5. Key points 1) We use high resolution digital elevation models to document the evolution of supraglacial ice cliffs over one ablation season 2) Reclining cliffs that flatten, stable cliffs maintaining a self-similar geometry, and growing cliffs that expand laterally are observed 3) We develop a 3D-model of cliff backwasting driven by atmospheric melt, reburial by surrounding debris, and the effect of adjacent ponds Outlook: – Application at the glacier scale using satellite products – Simulation of multiple melt seasons

1- Institute of Environmental Engineering, ETH Zurich, Switzerland (*buri@ifu.baug.ethz.ch) 2- Scott Polar Research Institute, Trinity College, University of Cambridge, UK 3- Department of Physical Geography, Utrecht University, Netherlands 4- Department of Geography, Northumbria University, Newcastle upon Tyne, UK

P. BURI1*, E. S. MILES2, J. STEINER1,3, F. PELLICCIOTTI4,1

2nd INARCH Workshop Grenoble 17-19 October 2016

Physically-based modelling of ice cliff melt on a debris-covered glacier, Nepalese Himalayas

3. Methods – Models –

Static: distributed physically-based energy-balance model (Buri et al., 2016) - considers shading/fluxes from surrounding topography

Dynamic: 3D-backwasting model (based on static model) -monthly cliff geometry corrections based on melt -considers recovering by debris and exposure of ice

SCALE

2. Data – Cliff outlines–

Manually derived from UAV-orthoimage – Topography–

-UAV-DEMs (0.6m res.; Immerzeel et al., 2014) -ASTER (30m res.) for radiation modelling of far topography

– Meteorological input– AWS on Lirung Glacier (Ta, Ts, SW-rad., rH, wind sp. AWS off-glacier Kyanjing (LW-rad.)

References Buri, P., F. Pellicciotti, J. F. Steiner, E. S. Miles, and Immerzeel, W.W., 2016. A grid-based model of backwasting of supraglacial ice clis on debris-covered glaciers. Annals of Glaciology

Buri, P., E. S. Miles, J.F. Steiner, W.W. Immerzeel, P. Wagnon, and Pellicciotti, F., 2016. A physically-based 3D-model of ice cliff evolution over debris-covered glaciers. JGR (under review)

Han, H., Wang, J., Wei, J., and Liu, S., 2010. Backwasting rate on debris-covered Koxkar glacier, Tuomuer mountain, China. Journal of Glaciology

Immerzeel, W.W., Kraaijenbrink, P.D.A., Shea, J.M., Shresta, A.B., Pellicciotti, F., Bierkens, M.F.P. and de Jong, S.M., 2014. High-resolution monitoring of Himalayan glacier dynamics using unmanned aerial vehicles. Remote Sensing of Environment.

Østrem, G., 1959. Ice melting under a thin layer of moraine, and the existence of ice cores in moraine ridges. Geografiska Annaler,

Reid, T.D. and Brock, B.W., 2014. Assessing ice-cliff backwasting and its contribution to total ablation of debris-covered Miageglacier, Mont Blanc massif, Italy. Journal of Glaciology

Sakai, A., Nakawo, M. and Fujita, K., 1998. Melt rate of ice cliffs on the Lirung glacier, Nepal Himalayas, 1996. Bulletin of Glacier Research

Steiner, J.F., Pellicciotti, F., Buri, P., Miles, E.S., Immerzeel, W.W. and Reid, T.D. 2015. Modeling ice cliff backwasting on a debris covered glacier in the Nepalese Himalayas. Journal of Glaciology

Steiner, J.F. and Pellicciotti, F., 2016. Variability of air temperature over a debris-covered glacier in the Nepalese Himalaya. Annals of Glaciology

1. Introduction Debris cover reduces glacier melt through insulation (Østrem, 1959). Supraglacial cliffs are typical of debris-covered glaciers and may account for high mass losses by providing a direct ice-atmosphere interface. Their role has been investigated either in point scale studies of single cliffs (Sakai et al., 1998; Han et al., 2010, Reid & Brock, 2014, Steiner et al., 2015) or at the large-scale from satellite imagery, so that a gap in scale is evident. We suggested the first grid-based energy balance and ablation model for single cliffs, and demonstrated high variability in melt rates at the cliff scale (Buri et al., 2016). Building on that, we develop a dynamic 3D-backwasting model accounting for recovering/exposure of ice based on surrounding topography. Using this model approach we assess the importance of ice cliffs in terms of melt (Buri et al., under review).

2. Study site

May (observed) October

Modelled vs. observed cliff profiles:

Modelled vs. observed cliff outlines:

Modelled cliff melt:

4. Results