Monitoring of High Mountain Glaciers in the Vicinity of Everest (Himalaya) using Remote Sensing Capability

Abstract:

Himalayan glaciers are of crucial interest due to their role in the cryospheric system and hydrology. This contribution examines glacier changes between 1960s and 2013 using satellite data. The study is focused in 3 basins in Nepal: Upper Sun Koshi (USKB; 2850 km²), Dudh Koshi (DKB; 3720 km²), and Tamor (TB; 5875 km²). We observed an overall glacier surface loss of 0.19 ± 0.26 % a^-1 (146.1 to 136.9 km²) in SKB for 1975-2013 period; 0.27 ± 0.06 % a^-1 (404.6 to 351.8 km²) in the DKB for 1962-2011, and 8.4% (0.25 ± 0.29 % a^-1; 610.9 to 559.3 km²) in the TB for 1975-2009 period. In the DKB, we observed an upward shift of snow-line altitude (ΔSLA) by more than 180 m, a terminus retreat of on average ~ 400 m, and an increase of 17.6 ± 3.1% in debris coverage between 1962 and 2011. Moreover, we observed that (i) glaciers with increased debris cover have experienced a reduced termini retreat; (ii) negative mass balances (i.e., ΔSLA) induce increases of debris coverage; (iii) slight, but statistically insignificant acceleration of the surface area loss since early 1990s; but a significant loss for the largest glaciers (>10 km²) that have accumulation zones at higher elevations and along the preferable south–north direction of the monsoon; (iv) a significant ΔSLA; moreover, the largest glaciers present median ΔSLA that are nearly double than that of the smallest; this finding leads to a hypothesis that these glaciers are shrinking, not only due to warming temperatures, but also as a result of decreasing precipitation due to a weakening Asian monsoons registered over the last few decades. Furthermore, we present first results on the geodetic glacier mass and velocity changes of selected glaciers, and climatic trends. In fact, less accumulation due to the observed decrease of precipitation should cause lower glacier flow velocity until to the ice stagnation of tongues as observed by other previous studies in the region. Finally, we compared our findings with other studies in the high mountain Asia and conclude that the shrinkage of these glaciers are less than that of western and eastern Himalaya, and southern and eastern Tibetan Plateau. The location in higher elevations have likely reduced the impact of warming on these glaciers, but have not been excluded from a relentlessly continuous and slow recession process over the past 50 yrs.