North and northeast Greenland ice discharge from satellite radar interferometry

Science

Volumn 276, Issue 5314, 1997, Pages 934-937

  Rignot, E J ^a   Gogineni, S P ^b   Krabill, W B ^c   Ekholm, S ^d  

^a CALIFORNIA INSTITUTE OF TECHNOLOGY   (United States)

^b UNIVERSITY OF KANSAS   (United States)

^c NASA GODDARD SPACE FLIGHT CENTER   (United States)

^d Kort & Matrikelstyrelsen   (Denmark)

Author keywords

[No Author keywords available]

Indexed keywords

ICE;

ARTICLE; GEOLOGY; GREENLAND; IMAGE ANALYSIS; INTERFEROMETRY; PRIORITY JOURNAL; TELECOMMUNICATION;

BASAL MELTING; ICE DISCHARGE; ICE SHEET; MASS BALANCE; SEA LEVEL RISE;

GREENLAND;

EID: 0030620992     PISSN: 00368075     EISSN: None     Source Type: Journal    
DOI: 10.1126/science.276.5314.934     Document Type: Article

References (44)

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3. N. Reeh, in Quaternary Geology of Canada and Greenland, R. J. Fulton, Ed. (Geological Survey of Canada, Geology of Canada, 1989), chap. 14, pp. 793-822; C. S. Benson, U.S. Army Cold Reg. Res. Eng. Lab. Rep. 70 (Hanover, NH, 1962); A. Weidick, Gletscher-Hydrol. Medd. 85, (1985); H. Bader, U.S. Army Cold Reg. Res. Eng. Lab. Rep. I-B2 (Hanover, NH, 1961); F. Loewe, Beitr. Geophys. 46, 317 (1936).
4. N. Reeh, in Quaternary Geology of Canada and Greenland, R. J. Fulton, Ed. (Geological Survey of Canada, Geology of Canada, 1989), chap. 14, pp. 793-822; C. S. Benson, U.S. Army Cold Reg. Res. Eng. Lab. Rep. 70 (Hanover, NH, 1962); A. Weidick, Gletscher-Hydrol. Medd. 85, (1985); H. Bader, U.S. Army Cold Reg. Res. Eng. Lab. Rep. I-B2 (Hanover, NH, 1961); F. Loewe, Beitr. Geophys. 46, 317 (1936).
5. N. Reeh, in Quaternary Geology of Canada and Greenland, R. J. Fulton, Ed. (Geological Survey of Canada, Geology of Canada, 1989), chap. 14, pp. 793-822; C. S. Benson, U.S. Army Cold Reg. Res. Eng. Lab. Rep. 70 (Hanover, NH, 1962); A. Weidick, Gletscher-Hydrol. Medd. 85, (1985); H. Bader, U.S. Army Cold Reg. Res. Eng. Lab. Rep. I-B2 (Hanover, NH, 1961); F. Loewe, Beitr. Geophys. 46, 317 (1936).
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14. The grounding line may be located from an examination of small fractures at the surface of a glacier caused by the tidal displacements [S. N. Stephenson, Ann. Glaciol. 5, 165 (1984)], or using a radio echo sounder [ R. W. Jacobel, A. E. Robinson, R. A. Bindschadler, ibid. 20, 39 (1994)]. The limit of tidal flexing is precisely found with global positioning system (GPS) surveys and tiltmeters [ D. G. Vaughan, ibid., p. 372; A. M. Smith, J. Glaciol. 37, 51 (1991)]. The above techniques, however, are limited in spatial sampling. Visible imagery [ C. Swithinbank, K. Brunk, J. Sievers, Ann. Glaciol. 11, 150 (1988)] and radar altimetry [ R. H. Thomas, T. V. Martin, H. J. Zwally, ibid. 4, 283 (1983)] provide a large-scale, uniform sampling view of the grounding zone, but their precision is much less than that of GPS techniques.
15. The grounding line may be located from an examination of small fractures at the surface of a glacier caused by the tidal displacements [S. N. Stephenson, Ann. Glaciol. 5, 165 (1984)], or using a radio echo sounder [ R. W. Jacobel, A. E. Robinson, R. A. Bindschadler, ibid. 20, 39 (1994)]. The limit of tidal flexing is precisely found with global positioning system (GPS) surveys and tiltmeters [ D. G. Vaughan, ibid., p. 372; A. M. Smith, J. Glaciol. 37, 51 (1991)]. The above techniques, however, are limited in spatial sampling. Visible imagery [ C. Swithinbank, K. Brunk, J. Sievers, Ann. Glaciol. 11, 150 (1988)] and radar altimetry [ R. H. Thomas, T. V. Martin, H. J. Zwally, ibid. 4, 283 (1983)] provide a large-scale, uniform sampling view of the grounding zone, but their precision is much less than that of GPS techniques.
16. The grounding line may be located from an examination of small fractures at the surface of a glacier caused by the tidal displacements [S. N. Stephenson, Ann. Glaciol. 5, 165 (1984)], or using a radio echo sounder [ R. W. Jacobel, A. E. Robinson, R. A. Bindschadler, ibid. 20, 39 (1994)]. The limit of tidal flexing is precisely found with global positioning system (GPS) surveys and tiltmeters [ D. G. Vaughan, ibid., p. 372; A. M. Smith, J. Glaciol. 37, 51 (1991)]. The above techniques, however, are limited in spatial sampling. Visible imagery [ C. Swithinbank, K. Brunk, J. Sievers, Ann. Glaciol. 11, 150 (1988)] and radar altimetry [ R. H. Thomas, T. V. Martin, H. J. Zwally, ibid. 4, 283 (1983)] provide a large-scale, uniform sampling view of the grounding zone, but their precision is much less than that of GPS techniques.
