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The Himalayan glaciers contribute significantly to regional water resources. However, limited field observations restrict our understanding of glacier dynamics and behaviour. Here, we investigated the long-term in situ mass balance, meteorology, ice velocity and discharge of the Chhota Shigri Glacier. The mean annual glacier-wide mass balance was negative, −0.46 ± 0.40 m w.e. a−1 for the period 2002–2019 corresponding to a cumulative wastage of −7.87 m w.e. Winter mass balance was 1.15 m w.e. a−1 and summer mass balance was −1.35 m w.e. a−1 over 2009–2019. Surface ice velocity has decreased on average by 25–42% in the lower and middle ablation zone (below 4700 m a.s.l.) since 2003; however, no substantial change was observed at higher altitudes. The decrease in velocity suggests that the glacier is adjusting its flow in response to negative mass balance. The summer discharge begins to rise from May and peaks in July, with a contribution of 43%, followed by 38% and 19% in August and September, respectively. The discharge pattern closely follows the air temperature. The long-term observation on the ‘Chhota Shigri – a benchmark glacier’, shows a mass wastage which corresponds to the slowdown of the glacier in the past two decades.

Abstract. Analysis of surface energy balance (SEB) at the glacier/snow surface is the most comprehensive way to explain the atmosphere–glacier/snow interactions, but that requires extensive data. In this study, we have analysed an 11-year (2009–2020) record of the meteorological dataset from an automatic weather station installed at 4863 ma.s.l. (above sea level) on a lateral moraine of the Chhota Shigri Glacier, western Himalaya. The study was carried out over the winter months (December to April) to understand SEB drivers and snow loses through sublimation. Furthermore, this study examines the role of cloud cover on SEB and turbulent heat fluxes. The turbulent heat fluxes were calculated using the bulk-aerodynamic method, including stability corrections. The net short-wave radiation was the primary energy source. However, the turbulent heat fluxes dissipated a significant amount of energy. The cloud cover plays an important role in limiting the incoming short-wave radiation by about 70 %. It also restricts the turbulent heat fluxes by more than 60 %, resulting in lower snow sublimation. During winter, turbulent latent heat flux contributed the largest proportion (64 %) in the total SEB, followed by net radiation (25 %) and sensible heat flux (11 %). Sublimation rates were 3 times higher in clear-sky than overcast conditions, indicating a strong role of cloud cover in shaping favourable conditions for turbulent latent heat flux by modulating the near-surface boundary layer conditions. Dry air, along with high snow-surface temperature and wind speed, favours sublimation. Besides, we also observed that strong and cold winds, possibly through mid-latitude western disturbances, impede sublimation by bringing high moisture content to the region and cooling the snow surface. The estimated snow sublimation fraction was 16 %–42 % of the total winter snowfall at the study site. This study substantiates that the snow sublimation is an essential variable to be considered in glaciohydrological modelling at the high-mountain Himalayan glacierised catchments.

We present the first-ever mass-balance (MB) observation (2014–19), reconstruction (between 1978 and 2019) and sensitivity of debris-free Stok glacier (33.98°N, 77.45°E), Ladakh Region, India. In-situ MB was negative throughout the study period except in 2018/19 when the glacier witnessed a balanced condition. For MB modelling, three periods were considered based on the available data. Period I (1978–87, 1988/89) witnessed a near balance condition (−0.03 ± 0.35 m w.e. a−1) with five positive MB years. Whereas Period II (1998–2002, 2003–09) and III (2011–19) experienced high (−0.9 ± 0.35 m w.e. a−1) and moderate (−0.46 ± 0.35 m w.e. a−1) negative MBs, respectively. Glacier area for these periods was derived from the Corona, Landsat and PlanetScope imageries using a semi-automatic approach. The in-situ and modelled MBs were in good agreement with RMSE of 0.23 m w.e. a−1, R2 = 0.92, P < 0.05. The average mass loss was moderate (−0.47 ± 0.35 m w.e. a−1) over 28 hydrological years between 1978 and 2019. Sensitivity analysis showed that the glacier was more sensitive to summer temperature (−0.32 m w.e. a−1 °C−1) and winter precipitation (0.12 m w.e. a−1 for ± 10%). It was estimated that ~27% increase in precipitation is required on Stok glacier to compensate for the mass loss due to 1°C rise in temperature.

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Improving the knowledge on Himalayan glaciers mass balance is a key to understand the present and past annual atmospheric variations and future water availability in the region. Here, we present glaciological mass balance for Patsio Glacier, located in Himachal Pradesh (India), western Himalaya. Annual glacier-wide mass balance was measured for 7 consecutive years (2010/11 to 2016/17) and winter mass balance for 6 years (2011/12 to 2016/17). The cumulative mass balance over this period was −2.35 ± 0.37 m w.e. The corresponding mean mass balance was −0.34 m w.e. a−1. The mean annual ablation gradient excluding the debris-covered area was 0.47 m w.e. (100 m)−1. The annual ablation over the debris-covered area is reduced by an average of −1.0 m w.e. compared to the clean ice surface. Winter mass balance was consistently positive with a maximum of 1.34 m w.e. in 2014/15 and a minimum of 0.88 m w.e. in 2011/12. Multiple regression analysis between annual mass balance versus annual and winter precipitation of the Lahaul-Spiti region shows a significant positive correlation. Our results highlight the importance of monitoring seasonal mass balance and consideration of non-climatic parameters (debris and aspect) while estimating the glacier-wide mass balance.

Abstract. Analysis of surface energy balance (SEB) at the glacier surface is the most comprehensive way to explain the atmosphere-glacier interactions but that requires extensive data. In this study, we analyse an 11-year (2009–2020) record of the meteorological dataset from an automatic weather station installed at 4863 m a.s.l., on a lateral moraine of the Chhota Shigri Glacier in the western Himalaya. The study was carried out over the winter months (December to April) to understand SEB drivers and snow sublimation. Further, we examine the role of cloud cover on SEB and turbulent heat fluxes. The turbulent heat fluxes were calculated using the bulk-aerodynamic method, including stability corrections. The net short-wave radiation was the primary energy source. However, the turbulent heat fluxes dissipated a significant amount of energy. The cloud cover plays an important role in limiting the incoming short-wave radiation by 70 %. It also restricts the turbulent heat fluxes by around 50 %, consequently less snow sublimation. During the winter period, turbulent latent heat flux contributed the largest (63 %) in the total SEB, followed by net all-wave radiation (29 %) and sensible heat flux (8 %). Sublimation rates were three times higher in clear-sky conditions than overcast, indicating a strong control of cloud cover in turbulent latent heat flux. Dry air, along with the high snow surface temperature and wind speed, favours sublimation. We also observed that strong and cold winds, possibly through mid-latitude western disturbances, impede sublimation by bringing high moisture content in the region and cooling the snow surface. The estimated snow sublimation fraction was 16–42 % of the total winter snowfall at the study site. This indicates snow sublimation is an essential parameter to be considered in the glaciohydrological modelling at the high mountain Himalayan catchments.