Abstract
ABSTRACTThree debris-free glaciers with strongly differing annual glaciological glacier-wide mass balances (MBs) are monitored in the Everest region (central Himalaya, Nepal). The mass budget of Mera Glacier (5.1 km2in 2012), located in the southern part of this region, was balanced during 2007–15, whereas Pokalde (0.1 km2in 2011) and West Changri Nup glaciers (0.9 km2in 2013), ~30 km further north, have been losing mass rapidly with annual glacier-wide MBs of −0.69 ± 0.28 m w.e. a−1(2009–15) and −1.24 ± 0.27 m w.e. a−1(2010–15), respectively. An analysis of high-elevation meteorological variables reveals that these glaciers are sensitive to precipitation, and to occasional severe cyclonic storms originating from the Bay of Bengal. We observe a negative horizontal gradient of annual precipitation in south-to-north direction across the range (≤−21 mm km−1, i.e. −2% km−1). This contrasted mass-balance pattern over rather short distances is related (i) to the low maximum elevation of Pokalde and West Changri Nup glaciers, resulting in years where their accumulation area ratio is reduced to zero and (ii) to a steeper vertical gradient of MB for glaciers located in the inner arid part of the range.
Highlights
The current status of Hindu-Kush Karakoram Himalaya (HKKH) glaciers varies across the region from equilibrium or even slight mass gain in Karakoram in recent years (Hewitt, 2005; Gardelle and others, 2013) to rapid shrinkage and downwasting in the Himalayas (Bolch and others, 2012; Yao and others, 2012)
Mount Everest and its region in Nepal, central Himalaya, have drawn the attention of a growing number of scientists, such as glaciologists, highmountain hydrologists and climatologists, because of its symbolic significance as the highest mountain on Earth and large socio-economic impacts on tourism and water supply. In this region of investigation, four different studies using remotesensing techniques reported a mass loss over the last decades: region-wide mass balance (MB) of −0.32 ± 0.08 m w.e. a−1 from 1970 to 2007, over a 62 km2 glacierized area including Khumbu Glacier originating on Mount
The main objectives of this study are to: (i) present results from extensive MB measurements performed on debris-free Mera, Pokalde and West Changri Nup glaciers in the Everest region since 2007, and (ii) identify the drivers explaining the MB differences between these glaciers using previously unpublished meteorological data recorded at the glacier elevations
Summary
The current status of Hindu-Kush Karakoram Himalaya (HKKH) glaciers varies across the region from equilibrium or even slight mass gain in Karakoram in recent years (Hewitt, 2005; Gardelle and others, 2013) to rapid shrinkage and downwasting in the Himalayas (Bolch and others, 2012; Yao and others, 2012) Interpreting this contrasted signal in terms of climate is challenging because meteorological observations at glacier elevations are difficult and only recent and sparse (Fowler and Archer, 2006; Dimri and Dash, 2012). Based on extensive field work conducted from November 2011 to November 2015, Vincent and others (2016) quantified a 1.8 m w.e. a−1 reduction of area-averaged ablation between 5240 and 5525 m a.s.l. on the debris-covered North Changri Nup Glacier due to the presence of an insulating debris cover over its tongue
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