17. The grounding line may be located from an examination of small fractures at the surface of a glacier caused by the tidal displacements [S. N. Stephenson, Ann. Glaciol. 5, 165 (1984)], or using a radio echo sounder [ R. W. Jacobel, A. E. Robinson, R. A. Bindschadler, ibid. 20, 39 (1994)]. The limit of tidal flexing is precisely found with global positioning system (GPS) surveys and tiltmeters [ D. G. Vaughan, ibid., p. 372; A. M. Smith, J. Glaciol. 37, 51 (1991)]. The above techniques, however, are limited in spatial sampling. Visible imagery [ C. Swithinbank, K. Brunk, J. Sievers, Ann. Glaciol. 11, 150 (1988)] and radar altimetry [ R. H. Thomas, T. V. Martin, H. J. Zwally, ibid. 4, 283 (1983)] provide a large-scale, uniform sampling view of the grounding zone, but their precision is much less than that of GPS techniques.
18. The grounding line may be located from an examination of small fractures at the surface of a glacier caused by the tidal displacements [S. N. Stephenson, Ann. Glaciol. 5, 165 (1984)], or using a radio echo sounder [ R. W. Jacobel, A. E. Robinson, R. A. Bindschadler, ibid. 20, 39 (1994)]. The limit of tidal flexing is precisely found with global positioning system (GPS) surveys and tiltmeters [ D. G. Vaughan, ibid., p. 372; A. M. Smith, J. Glaciol. 37, 51 (1991)]. The above techniques, however, are limited in spatial sampling. Visible imagery [ C. Swithinbank, K. Brunk, J. Sievers, Ann. Glaciol. 11, 150 (1988)] and radar altimetry [ R. H. Thomas, T. V. Martin, H. J. Zwally, ibid. 4, 283 (1983)] provide a large-scale, uniform sampling view of the grounding zone, but their precision is much less than that of GPS techniques.
19. The grounding line may be located from an examination of small fractures at the surface of a glacier caused by the tidal displacements [S. N. Stephenson, Ann. Glaciol. 5, 165 (1984)], or using a radio echo sounder [ R. W. Jacobel, A. E. Robinson, R. A. Bindschadler, ibid. 20, 39 (1994)]. The limit of tidal flexing is precisely found with global positioning system (GPS) surveys and tiltmeters [ D. G. Vaughan, ibid., p. 372; A. M. Smith, J. Glaciol. 37, 51 (1991)]. The above techniques, however, are limited in spatial sampling. Visible imagery [ C. Swithinbank, K. Brunk, J. Sievers, Ann. Glaciol. 11, 150 (1988)] and radar altimetry [ R. H. Thomas, T. V. Martin, H. J. Zwally, ibid. 4, 283 (1983)] provide a large-scale, uniform sampling view of the grounding zone, but their precision is much less than that of GPS techniques.
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22. To locate the grounding line with ERS radar interferometry, we used two interferograms formed by combining ERS image data acquired 1 day apart. A DEM was registered to each interferogram from a knowledge of the radar imaging geometry and the satellite precision orbits. The phase variations associated with surface topography and the interferometric baseline were then automatically removed from the interferograms, leaving only phase variations caused by the glacier deformation over 1 day. This deformation is the combination of a long-term motion under the driving stress procured by gravity, and a short-term vertical motion induced by tidal forcing from the ocean. If the glacier velocity (or gravity term) is continuous and steady throughout the period of observation, the differencing of two such interferograms produces a third interferogram which only contains the tidal signal. It is then possible to locate the limit of tidal flexing, or glacier hinge line, within less than 100 m, across the entire glacier width (10).
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44. We thank G. Duchossois, G. Kohlhammer, and the European Space Agency for providing radar data; R. H. Thomas for useful discussions; and C. Werner for providing a synthetic-aperture radar processor. This work was carried out at the Jet Propulsion Laboratory, California Institute of Technology, under a contract with NASA.