GLOSSARY OF GLACIER MASS BALANCE AND RELATED TERMS Prepared by the Working Group on Mass-balance Terminology and Methods of the International Association of Cryospheric Sciences (IACS) IHP-VII Technical Documents in Hydrology No. 86 IACS Contribution No. 2 UNESCO, Paris, 2011 Published in 2011 by the International Hydrological Programme (IHP) of the United Nations Educational, Scientific and Cultural Organization (UNESCO) 1 rue Miollis, 75732 Paris Cedex 15, France IHP-VII Technical Documents in Hydrology No. 86 | IACS Contribution No. 2 UNESCO Working Series SC-2011/WS/4 © UNESCO/IHP 2011 The designations employed and the presentation of material throughout the publication do not imply the expression of any opinion whatsoever on the part of UNESCO concerning the legal status of any country, territory, city or of its authorities, or concerning the delimitation of its frontiers or boundaries. The author(s) is (are) responsible for the choice and the presentation of the facts contained in this book and for the opinions expressed therein, which are not necessarily those of UNESCO and do not commit the Organization. Citation: Cogley, J.G., R. Hock, L.A. Rasmussen, A.A. Arendt, A. Bauder, R.J. Braithwaite, P. Jansson, G. Kaser, M. Möller, L. Nicholson and M. Zemp, 2011, Glossary of Glacier Mass Balance and Related Terms, IHP-VII Technical Documents in Hydrology No. 86, IACS Contribution No. 2, UNESCO-IHP, Paris. Front-cover credits: Left: Snow pit on Storglaciären, Sweden (Peter Jansson). Middle: Hofsjökull, Iceland (809 km2), imaged on 13 August 2003 by the ASTER sensor on the NASA Terra spacecraft. Image acquired within the GLIMS initiative through the USGS/NAS EOS data gateway. Right: Grounded calving front of Store Gletscher, a western outlet of the Greenland Ice Sheet, August 2008 (Jason Box). Back-cover credits: Fritz Müller engaged in geodetic survey work, White Glacier, Axel Heiberg Island, Canada (Peter Adams). Publications in the series of IHP Technical Documents in Hydrology are available from: IHP Secretariat | UNESCO | Division of Water Sciences 1 rue Miollis, 75732 Paris Cedex 15, France Tel: +33 (0)1 45 68 40 01 | Fax: +33 (0)1 45 68 58 11 E-mail: [email protected] http://www.unesco.org/water/ihp/ Printed in UNESCO’s workshops Paris, France Stake for the measurement of accumulation on Vestfonna, Svalbard (Marco Möller). Note recently dislodged rime, and glaciation of vapour in wave crests in middle troposphere. Foreword This glossary, produced by a Working Group of the International Association of Cryospheric Sciences (IACS), is the first comprehensive update of glacier mass-balance terms for more than 40 years. The mass balance of a glacier is a measure of the change in mass of the glacier, or part of it, over a period of time. Mass-balance data help to explain why a particular glacier system may be advancing or retreating and what climate drivers (e.g. decreased snow accumulation; increased surface melt) are responsible for the changes. Fluctuations of the size (most typically length, but also area and/or surface elevation) are observed for several thousand of the well over 100,000 glaciers distributed globally from equatorial mountains to polar ice sheets. However regular annual mass-balance measurements are made on fewer than 200 glaciers. Mass-balance information is essential for defining the links between past, present and future climate changes and changes to glaciers in assessments such as those made by the Intergovernmental Panel on Climate Change (IPCC). Having a systematic, concise and unambiguous mass-balance terminology is a critical part of this. The first systematic attempts to define mass-balance terminology (UNESCO/IASH, 1970; Anonymous, 1969) were made during the United Nations Educational, Scientific and Cultural Organization (UNESCO) International Hydrological Decade (IHD, 1965-1974). The IHD programme provided an important impetus to international collaboration in hydrology and, in 1975, was succeeded by the UNESCO International Hydrological Programme (IHP). IHP has an emphasis on methodologies for hydrological studies, training and education in the water sciences and on the adaptation of the hydrological sciences to cope with the expected changing climate and environmental conditions. It is hence fitting that this glossary is published as part of the IHP series of Technical Documents in Hydrology. This publication is also a crucial early milestone in the work of the International Association of Cryospheric Sciences. IACS is the eighth and newest Association of the International Union of Geodesy and Geophysics (IUGG). Although it has precedents reaching back to the 1894 International Commission on Glaciers, IACS only became a full IUGG Association