Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | The Cryosphere Discuss., 6, 4305–4361, 2012 www.the-cryosphere-discuss.net/6/4305/2012/ The Cryosphere doi:10.5194/tcd-6-4305-2012 Discussions TCD © Author(s) 2012. CC Attribution 3.0 License. 6, 4305–4361, 2012 This discussion paper is/has been under review for the journal The Cryosphere (TC). Bedmap2: improved Please refer to the corresponding final paper in TC if available. ice bed, surface and thickness datasets Bedmap2: improved ice bed, surface and for Antarctica thickness datasets for Antarctica P. Fretwell et al. 1,* 1,* 1 2 1 P. Fretwell , H. D. Pritchard , D. G. Vaughan , J. L. Bamber , N. E. Barrand , Title Page R. Bell3, C. Bianchi4, R. G. Bingham5, D. D. Blankenship6, G. Casassa7, G. Catania6, D. Callens8, H. Conway9, A. J. Cook10, H. F. J. Corr1, D. Damaske11, Abstract Introduction V. Damm11, F. Ferraccioli1, R. Forsberg12, S. Fujita13, P. Gogineni14, Conclusions References J. A. Griggs2, R. C. A. Hindmarsh1, P. Holmlund15, J. W. Holt6, R. W. Jacobel16, 1 17 1 1 18 19 A. Jenkins , W. Jokat , T. Jordan , E. C. King , J. Kohler , W. Krabill , Tables Figures M. Riger-Kusk20, K. A. Langley21, G. Leitchenkov22, C. Leuschen14, 23 24 25 24 26 B. P. Luyendyk , K. Matsuoka , Y. Nogi , O. A. Nost , S. V. Popov , J I E. Rignot27, D. M. Rippin28, A. Riviera7, J. Roberts29, N. Ross30, M. J. Siegert2, A. M. Smith1, D. Steinhage19, M. Studinger31, B. Sun32, B. K. Tinto3, J I 17 6 32 33 B. C. Welch , D. A. Young , C. Xiangbin , and A. Zirizzotti Back Close 1 British Antarctic Survey, Cambridge, UK Full Screen / Esc 2School of Geographical Sciences, University of Bristol, UK 3Lamont-Doherty Earth Observatory of Columbia University, Palisades, USA Printer-friendly Version 4Istituto Nazionale di Geofisica e Vulcanologia, Rome, Italy 5 School of Geosciences, University of Aberdeen, UK Interactive Discussion 6Institute for Geophysics, University of Texas at Austin, USA 4305 Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | 7Centro de Estudios Cientificos, Santiago, Chile 8Laboratoire de Glaciologie, Universite´ Libre de Bruxelles, Brussels, Belgium TCD 9Earth and Space Sciences, University of Washington, Seattle, USA 6, 4305–4361, 2012 10Department of Geography, Swansea University, Swansea, UK 11Federal Institute for Geosciences and Natural Resources, Hannover, Germany 12National Space Institute, Technical University of Denmark, Denmark Bedmap2: improved 13National Institute of Polar Research, Tokyo, Japan ice bed, surface and 14Electrical Engineering & Computer Science, University of Kansas, Lawrence, USA thickness datasets 15 Stockholm University, Stockholm, Sweden for Antarctica 16St. Olaf College, Northfield, MN 55057, USA 17Alfred Wegener Institute, Bremerhaven, Germany P. Fretwell et al. 18Norwegian Polar Institute, Fram Centre, Tromsø, Norway 19NASA Wallops Flight Facility, Virginia, USA 20College of Science, University of Canterbury, Christchurch, New Zealand Title Page 21Department of Geosciences, University of Oslo, Norway Abstract Introduction 22Institute for Geology and Mineral Resources of the World Ocean, St.-Petersburg, Russia 23 Geology, University of California in Santa Barbera, USA Conclusions References 24Norwegian Polar Institute, Tromsø, Norway 25National Institute of Polar Research, Tokyo, Japan Tables Figures 26Polar Marine Geosurvey Expedition, St.-Petersburg, Russia 27 School of Physical Sciences, University of California, Irvine, USA J I 28Environment Department, University of York, Heslington, York, YO10 5DD, UK 29Department of Sustainability, Environment, Water, Population and Communities, Australian J I Antarctic Division, Hobart, Tasmania, Australia Back Close 30School of Geography, Politics and Sociology, Newcastle University, Newcastle upon Tyne, NE1 7RU, UK Full Screen / Esc 31Joint Center for Earth Systems Technology, NASA Goddard Space Flight Center, Greenbelt, USA Printer-friendly Version 32Polar Research Institute of China, Shanghai, China 33 Sez. Geofisica, Dip. Scienze Terra, Universita` di Milano, Italy Interactive Discussion *These authors contributed equally to this work. 4306 Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Received: 31 July 2012 – Accepted: 1 October – Published: 11 October 2012 Correspondence to: P. Fretwell ([email protected]) and H. D. Pritchard ([email protected]) TCD Published by Copernicus Publications on behalf of the European Geosciences Union. 