The Ngozumpa Glacier Project


 
 

Glaciers in many parts of the Himalayas have undergone significant shrinkage in the last century in response to climatic warming, which in some areas is occurring faster than the global average. Some of this warming is part of a natural climatic cycle, although over the last 50 years or so probably about half of the warming is attributable to human sources (greenhouse gases). A particular problem associated with glacier shrinkage is the formation and catastrophic drainage of large moraine-dammed lakes, causing significant environmental hazards in many Himalayan valleys.  In recent decades, there have been several Glacier Lake Outburst Floods (GLOFs), which have caused widespread damage to homes, roads, bridges and industry, destruction of farmland, and loss of life. Many more potentially unstable lakes have been identified in populated regions, and some (such as Tsho Rolpa in the Rolwaling Himalaya, Nepal) are the subject of engineering projects to lower their levels and mitigate GLOF hazards. Mitigation works, however, are both expensive and logistically difficult in these unstable, high altitude environments.

In the Himalayas, large ice-contact lakes form in association with debris-covered glaciers, which behave differently to normal, clean glaciers. First, debris-covered glaciers deposit massive ridges of debris - moraines - around their snouts, which are capable of ponding large volumes of meltwater, but lack the mechanical strength to impound the water for more than a few decades.  Furthermore, by insulating ice from solar radiation and daily temperature fluctuations, a thick debris cover inhibits melting, thus delaying the response of the glacier to global warming. During periods of climatic warming, debris-covered glaciers slowly melt down, until closed hollows and lakes begin to form on the glacier surface. These lakes can rapidly expand and join up as icebergs break from the surrounding cliffs, so once lakes begin to form, the disintegration of the glacier and the formation of a large, potentially unstable lake can occur within a few years. It is as if the glaciers have ‘stored up’ their response to climate change, and are only now catching up with over a century of rising temperatures. It is possible that many large Himalayan valley glaciers are currently so far out of equilibrium with climate that they may cross the threshold into rapid lake growth in the coming decades even if the recent warming trend halts or reverses.

In the coming decades, potentially dangerous lakes are expected to form on many glaciers, and resources in Himalayan countries may be insufficient for the necessary mitigation works. There is therefore a growing need for a long term view of evolving glacier hazards in the region, based on a sound understanding of the life cycle of these glaciers, and their response to global warming.

The Ngozumpa Glacier Project aims to study the response of a large, debris-mantled glacier to climate change, and to obtain data which will allow the prediction and mitigation of potential hazards, especially lake outbursts and slope failures. This glacier is of particular interest because there are several supraglacial lakes on its ablation area, some of which are believed to lie close to the threshold for rapid lake growth. Additionally, the western lateral moraine of the glacier dams up a series of lakes in side valleys, which may be destabilised by glacier downwasting and moraine degradation.

The specific objectives of the research are to:


   Spillway Lake
 

Work has been conducted on the glacier in October 1998, April 1999, October - November 1999, October - November 2000, and September - November 2001, and annual or twice-annual research expeditions to the glacier will continue. Field research to date has focused on three main themes:

The Dynamics of Lake Growth
To date, detailed studies have been conducted on four supraglacial lakes, and repeat observations made of large parts of the glacier surface. Three of the lakes which have been studied in detail occupy "perched" basins on the glacier surface, that is, they are supported by glacier ice above the level of the water table within the glacier. During the study period, all of the lakes have undergone expansion. One of the lakes expanded very rapidly between October 1998 and October 1999, by a combination of subaerial melting, thermo-erosional melting at the waterline, and calving. The most efficient process of ice ablation was calving and subsequent melting of icebergs. Perched lakes, however, may be subject to rapid drainage (partial or total) if a connection is made to englacial conduits, thus limiting their lifespan. Abundant evidence of drained lakes can be seen on the glacier surface, in the form of silt-floored basins and cavities. Fortuitously, one of the study lakes drained during the monsoon of 2000,  allowing access to the former lake bed during September and October. It is clear that the lake had drained because calving around the lake margin exposed a meltwater conduit, thus connecting the lake with the englacial drainage system.

One of the studied lakes (Spillway Lake) does not occupy a perched basin, but overflows through the western lateral moraine of the glacier about 1 km from the terminus, and receives water from subaerial and subaqueous portals. Spillway Lake underwent only limited growth 1998 - 2001, except in areas of bare ice cliffs near the north-western and eastern margins. Growth of the lake was more rapid during 2000-2001 than in previous years. Additionally, widespread subsidence of the glacier surface to the north of the lake, due to the collapse of englacial conduits, has resulted in the formation of a chain of new lakes, which are expected to join up with Spillway Lake in the near future. Because the level of Spillway Lake is controlled by the altitude of the terminal moraine, it will experience continued growth unchecked by lake drainage unless the moraine dam itself is reduced in height or fails.

