C21B-01: Glacier response to climate trend and climate variability in Mt. Everest region (Nepal)

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Authors: S. Thakuri1, 2, F. Salerno2, 3, N. Guyennon2, G. Viviano2, 3, C. Smiraglia1, 3, C. D'Agata1, G. Tartari2, 3

Author Institutions: 1. Graduate School of Earth, Environment and Biodiversity, University of Milan, Milan, MB, Italy. 2. Water Research Institute, National Research Council , Brugherio, MB, Italy. 3. Ev-K2-CNR Committee, Bergamo, BG, Italy.

This study is conducted with the aim of coupling the climatic dynamics with glaciers variations. The glaciers in the Mt. Everest region in Nepal Himalaya are characterized by the debris-mantle in most of their ablation zone and are controlled by the south-Asian summer monsoon and precipitation due to mid-latitude westerly. We analyzed variations in glacier surface and snowline altitude for the glaciers/ice mass in the Sagarmatha (Mt. Everest) National Park (area: 1148 km2), using cartography and remote imaging since 1950s to 2011 and uncertainties associated, providing a longest time series of glacier variations in this region. The glacier surface area had loss of 14.3±5.9 % (0.27 % yr-1) from 396.2 km2 to 339.5 km2 in 1958 to 2011 with the loss by 0.12 % yr-1 in 1958-75 and 0.70 % yr-1 in recent years. The smaller glaciers with <1 km2 dimension had decreased by 43% in their surface area showing rapid disappearance of very small glacier/ice mass. The accumulation area decreased by 24.8%, whist ablation area increased by 17.7 % with nearly 6% increase in debris-cover surface in ablation zone in 1958 to 2011. The accumulation and ablation area changes can be explained by SLA position which was continuously moving upward from 5279±144 m asl. in 1958 to 5472±209 m asl. in 2011 with the overall vertical shift of 192±9 m (3.6 m yr-1). The glaciers are showing the discordant behavior with individual glaciers varying spatially and temporally discern manner. Majority of glaciers are retreating but some glaciers observed as stationary or even advancing in certain period of analysis which could be explained by their location and topographic effect. We reconstructed temperature and precipitation complete series using the monthly quantile mapping and expectation maximization techniques from the all available insitu measurements in 1992-2011 from different automatic weather stations located in the Mt. Everest region and conducted the singular spectral analysis and monthly sequential Mann-Kendall test. The analysis indicated that annual temperature has increased by +0.03°C yr-1 with the increase in winter and pre-monsoon months but statistically significant only for winter months. The precipitation has decreased by around 180 mm in the analyzed period. The decreases in precipitation are statistically significant for both winter and summer precipitation. The stream-flow data indicates significantly widening of annual extreme discharge characteristics. Another, the longest time series of temperature and precipitation from the closest meteorological station (Kathmandu) also agree with this observation, indicating significant increase in temperature (1960s-2011) while the precipitation has statistically no significant trend until 1990s but significantly weakening trend in 1990s to 2011. We conclude by underlining that the observed variation of glacier surface and SLA could be explained jointly by increase of temperature and more importantly, by changes of precipitation for recent years as the glaciers in this region are controlled by summer-monsoon precipitation.

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