6, 4305–4361, 2012 Bedmap2: improved ice bed, surface and thickness datasets for Antarctica P. Fretwell et al. Title Page Abstract Introduction Conclusions References Tables Figures J I J I Back Close Full Screen / Esc Printer-friendly Version Interactive Discussion 4307 Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Abstract TCD We present Bedmap2, a new suite of gridded products describing surface elevation, ice-thickness and the seafloor and subglacial bed elevation of the Antarctic south of 6, 4305–4361, 2012 60◦ S. We derived these products using data from a variety of sources, including many 5 substantial surveys completed since the original Bedmap compilation (Bedmap1) in Bedmap2: improved 2001. In particular, the Bedmap2 ice thickness grid is made from 25 million measure- ice bed, surface and ments, over two orders of magnitude more than were used in Bedmap1. In most parts thickness datasets of Antarctica the subglacial landscape is visible in much greater detail than was previ- for Antarctica ously available and the improved coverage of data has in many areas revealed the full 10 scale of mountain ranges, valleys, basins and troughs, only fragments of which were P. Fretwell et al. previously indicated in local surveys. The derived statistics for Bedmap2 show that the volume of ice contained in the Antarctic ice sheet (27 million km3) and its potential contribution to sea-level rise (58 m) are similar to those of Bedmap1, but the mean Title Page thickness of the ice sheet is 4.6 % greater, the mean depth of the bed beneath the Abstract Introduction 15 grounded ice sheet is 72 m lower and the area of ice sheet grounded on bed below sea level is increased by 10 %. The Bedmap2 compilation highlights several areas beneath Conclusions References the ice sheet where the bed elevation is substantially lower than the deepest bed indi- Tables Figures cated by Bedmap1. These products, along with grids of data coverage and uncertainty, provide new opportunities for detailed modelling of the past and future evolution of the J I 20 Antarctic ice sheets. J I 1 Introduction Back Close It is more than a decade since grids of ice-surface elevation, ice thickness and sub- Full Screen / Esc glacial topography for Antarctica were presented by the BEDMAP Consortium as dig- ital products (hereafter we refer to these products collectively as Bedmap1, Lythe Printer-friendly Version 25 et al., 2001), and as a printed map (Lythe et al., 2000). Since then, Bedmap1 products have been widely used in a variety of scientific applications, ranging from geological Interactive Discussion 4308 Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | (e.g. Jamieson et al., 2005) and glaciological modelling (e.g. Wu and Jezek, 2004), to support for geophysical data interpretation (e.g. Riedel et al., 2012), as a basis for TCD tectonic interpretation (e.g. Eagles et al., 2009), as a baseline for comparison of newly- 6, 4305–4361, 2012 acquired subglacial information (e.g. Welch and Jacobel, 2003), and even to help im- 5 prove understanding of the distribution of marine species (Vaughan et al., 2011). Like their predecessors (e.g. Drewry and Jordan, 1983), Bedmap1 products were Bedmap2: improved based on a compilation of data collected by a large number of researchers using a va- ice bed, surface and riety of techniques, with the aim of representing a snap-shot of understanding, and as thickness datasets such, Bedmap1 has provided a valuable resource for more than a decade. However, in for Antarctica 10 recent years, inconsistencies (such as negative water column thickness beneath some ice-shelf areas) in Bedmap1 have proved to be limitations and several new versions P. Fretwell et al. have been developed (e.g. Le Brocq et al., 2010; Timmerman et al., 2010), which have proved very useful to the community. Since Bedmap1 was completed, a substantial Title Page quantity of ice-thickness and subglacial and seabed topographic data has been ac- 15 quired by researchers from many nations. The major improvement in coverage and Abstract Introduction precision that could be achieved by incorporating these data into a single new compila- tion is obvious. Here we present such a compilation, Bedmap2, which maintains several Conclusions References useful features of Bedmap1, but provides many improvements; higher resolution, or- Tables Figures ders of magnitudes increase in data volume, improved data coverage and precision; 20 improved GIS techniques employed in the gridding; better quality assurance of input J I data; a more thorough mapping of uncertainties; and finally fewer inconsistencies in the gridded products. J I General philosophy of approach Back Close Full Screen / Esc The general approach used to derive the Bedmap2 products was to incorporate all 25 available data, both geophysical and cartographic, and in particular, we endeavoured to include all measurements available to date. However, it should be noted that the Printer-friendly Version disparities between varied input data sources, the