Energy Balance and Melting of the Glacier Surface
Predictive models of glacier behaviour require functions relating climatic inputs to glacier response (accumulation and ablation). Such functions are largely unknown for high altitude Himalayan glaciers, and are likely to be complex because of the influence of avalanching on accumulation and debris cover on ablation. Detailed studies of ice ablation beneath debris cover have been conducted at several sites on the glacier. The data have allowed the individual components of the surface energy balance of the glacier to be identified and quantified for selected study periods. During the autumn ablation period, incoming shortwave radiation provides over 90% of the energy for ablation, with surface albedo exerting an important modulating influence. In September 2001, sets of thermistors were installed within the debris layer, and results up to November 2001 are being analyised. The thermistor arrays were left in place, and combined with data from an automatic weather station installed on the glacier, will provide continuous records of energy fluxes to and through the debris layer.

An important new finding is that local variations in debris thickness across the glacier exert a strong control on overall melting rate. Uneven melting and topographic development are linked by a series of feedbacks, which transmit small-scale processes to large scale downwasting patterns. A numerical model of this process is currently under development.

Stable Isotope Analysis of Snow and Ice
The accumulation areas of the Ngozumpa Glacier extend up to over 8,000 metres and are guarded by highly unstable icefalls, hindering attempts to quantify inputs of snow and ice to the glacier. Insights into accumulation processes can, however, be gained through analysis of stable isotopes (O and H) in glacier ice in the ablation zone. The isotopic composition of glacier ice in the Himalayas varies with both altitude (5,000 - 8,000m in the Ngozumpa catchment) and season of snowfall (winter or monsoon). A large number of samples have been collected from the Ngozumpa and adjacent glaciers, which will allow the contribution of winter and monsoon snow to be identified within the ice stratigraphy, and possibly allow the relative importance of distinct snow accumulation areas to be determined.

Work planned for the 2002 autumn season includes continuation of the lake monitoring program and energy balance studies and Ground Penertrating Radar surveys of the glacier subsurface.


 

Personnel

Doug Benn                                                                             Project Leader
Richard Bates                                                                       Ground Penetrating Radar studies of subsurface ice structure
Charles Warren                                                                    Ice calving rates; lake evolution
Nick Hulton   (University of Edinburgh)                              Glacier modelling; GPR
Ross Purves    (University of Edinburgh)                              Energy balance modelling

Graduate students

Three PhD projects are being conducted as part of the Ngozumpa Glacier Project:

Seonaid Wiseman (BSc, Aberdeen):           The origin and life-cycle of supraglacial lakes
Kathryn Hands (BSc, Aberdeen):               The consequences of glacier downwasting: moraine degradation and supraglacial lake formation
Lindsey Nicholson (BSc, Edinburgh):        Ice ablation, isotope studies and energy-balance modelling
 

Associated Research


Reynolds Geo-Sciences                                Glacier hazard assessment and mitigation

Massimo Bollasina                                        Pyramid Group, Milan:    meterorology and climate change in the Khumbu Himal
Laura Bertolani
Gianni Tartari
 

Location Map



 

Publications: Himalaya


Benn, D.I., Wiseman, S. and Hands, K.A.  Growth and drainage of supraglacial lakes on the debris-mantled Ngozumpa Glacier, Khumbu Himal, Nepal. Journal of Glaciology, in press.

Benn, D.I. and Owen, L.A. Himalayan glacial sedimentary environments: a framework for reconstructing and dating former glacial extents in high mountain regions. Quaternary International, in press.

Owen, L.A., Gualtieri, L., Finkel, R.C., Caffee, M.W., Benn, D.I. and Sharma, M.M. Cosmogenic radionuclide dating of glacial landforms in the Lahul Himalaya, Northern India: constraining the timing of Late Quaternary glaciation. Journal of Quaternary Science, in press.

Benn, D.I., Wiseman, S. and Warren, C.R. 2000. Rapid growth of a supraglacial lake,   Ngozumpa Glacier, Khumbu Himal, Nepal. In: Debris-Covered Glaciers (Proceedings of a workshop held at Seattle, Washington, USA, September 2000) International Association of Hydrological Sciences, Publication 264, 177-185.

Benn, D.I. and Lehmkuhl, F. 2000. Mass balance and equilibrium-line altitudes of glaciers in high mountain environments. Quaternary International 65/66, 15-29.

Richards, B., Benn, D.I., Owen, L.A., Rhodes, E.J.  and Spencer, J.Q. 2000. Timing of late Quaternary glaciations south of Mount Everest in the Khumbu Himal, Nepal. Geological Society of America, Bulletin 112, 1621-1632.

