Pattern and imprints of elevation-dependent warming on central Himalayan cryosphere as revealed by Earth Observation datasets

Several studies have noted elevation-dependent warming (EDW) in the Himalaya. However, understanding of its spatio-temporal patterns and impacts on the cryosphere remains limited, given the complex geographic and climatic conditions of the central Himalayan region. In this novel attempt to comprehend EDW in the central Himalaya, we utilized multisource satellites and modeled data spanning 2000 to 2020. Our analysis examined temporal and altitudinal variations in land surface temperature (LST) and air temperature, considering changes in surface albedo and cryosphere elements. The multi-temporal glacier inventory revealed an overall decline in glacier area from 2,710km2 in 2000-01 to 2,658km2 in 2020-21. This receded glacier area contributed to the development/expansion of glacial lakes or exposed bedrock, potentially amplifying solar radiation absorption and exerting positive surface albedo feedback on localized heating and glacier melting. Concurrent with glacier retreat, pro- and peri-glacial lakes increased in area and number by ~28%, reaching 6.8km2 (209) in 2020, with a notable ~36% increase in area and ~32% in number above 4600m asl. Analysis of MODIS-derived land surface temperature and ERA5-Land modeled near-surface air temperature suggested an increasing temperature trend over the past two decades, with a higher rate of increase at higher elevations. Snow cover area and surface albedo, recorded from MODIS datasets, decreased, particularly at higher elevations, with temperature trends. These findings illustrate the pattern and impacts of EDW, which are expected to intensify due to the positive surface albedo feedback mechanism.