SPIRIT. SPOT 5 stereoscopic survey of Polar Ice: Reference Images and Topographies during the fourth International Polar Year (2007–2009) |
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| Authors: | Jérôme Korona Etienne Berthier Marc Bernard Frédérique Rémy Eric Thouvenot |
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| Institution: | 1. University of Washington, Applied Physics Laboratory, Polar Science Center, United States of America;2. Scripps Institution of Oceanography, University of California, San Diego, United States of America;3. Department of Earth and Space Sciences, University of Washington, United States of America;4. Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA 91109, United States of America;5. Cryospheric Science Lab, NASA Goddard Space Flight Center, Greenbelt, MD 20771, United States of America;6. Earth System Science Interdisciplinary Center, University of Maryland, College Park, MD 20740, United States of America;7. Department of Geological Sciences, University at Buffalo, Buffalo, NY 14260, United States of America;8. SGT, Inc/KBR Wyle;9. Department of Geophysics, Colorado School of Mines, Golden, CO 80401, United States of America;1. State Key Laboratory of Remote Sensing Science, Institute of Remote Sensing and Digital Earth, Chinese Academy of Sciences, Beijing 100101, China;2. Department of Geographical Sciences, University of Maryland, College Park, MD 20742, USA;3. Code 618, Biospheric Sciences Branch, NASA/Goddard Space Flight Center, Greenbelt, MD 20771, USA;4. Institute of Forest Resource Information Technique, Chinese Academy of Forestry, Beijing 100091, China;5. Institute of Photogrammetry and Cartography, Technische Universitaet Muenchen Arcisstr. 21, Munich D-80333, Germany |
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| Abstract: | Monitoring the evolution of polar glaciers, ice caps and ice streams is of utmost importance because they constitute a good indicator of global climate change and contribute significantly to ongoing sea level rise. Accurate topographic surveys are particularly relevant as they reflect the geometric evolution of ice masses. Unfortunately, the precision and/or spatial coverage of current satellite missions (radar altimetry, ICESat) or field surveys are generally insufficient. Improving our knowledge of the topography of Polar Regions is the goal of the SPIRIT (SPOT 5 stereoscopic survey of Polar Ice: Reference Images and Topographies) international polar year (IPY) project. SPIRIT will allow (1) the acquisition of a large archive of SPOT 5 stereoscopic images covering most polar ice masses and, (2) the delivery of digital terrain models (DTM) to the scientific community.Here, we present the architecture of this project and the coverage achieved over northern and southern polar areas during the first year of IPY (July 2007 to April 2008). We also provide the first accuracy assessments of the SPIRIT DTMs. Over Jakobshavn Isbrae (West Greenland), SPIRIT elevations are within ±6 m of ICESat elevations for 90% of the data. Some comparisons with ICESat profiles over Devon ice cap (Canada), St Elias Mountains (Alaska) and west Svalbard confirm the good overall quality of the SPIRIT DTMs although large errors are observed in the flat accumulation area of Devon ice cap. We then demonstrate the potential of SPIRIT DTMs for mapping glacier elevation changes. The comparison of summer-2007 SPIRIT DTMs with October-2003 ICESat profiles shows that the thinning of Jakobshavn Isbrae (by 30–40 m in 4 years) is restricted to the fast glacier trunk. The thinning of the coastal part of the ice stream (by over 100 m) and the retreat of its calving front (by up to 10 km) are clearly depicted by comparing the SPIRIT DTM to an ASTER April-2003 DTM. |
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