Benn, D.I. and Owen, L.A. 1998. The role of the South Asian monsoon and the mid-latitude westerlies in controlling Himalayan glacial cycles: review and speculative discussion. Journal of the Geological Society, London, 155, 353-363.

Owen, L.A., Benn, D.I., Derbyshire, E., Evans, D.J.A., Mitchell, W., Sharma, M., Thompson,  D.M., Lloyd,  M. and Richardson,  S. 1995. The geomorphology and landscape evolution of the Lahul Himalaya, northern India.  Zeitschift fur Geomorphologie 39, 145-174.

Owen, L.A., Benn, D.I., E. Derbyshire, D.J.A. Evans, W. Mitchell, M. Sharma, D. Thompson, M. Lloyd, and S. Richardson. 1996. The Quaternary glacial history of the Lahul Himalaya, northern India. Journal of Quaternary Science 11, 25-42.
 

Other Recent Publications by Ngozumpa Glacier Project Members


Bates, C.R., Lynn, H. B. & Simon, M. 1999.  The study of a naturally fractured gas reservoir using seismic techniques. AAPG Bulletin, v 83, No. 9, p. 1392-1407.

Grimm, R. E., Lynn, H. B., Bates, C. R., Phillips, R., , Simon, K. M. and Beckham, W. 1999 Detection and Analysis of Naturally Fractured Gas Reservoirs: Multiazimuth seismic surveys in the Wind River Basin, Wyoming. Geophysics, v. 64, p. 1277-1292.

Bates, M.R., Bates, C.R., Gibbard, P.L., Macphail, R.I., Owen, F.J., Parfitt, S.A., Preece, R.C., Roberts, M.B., Robinson, J.E., Whittaker, J.Ee. and Wilkinson, K.N. 2000 Late Middle Pleistocene deposits at Norton Farm on the West Sussex Coastal Plain, Southern England. Journal of Quaternary Science, v. 15 (1), pp. 61-89.

Bates, C. R. and Phillips, D. 2000. Multi-component seismic surveying for near surface investigations: examples from central Wyoming and southern England. Journal of Applied Geophysics, v. 44 NO. 2-3, pp. 257-274.

Bates, M.R. and Bates, C.R., 2000. Multi-disciplinary approaches to the geoarchaeological evaluation of deeply stratified sedimentary sequences: examples from Pleistocene and Holocene deposits in Southern England, United Kingdom.  Journal of Archaeological Science, v. 27, no. 9, pp. 845-858.

Benn, D.I. 1996a. Subglacial and subaqueous processes near a glacier grounding line: sedimentological evidence from a former ice-dammed lake, Achnasheen, Scotland. Boreas 25, 23-36.

Benn, D.I. and Evans, D.J.A. 1996. The recognition and interpretation of subglacially-deformed materials. Quaternary Science Reviews 15, 23-52.

Ballantyne, C.K. and Benn, D.I. 1996. Paraglacial slope adjustment during recent deglaciation: implications for slope evolution in formerly glaciated terrain. In: Brooks, S. and Anderson, M.G. (Eds.) Advances in Hillslope Processes, Wiley, Chichester.

Benn, D.I. and Gemmell, A.M.D. 1997. Calculating equilibrium-line altitudes of former glaciers: a new computer spreadsheet. Glacial Geology and Geomorphology. http://ggg.qub.ac.uk/ggg/

Ringrose, T. and Benn, D.I. 1997. Confidence regions for fabric shape diagrams. Journal of Structural Geology 19, 1527-1536.

Evans, D.J.A., Rea, B.R. and Benn, D.I. 1999. Subglacial deformation and bedrock plucking in areas of hard bedrock. Glacial Geology and Geomorphology. http://ggg.qub.ac.uk/ggg/

Benn, D.I. and Clapperton, C.M. 2000a. Pleistocene glacitectonic landforms and sediments around central Magellan Strait, southernmost Chile: evidence for fast outlet glaciers with cold-based margins. Quaternary Science Reviews 19, 591-612.

Benn, D.I. and Clapperton, C.M. 2000b. Glacial sediment-landform associations and palaeoclimate during the last glaciation, Strait of Magellan, Chile. Quaternary Research 54, 13-23.

Benn, D.I. and Ringrose, T. Random variation of fabric eigenvalues: implications for the use of a-axis fabric data to differentiate till facies. Earth Surface Processes and Landforms, in press.

Benn, D.I. and Evans, D.J.A. 1998. Glaciers and Glaciation. Edward Arnold, London. 734 pp.

Boulton GS, Hulton NRJ and Vautravers M, 1995,  Ice-sheet models as tools for paleoclimatic analysis:  The example of the European ice sheet through the last glacial cycle.  Annals of Glaciology, 21, 103-110.

