Glacial and geomorphic effects of a supraglacial lake drainage and outburst event, Everest region, Nepal Himalaya

Abstract. A set of supraglacial ponds filled rapidly between April and July 2017 on Changri Shar Glacier in the Everest region of Nepal, coalescing into a ∼180 000 m2 lake before sudden and complete drainage through Changri Shar and Khumbu glaciers (15–17 July). We use PlanetScope and Pléiades satellite orthoimagery to document the system's evolution over its very short filling period and to assess the glacial and proglacial effects of the outburst flood. We also use high-resolution stereo digital elevation models (DEMs) to complete a detailed analysis of the event's glacial and geomorphic effects. Finally, we use discharge records at a stream gauge 4 km downstream to refine our interpretation of the chronology and magnitude of the outburst. We infer largely subsurface drainage through both of the glaciers located on its flow path, and efficient drainage through the lower portion of Khumbu Glacier. The drainage and subsequent outburst of 1.36±0.19×106 m3 of impounded water had a clear geomorphic impact on glacial and proglacial topography, including deep incision and landsliding along the Changri Nup proglacial stream, the collapse of shallow englacial conduits near the Khumbu terminus and extensive, enhanced bank erosion at least as far as 11 km downstream below Khumbu Glacier. These sudden changes destroyed major trails in three locations, demonstrating the potential hazard that short-lived, relatively small glacial lakes pose.

[1]  M. Moss,et al.  The Extremes of the Extremes: Extraordinary Floods , 2002 .

[2]  Peter Jansson,et al.  The concept of glacier storage: a review , 2003 .

[3]  Joseph M. Shea,et al.  Ice cliff contribution to the tongue-wide ablation of Changri Nup Glacier, Nepal, central Himalaya , 2018, The Cryosphere.

[4]  Georg Veh,et al.  Detecting Himalayan glacial lake outburst floods from Landsat time series , 2018 .

[5]  Joseph M. Shea,et al.  Reduced melt on debris-covered glaciers: investigations from Changri NupGlacier, Nepal , 2016 .

[6]  Evan S. Miles,et al.  Spatial, seasonal and interannual variability of supraglacial ponds in the Langtang Valley of Nepal, 1999–2013 , 2017 .

[7]  Robert C. Richardson,et al.  Heterogeneous water storage and thermal regime of supraglacial ponds on debris‐covered glaciers , 2018 .

[8]  Takeo Tadono,et al.  Seasonal drainage of supraglacial lakes on debris-covered glaciers in the Tien Shan Mountains, Central Asia , 2017 .

[9]  D. Benn,et al.  Structural control of englacial drainage systems in Himalayan debris-covered glaciers , 2007 .

[10]  Yves Arnaud,et al.  Contrasted evolution of glacial lakes along the Hindu Kush Himalaya mountain range between 1990 and 2009 , 2011 .

[11]  D. Shean.  High Mountain Asia 8-meter DEM Mosaics Derived from Optical Imagery, Version 1 , 2017 .

[12]  Andrew G. Fountain,et al.  Water flow through temperate glaciers , 1998 .

[13]  S. K. McFeeters.  The use of the Normalized Difference Water Index (NDWI) in the delineation of open water features , 1996 .

[14]  S. M. Jong,et al.  High-resolution monitoring of Himalayan glacier dynamics using unmanned aerial vehicles , 2014 .

[15]  A. Kääb,et al.  Glacial lake mapping with very high resolution satellite SAR data , 2012 .

[16]  Alun Hubbard,et al.  Supraglacial Ponds Regulate Runoff From Himalayan Debris‐Covered Glaciers , 2017 .

[17]  Fiona S. Tweed,et al.  A global assessment of the societal impacts of glacier outburst floods , 2016 .

[18]  D. Benn,et al.  Mechanisms of englacial conduit formation and their implications for subglacial recharge , 2009 .

