Abstract
Himalayan glaciers have shrunk rapidly in recent decades, but the spatial pattern of ice loss is highly variable and appears to be modulated by factors relating to individual glacier characteristics. This hinders our ability to predict their future evolution, which is vital for water resource management. The aim of this study is to assess recent glacier changes in the little-studied Annapurna Conservation Area (ACA; area: 7629 km2) in Nepal, and to explore local controls influencing their behaviour. We map changes in glacier area, surface elevation, and ice flow velocity on a large sample of glaciers (n = 162) in the ACA between 2000 and 2016. We found that total glacier area decreased by 8.5% between 2000 and 2014/15. Ice surface velocity changes between 2002 and 2016 were variable, with no clear trend of acceleration or deceleration. The mean surface elevation change for a smaller sample of glaciers (n = 72) was −0.33 ± 0.22 m a−1 between 2000 and 2013/16, which equates to a mean mass balance of −0.28 ± 0.24 m w.e. a−1. There was a trend of increasingly less negative mass balance towards the north. Glaciers that lost the most mass in the north of the ACA tended to have lower maximum elevations, bottom-heavy hypsometries, and were more likely to be avalanche-fed. However, these patterns were not apparent in glaciers in central ACA. There was no significant difference in the mean surface elevation change rate on the ablation zones of debris-covered compared with debris-free glaciers. Our work shows that glaciers in the ACA are losing area and mass at variable rates, but that the influence of local controls is complex, which introduces large uncertainties when predicting their future evolution.
Highlights
Glaciers in High Mountain Asia (HMA) are an important component of the global cryosphere [1]
There was no significant difference in the rank means of percentage area change in the Muktinath Himal and the Damodar Himal
Our study shows that glaciers in the Annapurna Conservation Area (ACA), central Nepal, thinned and lost mass and area between 2000 and 2016
Summary
Glaciers in High Mountain Asia (HMA) are an important component of the global cryosphere [1]. There are broad regional spatial variations in mass balance across HMA: the central and eastern Himalayas (Figure 1) show moderate mass losses (−0.22 to −0.33 m w.e. a−1); the western Himalayas have the highest rates of loss (−0.45 to −0.55 m w.e. a−1); and the Karakoram and Pamir (Figure 1) are in balance or even showing mass gains (−0.03 to + 0.14 m w.e. a−1) [2,6] These east to west gradients in ice loss are thought to reflect the greater influence of the Indian and East Asian monsoons in the central and eastern Himalayas versus the prevailing Mid Latitude Westerlies, which provide precipitation for glaciers in the northwest mountain ranges [8,9]. Glacier area change and mass loss show north
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