Hulton, N.R.J. and Mineter M.J., 2000, Modelling Self-Organisation in Ice Streams, Annals of Glaciology 30, pp127-136.

Hulton NRJ and Sugden DE, 1995  Modelling mass balance on former maritime ice caps:  a Patagonian example. Annals of Glaciology, 21, 304-310..

Hulton NRJ, Sugden DE Payne AJ  and Clapperton C,1994,  Glacier modelling and the climate of Patagonia during the last Glacial Maximum. Quaternary Research 42, 1-19.

Kirkbride, M.P. and C.R. Warren.  1997.  Calving processes at a grounded ice cliff.  Annals of Glaciology 24: 116 - 121.

Kirkbride, M.P. and C.R. Warren.  1999.  Tasman Glacier, New Zealand:  Twentieth-century thinning and predicted calving retreat. Global and Planetary Change 22(1-4): 11-28.

McCulloch, R. D., Bentley, M. J., Purves, R. S., Hulton, N.R.J., Sugden, D. E. and Clapperton, C. 2000. Climatic inferences from glacial and palaeoecological  evidence at the last glacial termination, southern South  America. Journal of Quaternary Science.15, 409-417.

Mineter MJ and Hulton NRJ, Parallel Processing for Finite Difference Modelling of Ice Sheets. Computers and Geosciences.  (In Press).

R.D. McCulloch, M.J. Bentley, R.S. Purves, D.E. Sugden., and C Clapperton and NRJ Hulton, 2000, Climatic inferences from glacial and palaeoecological evidence at the last glacial termination, southern South America, Journal of Quaternary Science 15,4, pp 409-418.

Purves RS and NRJ Hulton, 2000, Experiments in linking regional climate, ice sheet models and topographies, Journal of Quaternary Science pp369-376.

Purves, R.S. and Hulton, N.R.J. A Climatic-Scale Precipitation Model compared to the UKCIP baseline climate. International Journal of Climatology. (In press).

Purves, R.S. and Hulton, N.R.J. 2000. Experiments in linking climate, ice-sheet models and topography. Journal of Quaternary Science. 15, 369-375.

Purves, R. S., Mackaness, W. A., and Sugden, D. E. 1999, An Approach To Modelling The Impact Of   Snow Drift On Glaciation In The Cairngorm Mountains, Scotland: Journal of Quaternary Science, 14,  313-321.

Purves, R. S.,  and Sanderson, M. 1998. A methodology to allow avalanche forecasting on an information retrieval system,  Journal of Documentation. 54, 2, 198-209.

Purves, R., Mackaness, W.A., D. E. Sugden and J. Barton. 1999. The Application of GIS to the Modelling of Snow Drift. In B. M.  Gittings, (ed.), Innovations in GIS 6- Integrating Information Infrastructures with Geographical Information Technology, (Taylor and Francis, London), 243-254.

Purves, R. S., Barton, J. S., Mackaness, W.A. and Sugden, D. E. 1998. The development of a rule based spatial model of wind transport and deposition of snow. Annals of Glaciology, 26,  197-202.

Purves, R. S.,  Barton, J.S. and Wright, D.S.B. 1995. Automated measurements of snow temperature profiles in the Cairngorm mountains, Scotland. Meteorological Applications, 2, 199-207.

Sugden DE and Hulton NRJ, 1997,  Dynamics of Mountain ice caps during glacial cycles:  The case of Patagonia:  Annals of Glaciology 21, pp81-89.

Warren, C.R.  1999.  Calving speed in freshwater at Glaciar Ameghino, Patagonia.  Zeitschrift für Gletscherkunde und Glazialgeologie 35 (1): 21-34.

Warren, C.R. and M. Aniya.  1999.  The calving glaciers of southern South America.  Global and Planetary Change 22(1-4): 59-77.

Warren, C.R. and M.P. Kirkbride.  1998.  Temperature and bathymetry of ice-contact lakes in Mount Cook National Park, New Zealand.  New Zealand Journal of Geology and Geophysics 41: 133 - 143.

Warren, C.R., Benn, D.I., Winchester, V. and Harrison, S. 2001. Buoyancy-driven lacustrine calving, Glaciar Nef, Chilean Patagonia. Journal of Glaciology (in press)

Warren, C.R., N.F. Glasser, S. Harrison, V.Winchester, A.R.Kerr and A.Rivera.  1995.  Characteristics of tide-water calving at Glaciar San Rafael, Chile. Journal of  Glaciology, 41(138): 273 - 289.

Warren, C.R., D. Greene and N.F. Glasser.  1995.  Glaciar Upsala, Patagonia: Rapid calving retreat in fresh water.  Annals of Glaciology  21: 311 - 316.