[19]  Evan S. Miles,et al.  Pond Dynamics and Supraglacial-Englacial Connectivity on Debris-Covered Lirung Glacier, Nepal , 2017, Front. Earth Sci..

[20]  Koji Fujita,et al.  Distribution Characteristics and Energy Balance of Ice Cliffs on Debris-covered Glaciers, Nepal Himalaya , 2002 .

[21]  S. M. Jong,et al.  Object-based analysis of unmanned aerial vehicle imagery to map and characterise surface features on a debris-covered glacier , 2016 .

[22]  Yongwei Sheng,et al.  An inventory of historical glacial lake outburst floods in the Himalayas based on remote sensing observations and geomorphological analysis , 2018 .

[23]  John E. Costa,et al.  OUTBURST FLOODS FROM GLACIER-DAMMED LAKES: THE EFFECT OF MODE OF LAKE DRAINAGE ON FLOOD MAGNITUDE , 1996 .

[24]  N. Glasser,et al.  Field Techniques in Glaciology and Glacial Geomorphology , 2005 .

[25]  Laura A. Edwards,et al.  Glacier change and glacial lake outburst flood risk in the Bolivian Andes , 2016 .

[26]  A. Luckman,et al.  A cut-and-closure origin for englacial conduits in uncrevassed regions of polythermal glaciers , 2009, Journal of Glaciology.

[27]  Y. Arnaud,et al.  Contrasted surface mass balances of debris-free glaciers observed between the southern and the inner parts of the Everest region (2007–15) , 2017, Journal of Glaciology.

[28]  K. Fujita,et al.  Debris-covered glacier anomaly? Morphological factors controlling changes in the mass balance, surface area, terminus position, and snow line altitude of Himalayan glaciers , 2017 .

[29]  B. Brock,et al.  An investigation of the influence of supraglacial debris on glacier-hydrology , 2015 .

[30]  N. Glasser,et al.  Modelling the feedbacks between mass balance, ice flow and debris transport to predict the response to climate change of debris-covered glaciers in the Himalaya , 2015 .

[31]  Richard T. Cooper,et al.  Evidence for seasonal subglacial outburst events at a polythermal glacier, Finsterwalderbreen, Svalbard , 2001 .

[32]  Laurence C. Smith,et al.  Tracking Dynamic Northern Surface Water Changes with High-Frequency Planet CubeSat Imagery , 2017, Remote. Sens..

[33]  Adrian Luckman,et al.  Early recognition of glacial lake hazards in the Himalaya using remote sensing datasets , 2007 .

[34]  D. Benn,et al.  Growth and drainage of supraglacial lakes on debris-mantled Ngozumpa Glacier, Khumbu Himal, Nepal , 2001, Journal of Glaciology.

[35]  Jakob F. Steiner,et al.  Brief communication: The Khurdopin glacier surge revisited - Extreme flow velocities and formation of a dammed lake in 2017 , 2017 .

[36]  N. Otsu.  A threshold selection method from gray level histograms , 1979 .

[37]  Adrian Luckman,et al.  A rapidly growing moraine-dammed glacial lake on Ngozumpa Glacier, Nepal , 2012 .

[38]  F. Salerno,et al.  Quantifying Debris Thickness of Debris‐Covered Glaciers in the Everest Region of Nepal Through Inversion of a Subdebris Melt Model , 2018 .

[39]  A. Luckman,et al.  Structure and evolution of the drainage system of a Himalayan debris-covered glacier, and its relationship with patterns of mass loss , 2017 .

[40]  R. Hock,et al.  Glacier-dammed lake outburst events of Gornersee, Switzerland , 2007, Journal of Glaciology.

[41]  Katrin Röhl,et al.  Characteristics and evolution of supraglacial ponds on debris-covered Tasman Glacier, New Zealand , 2008, Journal of Glaciology.

