system (DGPS) to determine the precise recession rate of the glacier at sub-centimeter level of accuracy. The GPS dataset show that the total average retreat along the snout has been 102.57 ± 0.05 m from 2005 to 2015 with an average rate as 10.26 ± 0.05 m/yr. Additionally, the shift in snout position was also measured through multi-temporal satellite data from 1989 to 2016. The results indicate that the Gangotri glacier snout has retreated by 585.62 ± 38.30 m during this period with an average retreat of 26.75 ± 4.36 m/yr from 1989 to 1999, 21.58 ± 3.77 m/yr from 1999 to 2009 and 14.60 ± 4.81 m/yr from 2009 to 2016. Such a decline in retreat is further confirmed by the satellite data set. A close examination of meltwater discharge and retreating rate (r2 = 0.95) show that both parameters are strongly correlated. Therefore, we suggest that a consistent decrease in meltwater discharge from 1999 to 2015 is in agreement with decreasing trend of retreating rate during the recent years. To determine the possible causes of decreased retreating rate, a relationship between debris thickness and melt rate was also established by ablation stakes. Further, we infer that the declining trend in the glacier retreat is not only controlled by prevailing weather conditions (rainfall and air temperature) but is also governed by increased debris cover on the glacier surface which prevents the ice to melt. [ABSTRACT FROM AUTHOR]

We present new insights on the time-averaged surface velocities, convergence and extension rates along arc-normal transects in Kumaon, Garhwal and Kashmir-Himachal regions in the Indian Himalaya from 13 years of high-precision Global Positioning System (GPS) time series (1995-2008) derived from GPS data at 14 GPS permanent and 42 campaign stations between $$29.5{-}35^{\circ }\hbox {N}$$ and $$76{-}81^{\circ }\hbox {E}$$ . The GPS surface horizontal velocities vary significantly from the Higher to Lesser Himalaya and are of the order of 30 to 48 mm/year NE in ITRF 2005 reference frame, and 17 to 2 mm/year SW in an India fixed reference frame indicating that this region is accommodating less than 2 cm/year of the India-Eurasia plate motion ( $${\sim }4~\hbox {cm/year}$$ ). The total arc-normal shortening varies between $${\sim }10{-}14~\hbox {mm/year}$$ along the different transects of the northwest Himalayan wedge, between the Indo-Tsangpo suture to the north and the Indo-Gangetic foreland to the south indicating high strain accumulation in the Himalayan wedge. This convergence is being accommodated differentially along the arc-normal transects; $${\sim } 5{-}10~\hbox {mm/year}$$ in Lesser Himalaya and 3-4 mm/year in Higher Himalaya south of South Tibetan Detachment. Most of the convergence in the Lesser Himalaya of Garhwal and Kumaon is being accommodated just south of the Main Central Thrust fault trace, indicating high strain accumulation in this region which is also consistent with the high seismic activity in this region. In addition, for the first time an arc-normal extension of $${\sim }6~\hbox {mm/year}$$ has also been observed in the Tethyan Himalaya of Kumaon. Inverse modeling of GPS-derived surface deformation rates in Garhwal and Kumaon Himalaya using a single dislocation indicate that the Main Himalayan Thrust is locked from the surface to a depth of $${\sim }15{-}20~\hbox {km}$$ over a width of 110 km with associated slip rate of $${\sim }16{-}18~\hbox {mm/year}$$ . These results indicate that the arc-normal rates in the Northwest Himalaya have a complex deformation pattern involving both convergence and extension, and rigorous seismo-tectonic models in the Himalaya are necessary to account for this pattern. In addition, the results also gave an estimate of co-seismic and post-seismic motion associated with the 1999 Chamoli earthquake, which is modeled to derive the slip and geometry of the rupture plane. [ABSTRACT FROM AUTHOR]

