Rapid collapse of northern Larsen Ice Shelf, Antarctica

Science

Volumn 271, Issue 5250, 1996, Pages 788-792

  Rott, Helmut ^a   Skvarca, Pedro ^b   Nagler, Thomas ^a  

^a UNIVERSITY OF INNSBRUCK   (Austria)

^b INSTITUTO ANTÁRTICO ARGENTINO   (Argentina)

Author keywords

[No Author keywords available]

Indexed keywords

ATMOSPHERIC WARMING; BREAKUP; COLLAPSE; ERS-1; ICE SHELF; ICE SHELVES; RADAR IMAGES;

ANTARCTICA, LARSEN ICE SHELF;

EID: 0029768437     PISSN: 00368075     EISSN: None     Source Type: Journal    
DOI: 10.1126/science.271.5250.788     Document Type: Article

References (28)

1. C. Swithinbank, U S. Geol. Surv. Prof Pap. 1386-B (1988).
2. S. S. Jacobs, H H. Helmer, C. S. M. Doake, A. Jenkins, R. M. Frolich, J. Glaciol. 38, 375 (1992).
3. A. Jenkins and C. S. M. Doake, J. Geophys. Res 96, 791 (1991).
4. J. H. Mercer, Nature 271, 321 (1978).
5. C. S. M. Doake and D. G. Vaughan, ibid. 350, 328 (1991).
6. P. Skvarca, Ann Glaciol. 20, 6 (1994).
7. C. S. M. Doake, ibid. 3, 77 (1982).
8. P. Skvarca, ibid. 17, 317 (1993).
9. The ERS-1 SAR images were acquired at the German receiving station near the Chilean Antarctic Base O'Higgins, operating on a campaign basis The northern LIS was imaged by ERS-1 SAR in July 1992, between December 1992 and February 1993, in August 1993, and between mid-January and mid-February 1995 For comparison with conditions previous to the accelerated retreat, we analyzed Landsat Multispectral Scanner (MSS) images from 1 March 1986.
10. We obtained the ERS-1 SAR data in Universal Transverse Mercator projection based on the WGS-84 ellipsoid with nominal spatial resolution of 25 m by 25 m and location accuracy of better than 100 m in areas of low relief. We used geodetic field data to control and improve the absolute location accuracy. Geometric accuracy was high only close to sea level, because terrain-induced distortions resulting from radar imaging geometry could not be corrected because of a lack of high-resolution elevation data.
11. Data on ice motion, surface mass balance, and ice thickness were obtained for sections 1, 2, and 3 during field observations beginning in the early 1980s. Mean annual velocities from 1984 to 1994 in the center of the profiles (Fig. 2) were 385 m/year in section 1 and 248 m/year in section 3. Ice thicknesses at the same points were 250 m (section 1) and 220 m (section 3).
12. D A. Peel, in The Contribution of the Antarctic Peninsula to Sea Level Rise, E M. Morris, Ed. (British Antarctic Survey, Cambridge, 1992), pp. 11-15
13. W M Sackinger, M. O. Jeffries, H. Tippens, F Li, M. Lu, Ann. Glaciol 12, 152 (1989).
14. N. Contreras, unpublished data.
15. 2 was derived from an image of the Advanced Very High Resolution Radiometer (AVHRR) of the NOAA satellite with 1-km spatial resolution, acquired on 22 March 1995. An ERS-1 image from 11 February 1995, covering the area around Seal Nunataks, shows the southern ice boundary close to the position of 22 March.
16. Because of a lack of images, the exact date of the final opening of Prince Gustav Channel is not known.
17. T. Hughes, J Glaciol. 29, 98 (1983).
18. Surface mass balance was determined from measurements at stakes and snow pits. The specific mass balance is the change of mass per unit area within a given time period (the algebraic sum of accumulation and ablation). Mass balance for an entire glacier or ice shelf represents the overall change in mass.
19. The specific mass balance averaged over sites 15, 25, and 35 km south of Seal Nunataks revealed the following temporal changes: 1980 to 1988, 220 mm/ year; 1988 to 1991. 130 mm/year; and 1991 to 1994, -70 mm/year.
20. J C King, Int. J. Climatol. 14, 357 (1994).
21. J. A. J. Hofmann, in Actas, Primera Conferencia Latinoamericana sobre Geofisica, Geodesia e Investigación Especial Antárticas, Buenos Aires, 30 July to 3 August 1990, p. 160 (1991)
22. P. Skvarca, H. Rott, T. Nagler, Ann. Glaciol. 21, 291 (1995).
23. w are the density of ice and water, respectively, and W is the width of the ice shelf When the ice front retreated into the bay west of Sobral Peninsula, W became enlarged suddenly, violating the stability criterion (ii) The shear strain (∂u/∂y + ∂v/∂x) at a stable ice front is zero, where u is the velocity in direction x of the flow line and v is the velocity in direction y. This essentially means that the front is perpendicular to the flow lines. After 1986, the ice front north of Lindenberg Island differed increasingly from this stable geometry.
24. R. A. Bindschadler, M. A. Fahnestock, P. Skvarca, T. A. Scambos, Ann. Glaciol. 20, 319 (1994).
25. -2. For an undisturbed ice shelf of the size of the LIS, this force would be ∼0.1 to 0 2% of the stress due to shear at the side-walls. For the breakup of a heavily disturbed ice shelf, even these small forces due to wind may play a role, as may the effects of wind on ocean circulation. An increased probability of calving events during periods of persistent offshore winds and air temperatures above 0°C has been reported for Arctic ice shelves (M. O. Jeffries, Rev. Geophys. 30, 245 (1992)].
26. H. Rott, K. Sturm, H. Miller, Ann. Glaciol 17, 337 (1993), H. Rott and C Mätzler, ibid. 9, 195 (1987).
27. H. Rott, K. Sturm, H. Miller, Ann. Glaciol 17, 337 (1993), H. Rott and C Mätzler, ibid. 9, 195 (1987).
28. The ERS-1 SAR data (from ERS-1 Experiment AO1.A2 and ERS-1/ERS-2 Experiment AO2 A101) were provided by the European Space Agency. The temperature data from Marambio station were provided by Servicio Meteorológico Nacional, Fuerza Aerea Argentina. This work is a contribution to Austrian Science Fund (FWF) Project 10709-GEO, to the National Space Research Program of the Austrian Academy of Sciences, and to the Larsen Ice Shelf Project of Instituto Antártico Argentino, Direcciòn Nacional del Antártico.