Factors controlling the accelerated expansion of Imja Lake, Mount Everest region, Nepal

Sudeep Thakuri,Tobias Bolch,Franco Salerno,Nicolas Guyennon,Gianni Tartari

doi:10.3189/2016aog71a063

Abstract

AbstractThis study explores the link between area increase of Imja Tsho (Lake) and changes of Imja Glacier (area ~25km2) under the influence of climate change using multitemporal satellite imagery and local climate data. Between 1962 and 2013, Imja Lake expanded from 0.03±0.01 to 1.35±0.05 km2 at a rate of 0.026±0.001 km2 a-1. The mean glacier-wide flow velocity was 37±30ma-1 during 1992–93 and 23±15ma-1 during 2013–14, indicating a decreasing velocity. A mean elevation change of –1.29±0.71ma-1 was observed over the lower part of the glacier in the period 2001–14, with a rate of –1.06±0.63ma-1 in 2001–08 and –1.56±0.80ma-1 in 2008–14. We conclude that the decrease in flow velocity is mainly associated with reduced accumulation due to a decrease in precipitation during the last few decades. Furthermore, glacier ablation has increased due to increasing maximum temperatures during the post-monsoon months. Decreased glacier flow velocities and increased mass losses induce the formation and subsequent expansion of glacial lakes under favourable topographic conditions.

Highlights

The Everest region is characterized by large debris-covered glaciers (Fujii and Higuchi, 1977) and many glacial lakes (Gardelle and others, 2011; Salerno and others, 2012)
According to Salerno and others (2012), three types of glacial lakes are present in this region: (1) supraglacial lakes, which evolved and are located on the surfaces of glaciers; (2) proglacial lakes, which are moraine-dammed lakes in contact with glaciers; and (3) unconnected lakes, which are not directly connected to glaciers, but may have a glacier located in their basin
Previous studies revealed that the area of proglacial lakes on the southern slopes of Mount Everest has increased since the early 1960s (Bolch and others, 2008a; Tartari and others, 2008; Gardelle and others, 2011)

Summary

Introduction

The Everest region is characterized by large debris-covered glaciers (Fujii and Higuchi, 1977) and many glacial lakes (Gardelle and others, 2011; Salerno and others, 2012). Many studies have indicated that current moraine- or ice-dammed lakes are the result of coalescence and growth of supraglacial lakes (e.g. Fujita and others, 2009; Watanabe and others, 2009; Thompson and others, 2012). Such lakes pose a potential threat of glacial lake outburst flood (GLOF; e.g. Richardson and Reynolds, 2000; Bajracharya and others, 2007; Benn and others, 2012), with consequent loss of human lives and property in the downstream valley. Imja Tsho (Lake) is one of several proglacial lakes in the Everest region that evolved in the early 1960s from a small pond and subsequently expanded (Bolch and others, 2008a; SomosValenzuela and others, 2014). This lake has been of great research interest due to its potential risk (e.g. Yamada, 1998; Bajracharya and others, 2007; Fujita and others, 2009)

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Conclusion