in 2007. This volume is the first work conceived and completed during the period that IACS has been a full Association. IACS is grateful to the International Hydrological Programme of UNESCO for providing the opportunity to publish the glossary as the second volume in a joint series. The mass-balance definitions and terminologies documented during the IHD have served well for more than 40 years. There are however some ambiguities in current usage, and new technologies (e.g. space-borne altimeters and gravimeters, ground penetrating radars, etc.) are now used for mass- balance measurements, particularly of ice sheets. This new glossary addresses these, promotes clarity, and provides a range of useful ancillary material. IACS, and the glaciological community as a whole, is very grateful to the Chair of the Working Group, Graham Cogley, and his dedicated team of volunteers for producing this volume. It is intended that the Working Group will continue to serve and to produce further reference publications on topics such as mass-balance measurement techniques and guidelines for reporting measurement uncertainty. Ian Allison President, International Association of Cryospheric Sciences Hobart, Australia January 2011 i Acknowledgements The Working Group is very grateful to Garry Clarke, Charles Fierz, Andrew Fountain, Will Harrison, Jo Jacka and Tomas Jóhannesson for careful reviews of the entire Glossary which led to substantial improvements. We also owe a great debt to those colleagues who have commented on the Glossary in whole or in part: Liss Andreassen and colleagues at Norges Vassdrags og Elektrisitetsvesen, Dave Bahr, Andrey Glazovskiy, Barry Goodison, Jon Ove Hagen, Matthias Huss, Wilfried Haeberli and Vladimir Konovalov. Many thanks also go to colleagues who have assisted in the compilation of the Glossary by discussing mass balance in general and advising on points of detail: Jason Amundsen, Richard Armstrong, Ed Bueler, Howard Conway, Hajo Eicken, Charles Fierz, Ralf Greve, Hilmar Gudmundsson, Jeff Kargel, Ian Joughin, Doug MacAyeal, Roman Motyka, Simon Ommanney, Tad Pfeffer, Bruce Raup, Gina Schmalzle, Ben Smith, Sergey Sokratov, Martin Truffer, Ed Waddington, Mauro Werder and Dale Winebrenner. Ken Moxham of the International Glaciological Society gave valuable advice about style. Eric Leinberger helped greatly by producing a professional-looking Figure 2 from our hand-drawn drafts. Sam Herreid generated the index. The advice of the colleagues named above, and possibly of others whose names we have inadvertently omitted, has improved the Glossary in ways that are many and substantial, and has brought it closer to the ideal of a community-wide consensus than would otherwise have been possible. Nevertheless we owe it to our advisors to note that the Working Group has not been able to agree with them on all points, and that any remaining mistakes are our own fault. We appreciate very much the willingness of UNESCO, through its International Hydrological Programme (IHP), to publish the Glossary of Glacier Mass Balance and Related Terms in its series Technical Documents in Hydrology and as IACS Contribution No. 2. Siegfried Demuth, chief of the IHP section on Hydrological Processes and Climate, and Vincent Leogardo of the IHP Secretariat, have been extremely helpful in seeing the Glossary through the process of publication. Last but not least, we are grateful to the Bureau of the International Association of Cryospheric Sciences (IACS) for its steady and enthusiastic support of the Working Group and the Glossary. ii IACS Working Group on Mass-balance Terminology and Methods Anthony Arendt Peter Jansson Geophysical Institute, Physical Geography and Quaternary Geology, University of Alaska, Stockholm University, Fairbanks, AK, Stockholm, USA Sweden [email protected] [email protected] Andreas Bauder Georg Kaser VAW, Institut für Meteorologie und Geophysik, Eidgenössische Technische Hochschule, University of Innsbruck, Zürich, Innsbruck, Switzerland Austria [email protected] [email protected] Roger Braithwaite Marco Möller Environment and Development, Physical Geography and Climatology, University of Manchester, RWTH Aachen University, Manchester, Aachen, UK Germany [email protected] [email protected] Graham Cogley (Chair) Lindsey Nicholson Geography, Institut für Meteorologie und Geophysik, Trent University, University of Innsbruck, Peterborough, Innsbruck, Canada Austria [email protected] [email protected] Regine Hock Al Rasmussen Geophysical Institute, Earth and Space Sciences, University of Alaska, University of Washington, Fairbanks, AK, Seattle, WA, USA USA [email protected] [email protected] Michael Zemp World Glacier Monitoring Service, University of Zürich, Zürich, Switzerland