[42]  Tobias Bolch,et al.  Response of debris-covered glaciers in the Mount Everest region to recent warming, and implications for outburst flood hazards , 2012 .

[43]  M. Westoby,et al.  Modelling outburst floods from moraine-dammed glacial lakes , 2014 .

[44]  Finnur Pálsson,et al.  Glacier topography and elevation changes derived from Pléiades sub-meter stereo images , 2014 .

[45]  Daene C. McKinney,et al.  A new remote hazard and risk assessment framework for glacial lakes in the Nepal Himalaya , 2016 .

[46]  J. Walder,et al.  Frequent outburst floods from South Tahoma Glacier, Mount Rainier, U.S.A.: relation to debris flows, meteorological origin and implications for subglacial hydrology , 1995, Journal of Glaciology.

[47]  Ian Joughin,et al.  An automated, open-source pipeline for mass production of digital elevation models (DEMs) from very-high-resolution commercial stereo satellite imagery , 2016 .

[48]  E. Berthier,et al.  Quantifying volume loss from ice cliffs on debris-covered glaciers using high-resolution terrestrial and aerial photogrammetry , 2016 .

[49]  Duncan J. Quincey,et al.  Contrasting geometric and dynamic evolution of lake and land-terminating glaciers in the central Himalaya , 2018 .

[50]  O. King,et al.  Spatial variability in mass loss of glaciers in the Everest region, central Himalayas, between 2000 and 2015 , 2016 .

[51]  J. Freer,et al.  Benchmarking observational uncertainties for hydrology: rainfall, river discharge and water quality , 2012 .

[52]  Ó. Knudsen,et al.  Controls on the development of supraglacial floodwater outlets during jökulhlaups , 2002 .

[53]  Evan S. Miles,et al.  Refined energy-balance modelling of a supraglacial pond, Langtang Khola, Nepal , 2016, Annals of Glaciology.

[54]  P. Chevallier,et al.  Remote sensing estimates of glacier mass balances in the Himachal Pradesh (Western Himalaya, India) , 2007 .

[55]  Daene C. McKinney,et al.  Brief communication: Observations of a glacier outburst flood from Lhotse Glacier, Everest area, Nepal , 2016 .

[56]  C. Scott Watson,et al.  The dynamics of supraglacial ponds in the Everest region, central Himalaya , 2016 .

[57]  M. R. Yoder,et al.  Geomorphic and geologic controls of geohazards induced by Nepal’s 2015 Gorkha earthquake , 2016, Science.

[58]  Koji Fujita,et al.  Role of supraglacial ponds in the ablation process of a debris-covered glacier in the Nepal Himalayas , 2000 .

[59]  Damodar Lamsal,et al.  Evaluating the growth characteristics of a glacial lake and its degree of danger of outburst flooding: Imja Glacier, Khumbu Himal, Nepal , 2009 .

[60]  T. Bolch,et al.  The Randolph Glacier inventory: a globally complete inventory of glaciers , 2014 .

[61]  M. Sharp,et al.  Seasonal changes in the morphology of the subglacial drainage system , 1998 .

[62]  E. Berthier,et al.  Decadal Region-Wide and Glacier-Wide Mass Balances Derived from Multi-Temporal ASTER Satellite Digital Elevation Models. Validation over the Mont-Blanc Area , 2016, Front. Earth Sci..

[63]  S. Garambois,et al.  Ground-penetrating radar and surface nuclear magnetic resonance monitoring of an englacial water-filled cavity in the polythermal glacier of Tete Rousse , 2016 .

[64]  Jeffrey S. Kargel,et al.  Climate Change and the Global Pattern of Moraine-Dammed Glacial Lake Outburst Floods , 2017 .

[65]  A. Kääb,et al.  Large drainages from short-lived glacial lakes in the Teskey Range, Tien Shan Mountains, Central Asia , 2017 .

[66]  Vena W. Chu,et al.  Greenland ice sheet hydrology , 2014 .