by Pascal Buri

Although considerable progress has been made in recent years in understanding the behaviour of debris-covered glaciers, many fundamental processes on, within and surrounding this glacier type remain ill-understood. As debris-covered glacier processes cross the fields of glaciology, geology, geomorphology, hydrology and meteorology in unique ways, a wide range of expertise is required to bridge our knowledge gaps. 

The session we organized for the AGU Fall Meeting in California in December 2019, co-organized by the Cryopshere and Earth and Planetary Surface Processes focus groups, aimed to improve process understanding related to debris-type glaciers and brought together expertise from quite different fields, e.g.:

• Jaako Putkonen (University of North Dakota, USA) found glacier ice in ice cores more than 1 million years old, protected from sublimation by a thick debris layer on a glacier in Ong Valley (Transantarctic Mountains, Antarctica).

• Leif Anderson (GFZ Potsdam, Germany) explored the causes of glacier thinning under debris by numerically modelling sub-debris melt, debris-transport and ice dynamics in 2D. The theoretical simulations showed that the zone of maximum glacier thinning propagates from upglacier into the debris-covered part of the glacier, suggesting that reduced ice flow from upglacier leads to increased glacier thinning under debris. James Ferguson (University of Zurich, Switzerland) used a similar approach in order to simulate numerically the behaviour of debris-covered Zmuttgletscher (Swiss Alps), which could be compared to a 150-year record of historical topographical data.

• Eric Petersen (University of Arizona, USA) showed how a debris-covered glacier can be a transitional state between a debris-free alpine glacier and a rock glacier, by using observational data from Galena Creek Rock Glacier (Wyoming, USA). 
• Alessandro Cicoira (University of Zurich, Switzerland) revealed the importance of water input for velocity-variations of rock glaciers in the Swiss Alps by using a numerical model with meteorological observations. 

Abstracts:

Leif Anderson (GFZ Potsdam, Germany) - Ice dynamical controls on the rapid thinning of debris-covered glaciers (Invited)

James Ferguson (U. Zurich, Switzerland) - Historical Reconstruction and Numerical Modelling of Zmuttgletscher, Swiss Alps, Since the Little Ice Age

Dawa Tshering Sherpa (Kathmandu U., Nepal) - Spatial Distribution of Debris Thickness from Remote-Sensing and Modeling in Marshyangdi River Basin, Nepal

Eric Petersen (U. Arizona, USA) - The Transition from Alpine Glacier to Rock Glacier: A Case Study at Sulphur Creek, Wyoming

Alessandro Cicoira (U. Zurich, Switzerland) - Resolving the influence of climatic forcing on rock glacier dynamics: a numerical modelling approach

Morgan Monz (U. of Minnesota Twin Cities, USA) - Crystallographic preferred orientation in warm, coarse-grained ice: a case study, Storglaciären, Sweden

Jaakko Putkonen (U. North Dakota, USA) - Ancient Ice Preserved Under A Meter-Thick Layer Of Debris; Ong Valley, Transantarctic Mountains, Antarctica

Emilio Mateo (Ohio State U., USA) - Evaluation of inter-annual to decadal changes in tropical Andean stream chemistry below debris-covered glaciers

Pascal Buri (U. Alaska Fairbanks, USA) - From the Equator to the Pole: How Latitude Affects Incident Shortwave Radiation on Supraglacial Ice Cliffs

Acknowledgements:

Thanks to the co-conveners of this session, Bob Anderson, Caroline Aubry-Wake and Jakob Steiner, for making this session happen, and to all the participants at our AGU session for great posters and exciting discussions across fields!