Contrasting geometric and dynamic evolution of lake and land-terminating glaciers in the central Himalaya

Owen King,Duncan Quincey,Amaury Dehecq,Jonathan Carrivick

doi:10.1016/j.gloplacha.2018.05.006

Owen King, Duncan Quincey + Show 2 more

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https://doi.org/10.1016/j.gloplacha.2018.05.006

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Abstract

Abstract The impact of glacial lake development on the evolution of glaciers in the Himalaya is poorly quantified, despite the increasing prevalence of supraglacial and proglacial water bodies throughout the region. In this study we examine changes in the geometry, velocity and surface elevation of nine lake-terminating and nine land-terminating glaciers in the Everest region of the central Himalaya over the time period 2000 to 2015. The land-terminating glaciers we examined all decelerated (mean velocity change of −0.16 to −5.60 m a−1 for different glaciers), thinned most in their middle reaches, and developed a more gently sloping surface (−0.02 to −0.37° change) down-glacier over the period 2000–2015. The lake-terminating glaciers we examined all retreated (0.46 to 1.42 km), became steeper (0.04 to 8.68° change), and showed maximum thinning towards their termini, but differed in terms of their dynamics, with one group of glaciers accelerating (mean speed-up of 0.18 to 8.04 m a−1) and the other decelerating (mean slow-down of −0.36 m a−1 to −8.68 m a−1). We suggest that these two scenarios of glacier evolution each represent a different phase of glacial lake expansion; one that is accompanied by increasingly dynamic glacier behaviour and retreat, and a phase where glacial lakes have little impact on glacier behaviour that may precede or follow the phase of active retreat. Our observations are important because they quantify the interaction of glacial lake expansion with glacier ice mass loss, and show that increased glacier recession should be expected where a glacial lake has begun to develop.

Highlights

The number and size of proglacial lakes has increased dramatically across the Hindu Kush Karakoram Himalaya (HKKH) in recent decades (Zhang et al, 2015; Nie et al, 2017), and their expansion has been associated with areal and volumetric reductions in glacier extent (Basnet et al, 2013; King et al, 2017; Wang et al, 2017)
If simulations of Himalayan glacier evolution over coming decades are to be robust, it is imperative that we improve our understanding of the response of Himalayan glaciers to glacial lake growth
In this study we examine the evolution of nine lake-terminating and nine land-terminating glaciers in the Everest region of the central Himalaya, which is a region that has experienced a 20% increase in lake area from 2000 to 2009 (Gardelle et al, 2011)

Summary

Introduction

The number and size of proglacial (moraine- and ice-dammed) lakes has increased dramatically across the Hindu Kush Karakoram Himalaya (HKKH) in recent decades (Zhang et al, 2015; Nie et al, 2017), and their expansion has been associated with areal and volumetric reductions in glacier extent (Basnet et al, 2013; King et al, 2017; Wang et al, 2017). Reynolds et al (2000), Quincey et al (2007), and Sakai and Fujita (2010) identified a set of glacier surface characteristics conducive to supraglacial lake formation. They suggested that meltwater ponding and pond coalescence is most likely where the glacier surface has a surface gradient of < 2° and a negligible velocity, with steeper, faster glacier surfaces liable to meltwater runoff and/or fracturing that would promote meltwater drainage.

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