Spatio-temporal change delineation and forecasting of snow/ice-covered areas of Sikkim Himalaya using multispectral and thermal band combinations of landsat imagery

The widespread retreat of snow/ice-covered areas from the past century has given rise to the sea level. The snow/ice-covered area of Sikkim Himalaya is not an exception. Snow-covered areas are disappearing at an alarming rate, which would give rise to water scarcity especially to the population dwelling in the mountainous regions. Changes in the snow/ice-covered areas indicate a huge threat to the changing climate. Therefore, snow cover area monitoring is currently an important aspect of climate change studies. Landsat data are widely accepted and immensely valued for snow cover mapping. An assessment through change delineation has been performed for the images acquired during the accumulation period of snow for the years 1998, 2008, and 2018 and another three acquired during the ablation period for the years 2000, 2009, and 2017. Snow Cover Index (S3) and Normalized Difference Snow Thermal Index (NDSTI) techniques have been applied to the images. A newly proposed snow index called Perennial Snow Index (PSI) has been applied to delineate the perennial snow-covered regions using the difference of reflectance observed in a visible band (RED) and the Thermal infrared (TIR) band divided by the sum of the two reflectances of Landsat 8 after resampling to 15meter resolution through merging with panchromatic data. The acquired results demarcated the thick or perennial snow accumulated areal boundaries from the surrounding lesser snow deposited regions. The temporal change analysis of two decades shows a difference of 10% in the extent of the snow cover region in Sikkim Himalayas. S3 index values were taken into consideration while performing a Time series analysis. The observed values show a declining trend line along with forecasts till the year 2030. Global Land Ice Measurement from Space (GLIMS) program and Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) Global Digital Elevation Map (GDEM) data have been used for reference