Temperature and precipitation changes over the glaciated parts of Indian Himalayan Region during 1901-2016.

The existing knowledge on long-term climate trends over glaciated parts of Indian Himalayan Region (IHR) is limited. The present study aims at assessing the long-term (1901-2016) as well as the recent (1990-2016) temperature and precipitation trends over the glaciated parts of western (WH), central (CH) and eastern Himalaya (EH) within the IHR using Climate Research Unit Time Series version 4.01 (CRU TS4.01) data. Mann-Kendall and Sen's slope estimator tests were employed to determine the monotonic trend direction and magnitude of change over time on annual and seasonal basis. The temperature and precipitation trends were quantitatively assessed here in terms of percent change over mean as well as in absolute terms. Results show that annual average temperature remains > 0 °C in WH (2.26 °C) and CH (3.24 °C) but < 0 °C in EH (-0.97 °C). Long-term analysis (1901-2016) reveals the maximum warming in EH (74.67% or 0.93 °C) followed by WH (52.56% or 0.64 °C) and minimum in CH (44.31% or 0.73 °C). The winter warming is notably higher (WH: 1.11 °C, CH: 1.19 °C and EH: 1.41 °C) than the summer (WH: 0.31 °C, CH: 0.26 °C and EH: 0.54 °C). Annual precipitation gradually increases from WH (535.57 mm) to CH (749.91 mm) to EH (1249.49 mm), of which 68%, 76%, and 90% respectively, are summer-induced. Nevertheless, precipitation showed no clear trend in WH (slight increase of 4.53%) and EH (slight decrease of -5.30%), but a clear reduction in CH (-19.25%). Seasonally, precipitation decreased in winter (-4.53%) but increased in summer (10.65%) in WH, clearly decreased in both winter (-24.69%) and summer (-17.01%) in CH, and slightly increased in winter (2.21%) but decreased in summer (-6.80%) in EH. In recent decades (1990-2016), warming trend further accelerated in WH (0.95 °C) and CH (1.01 °C) but decreased in EH (0.60 °C). The overall precipitation trends also changed during 1990-2016 as WH experienced an overall reduction (-5%), CH maintained a declining trend (-13.10%), and EH showed slight increase (1.01%). The study concludes that the climate of glaciated parts has changed significantly, but the trend and magnitude is highly heterogeneous over different regions which likely influenced the glaciated environment.

Revisiting the 24 year (1994-2018) record of glacier mass budget in the Suru sub-basin, western Himalaya: Overall response and controlling factors.

Glacier mass balance time-series measurements have immense importance in comprehending the overall regional hydrology and meteorology of the mountain systems. Such assessments are critical in the Indus River basin (compared to the Ganga and Brahmaputra), which besides having a significant contribution from the glaciers, also exhibits considerable heterogeneity in glacier response. Thus, to quantify this variability in glacier behavior and thereby develop a comprehensive understanding of the past as well as the future evolution of the glaciers, we reconstruct the annual surface mass balance records of 75 glaciers (size >1 km2) in the Suru sub-basin, western Himalaya for the period 1994-2018. We apply a remote sensing-based equilibrium line altitude-mass balance approach, supported by geodetic mass balance estimates (for 18 major glaciers) and limited field measurements. Our findings suggest a persistent negative mass balance of the glaciers (average: -0.69 ± 0.28 m w.e.a-1, cumulative: -16.56 m w.e), varying from -0.46 ± 0.27 (1997) to -0.79 ± 0.28 (2018) m w.e.a-1 during the study period. This overall mass loss coincides with an increased temperature (Tavg increased 0.5 °C; Tmin increased 0.27 °C; Tmax increased 0.06 °C) and reduced precipitation (by 4%) in the valley during 1994-2018, which shows the sensitivity of these glaciers to climate change. Within the Suru sub-basin, smaller, cleaner and high-altitude mountain glaciers of the Ladakh range have experienced greater mass loss (cumulative: -20.88 m w.e) compared to the Greater Himalayan range (cumulative: -13.44 m w.e). We observe latitudinal variability in mass loss in the Western Himalaya, with the highest mass loss rates in the Greater Himalayan Range (>-0.9 m w.e.a-1) and lowest in the Karakoram Range (<-0.1 m w.e.a-1), suggesting a transitional response of the Suru sub-basin glaciers (-0.69 m w.e.a-1). The overall regional picture suggests synchronicity in the mass loss pattern of western Himalayan glaciers, predominantly controlled by the climatic conditions. Meanwhile, the variability in their mass loss rates is attributed to the unique glacier characteristics.