Abstract
Abstract. Snow cover changes have a direct bearing on the regional and global energy and water cycles and the change in the Earth's climate conditions. We studied the relatively long-term (2000–2017) altitudinal spatiotemporal changes in the coverage of snow and glaciers in one of the world's largest mountainous regions, the Hindu Kush Himalayan (HKH) region, including Tibet, using remote sensing data (5 km grid resolution) from the Moderate Resolution Imaging Spectroradiometer (MODIS) on board the Terra satellite. This dataset provided a unique opportunity to study zonal and hypsographic changes in the intra-annual (accumulating season and melting season) and interannual variations in snow and glacial cover over the HKH region. The zonal and altitudinal (hypsographic) analyses were carried out for the melting season and accumulating season. The altitude-wise linear trend analysis (Pearson's) of snow cover, shown as a hypsographic curve, clearly indicates a major decline in snow cover (average of 5 % or more at 100 m interval aggregates) between 4000–4500 and 5500–6000 m altitudes, which is consistent with the median trend (Theil–Sen – TS) and the monotonic trend (Mann–Kendall – MK; statistics) analysis. This analysis also revealed the regions and altitudes where major and statistically significant increases (10 % to 30 %) or decreases (−10 % to −30 %) in snow cover are identified. The extrapolation of the altitude-wise linear trend shows that it may take between ∼ 74 and 7900 years, for 3001–6000 and 6000–7000 m altitude zones respectively, for mean snow cover to decline approximately 25 % in the HKH. More detailed analysis based on longer observational records and model simulations is warranted to better understand the underlying factors, processes, and feedbacks that affect the dynamic of snow cover in HKH. These preliminary results suggest a need for continued monitoring of this highly sensitive region to climate variability and change that depends on snow as a major source of freshwater for all human activities.
Highlights
Understanding the impact of snow cover variability with respect to altitude and temperature in the Hindu Kush Himalayan region (HKH; Immerzeel et al, 2010; Shrestha et al, 2015) is of great importance for regional water availability and understanding of climate change in this highly populated region of the world
The average long-term snow cover is found to be 35.9 % (Table 1); the northwestern region ( Zone 2) shows much higher snow cover as some of the largest glaciers and permanent snow-covered areas are within this zone
The peak in snow cover is observed during February (48.8 %), and the lows are observed during August
Summary
Understanding the impact of snow cover variability with respect to altitude and temperature in the Hindu Kush Himalayan region (HKH; Immerzeel et al, 2010; Shrestha et al, 2015) is of great importance for regional water availability and understanding of climate change in this highly populated region of the world. The HKH region is projected to show a substantial loss of glacial mass and area in the coming decades (Bolch et al, 2012). The snow cover and glaciers of the high-altitude regions of HKH, including Tibet, are likely to be one of the regions most affected by the projected rise in global temperatures by about. N. Desinayak et al.: Snow cover variability and trend over the Hindu Kush Himalayan region
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