The foremost Global Positioning System (GPS) derived measurements in the Kumaun Himalaya indicate that most of the crustal motion of the Indian plate is accommodating towards the base as well as on the hanging wall of Main Central Thrust (MCT). Deformation pattern within the Kumaun Himalaya varies from south to north and indicates maximum deformation rate near MCT. Our study, based on the campaign mode GPS survey during 2003-2006, reveals that the area between north of North Almora Thrust (NAT) and at the base of Great Himalaya registers maximum strain rate, which is lowered towards the Trans Himadri Fault (THF). The GAMIT-GLOBK processed campaign data of the area show that currently, the Himalayan Frontal Fault (HFF) and Main Boundary Thrust (MBT) are locked with the Indian plate, and a 6.7 ± 2.5 mm/yr of horizontal shortening is taking place between the Lesser Himalaya and Peninsular India. [ABSTRACT FROM AUTHOR]

The present study is an attempt to analyse the precipitable water vapour (PWV) derived from Global Positioning System (GPS) and observed meteorological data over Almora, Central Himalayan Region. The PWV values derived using GPS study is compared with the corresponding moderate resolution imaging spectro-radiometer (MODIS) data. The statistical analysis reveals a positive correlation between both methods. Moderate resolution imaging spectroradiometer near-infrared (MODIS NIR) clear column water vapour product shows a higher correlation ( R = 90-93 %) with GPS-derived precipitable water vapour on annual scale as compared to the seasonal scale ( R = 62-87 %). MODIS is found to be overestimating in NIR clear column where the magnitude of bias and RMSE show systematic changes from season to season. Monsoon is an important phenomenon in the Indian weather context and holds significant importance in Central Himalayan ecosystem. The monthly and seasonal variation in precipitable water vapour is related with monsoon onset in the region. Diurnal variations in precipitable water vapour are studied with other meteorological data over Almora during dry and wet season. The precipitable water vapour had minimum value in the morning, increases in the afternoon to evening and again decreases to the midnight in both the dry and wet seasons. These results suggest that diurnal variation of water vapour is caused by the transport of water vapour by thermally induced local circulation. [ABSTRACT FROM AUTHOR]

Deformation rates derived from GPS measurements made at two continuously operating stations at Leh (34.1°N, 77.6°E) and Hanle (32.7°N, 78.9°E), and eight campaign sites in the trans-Himalayan Ladakh spanning 11 years (1997-2008), provide a clear picture of the kinematics of this region as well as the convergence rate across northwestern Himalaya. All the Ladakh sites move 32-34 mm/year NE in the ITRF2005 reference frame, and their relative velocities are 13-16 mm/year SW in the Indian reference frame and ~19 mm/year W with reference to the Lhasa IGS station in southeastern Tibet. The results indicate that there is no statistically significant deformation in the 200-km stretch between the continuous sites Leh and Hanle as well as between Leh and Nubra valley sites along the Karakoram fault, whereas the sites in and around the splayed Karakoram fault region indicate surface deformation of 2.5 mm/year. Campaign sites along the Karakoram fault zone indicate a fault parallel surface motion of 1.4-2.5 mm/year in the Tangste and western Panamik segment of the Karakoram fault, which quantifies the best possible GPS-derived dextral slip rate of 3 mm/year along this fault during this 11-year period. Baselines of Ladakh sites show convergence rates of 15-18 mm/year with respect to south India and 12-15 mm/year with respect to Delhi in north India and Almora in the Himalaya ~400 km north-northeast of Delhi. These constitute an arc normal convergence of 12-15 mm/year across the western Himalaya, which is consistent with arc normal convergence all along the Himalayan arc from west to east. Baseline extension rates of 14-16 mm/year between Lhasa and Ladakh sites are consistent with the east-west extension rate of Tibetan Plateau. [ABSTRACT FROM AUTHOR]

The Gangotri glacier is retreating like other glaciers in the Himalaya and its volume and size are shrinking as well. Reoccupying the historical snout positions using Global Positioning System (GPS) in rapid static mode indicates the varying rates of retreat during different time-spans of the last century, with the total retreat of 1519.13 m in the last 69 years. Post 1971, the rate of retreat of the glacier has declined. Monitoring of glacier terminus using GPS survey in kinematic mode reveals that the glacier has retreated at much lower rate (12.10 ± 0.041 ma-1) between 2004 and 2005. The study further shows that the southern portion of the snout is retreating at significantly lower rate in comparison to the northern part. However, maximum recession (13.76 ± 0.048 m in 2004-05) took place along the centreline of the glacier. [ABSTRACT FROM AUTHOR]

