Multi-decadal mass loss of glaciers in the Everest area (Nepal Himalaya) derived from stereo imagery

Abstract

Abstract. Mass loss of Himalayan glaciers has wide-ranging consequences such as changing runoff distribution, sea level rise and an increasing risk of glacial lake outburst floods (GLOFs). The assessment of the regional and global impact of glacier changes in the Himalaya is, however, hampered by a lack of mass balance data for most of the range. Multi-temporal digital terrain models (DTMs) allow glacier mass balance to be calculated. Here, we present a time series of mass changes for ten glaciers covering an area of about 50 km 2 south and west of Mt. Everest, Nepal, using stereo Corona spy imagery (years 1962 and 1970), aerial images and recent high resolution satellite data (Cartosat-1). This is the longest time series of mass changes in the Himalaya. We reveal that the glaciers have been significantly losing mass since at least 1970, despite thick debris cover. The specific mass loss for 1970-2007 is 0.32 ± 0.08 m w.e. a −1 , however, not higher than the global average. Comparisons of the recent DTMs with earlier time periods indicate an accelerated mass loss. This is, however, hardly statistically significant due to high uncertainty, especially of the lower resolution ASTER DTM. The characteristics of surface lowering can be explained by spatial variations of glacier velocity, the thickness of the debris-cover, and ice melt due to exposed ice cliffs and ponds.

Future Hydrological Regimes in the Upper Indus Basin: A Case Study from a High-Altitude Glacierized Catchment

“…Along the HKH range, there is considerable variability in climate conditions, including varying precipitation sources and types (e.g., Bocchiola and Diolaiuti 2013), influencing the behavior and evolution of the cryosphere. Eastern and central HKH glaciers are subject to general retreat and have lost a significant amount of mass and area in the last few decades (Bolch et al 2011).…”

“…Glaciers in the eastern part of the HKH receive their water input in summer owing to the monsoon, while in the west, precipitation occurs mainly in winter, carried by western weather patterns (Fowler and Archer 2005;Winiger et al 2005;Bookhagen and Burbank 2010;Kääb et al 2012). This variability in accumulation conditions may be one reason for the large spread in glacier changes within the whole region (Bolch et al 2011;Kääb et al 2012). Kääb et al (2012) used satellite laser altimetry to show widespread glacier wastage in the eastern, central, and southwestern parts of the HKH, while in the Karakoram, glaciers seem to have thinned by a few centimeters per year.…”

Glacier characteristics and changes in the Sary-Jaz River Basin (Central Tien Shan, Kyrgyzstan) – 1990–2010

“…However, it should be mentioned that heavily debris-covered glaciers in the Himalaya and south of Peak Pobeda close to our study region show clear mass loss despite a thick debris cover and low area loss (cf. Bolch et al 2011, Pieczonka et al 2013, which is likely due to enhanced melting at exposed ice cliffs and supra-glacial ponds that are common at debris-covered glaciers (Benn et al 2012).…”

Brief communication: Observations of a glacier outburst flood from Lhotse Glacier, Everest area, Nepal

“…During the last half-century, debris-covered glaciers in the Everest region have experienced significant mass loss (e.g., Bolch et al, 2011), which has led to the development of glacial lakes and supraglacial ponds (Benn et al, 2012). Proglacial lakes may develop if the surface gradient of the glacier is gentle (< 2 • ), while steeper gradients (> 2 • ) will help drain these ponds (Quincey et al, 2007).…”

“…For debris-covered glaciers, the drainage of supraglacial ponds commonly occurs through englacial conduits, which facilitate connections to areas of lower hydraulic potential (Gulley and Benn, 2007). These englacial conduits develop on debris-covered glaciers in the Himalaya through cut-and-closure mechanisms associated with meltwater streams, the exploitation of high-permeability areas that provide alternative pathways to the impermeable glacier ice, and through hydrofracturing processes (Gulley and Benn, 2007;Benn et al, 2009; Gulley et al, 2009a, b).During the last half-century, debris-covered glaciers in the Everest region have experienced significant mass loss (e.g., Bolch et al, 2011), which has led to the development of glacial lakes and supraglacial ponds (Benn et al, 2012). Proglacial lakes may develop if the surface gradient of the glacier is gentle (< 2 • ), while steeper gradients (> 2 • ) will help drain these ponds (Quincey et al, 2007).…”