The present study elucidates velocity of the Indian plate from 2013 to 2016 with the help of six continuously operating permanent Global Positioning System (GPS) stations and tracks the crustal motion and direction directly by means of space-based geodetic measurements. The GPS derived velocity estimates were computed with respect to 2008 International Terrestrial Reference Frame (ITRF 08) and carried out almost all along the arc in the Indian Himalayan Region (IHR). The velocity vectors indicate that the Indian plate is moving towards the NE direction (average velocity of 46.95 ± 0.23 mm/yr) with higher movement towards the eastward direction (36.11 ± 0.17 mm/yr) compared to the northward direction (29.02 ± 0.16 mm/yr). Variations in the plate motion between IISC and permanent GPS stations suggest that presently, the convergence rate is about 8.06 ± 0.28 mm/yr and 5.71 ± 0.17 mm/yr for Higher Himalaya and Lesser Himalaya respectively. In addition, the deformation rate was also calculated on the basis of baseline shortening between IGS stations (IISC and LHAZ) and permanent GPS stations. The results suggest that the deformation is about 11.68 ± 1.32 mm/yr above the Main Central Thrust (MCT) and 6.74 ± 1.20 mm/yr above the Main Boundary Thrust (MBT) with respect to the Indian plate (IISC), while it is 20.60 ± 1.76 mm/yr above the MCT and 11.42 ± 1.21 mm/yr above the MBT with respect to Eurasian plate (LHAZ). The strain rate through GPS measurement reveals that the maximum strain is accumulated in the central part of the Himalaya between the MBT and MCT, indicating vulnerability of the central Indian Himalaya for future earthquakes. [ABSTRACT FROM AUTHOR]

The regular monitoring of glaciers is important to determine their retreating rate and mass balance for overall glacier health. Chaturangi glacier, a major inactive tributary of the Gangotri glacier system was selected for the present study due to its dynamic nature and also because there are no previous records of its retreating rates. In order to reconstruct past retreat- ing rates, total area loss, volume change and shift in snout position were measured through multi-temporal satellite data from 1989 to 2016 and kinematic GPS survey from 2015 to 2016. The results obtained from satellite data indicate that in the last 27 years Chaturangi glacier snout has retreated 1172.57 ± 38.3 m (average = 45.07 ± 4.31 m/year) with a total area and volume loss of 0.626 ± 0.001 sq. km and 0.139 km3 respectively. The field measurements through differential global positioning system survey revealed that the annual retreating rate was 22.84 ±0.05 m/year. The large variations in results derived from both the methods are probably because of higher difference in their accuracy. Nevertheless, the results derived from both the methods are in agreement that Chaturangi glacier is retreating at a considerable rate. [ABSTRACT FROM AUTHOR]

Abstract No great earthquake has occurred in the Garhwal–Kumaun region of NW Himalaya in the past 500 years or more. We report results of continuous GPS measurements from 28 sites from the region to suggest that the convergence rate in this part of the Himalaya is about 18 mm/yr which is leading to strain accumulation in the region. The Main Himalayan Thrust (MHT) in the frontal part of the Himalaya under the Outer and southern Lesser Himalaya is strongly coupled for a width of about 85 km. The midcrustal ramp where earthquakes of Himalayan seismic belt occur, exhibits low coupling. Strong coupling on the MHT beneath the Outer and Lesser Himalaya is homogeneous except in the very shallow updip part of the MHT. Subduction of sediments of the Indo-Gangetic plains or the Delhi Hardwar ridge does not seem to influence coupling. A high rate of strain accumulation, which has continued for more than 500 years on a strongly coupled MHT makes this one of the most earthquake-vulnerable segments of the Himalayan arc. Graphical abstract Highlights • Locking variation on MHT beneath Garhwal Kumaun Himalaya from 28 cGPS measurements. • Long term convergence rate in the region is ∼18 mm/yr. • Strong locking on the MHT beneath the Outer and Lesser Himalaya. • Ramp is in transition from strongly coupled to aseismically slipping MHT. • Strong coupling, high strain rate for >500 yr makes it highly vulnerable segment. [ABSTRACT FROM AUTHOR]