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Source: Breakup of the Larsen B Ice Shelf: 15 February 1998 - 18 March 1999
Please see the NSIDC Press Release, Antarctic Ice Shelf Disintegration Underscores a Warming World, for information about the 2008 break-up event.
NSIDC has monitored the Wikins ice shelf for signs of retreat for several years. A review of historical data and older satellite images indicates that retreat rate along the northern edge of the Wilkins began to pick up in the mid to late 1980's. In the last few years, several small break-up events have occurred, with long narrow icebergs calving from the shelf front and then becoming entrapped in thick sea ice in front of the shelf.
In March of 1998, AVHRR images recorded what appeared to be a large break-up event along the northwestern front. The shelf appearance changed from solid white to mottled in images of reflectance, from a uniformly cold temperature to a mixture of warm and cold surfaces in thermal imagery. Recently, SAR data gathered in August of 1998 was examined, and it revealed that this event was a major retreat of nearly 1100 km2.
Ordinarily, ice shelves calve relativly large bergs from their fronts; i.e., the majority of the area lost to maintain equilibrium is lost in a few major calving events. In the Larsen B, and as vividly illustrated here for the Wilkins, the retreating Peninsula ice shelves are calving thousands of bergs at once, suggesting that they are shattered in place before being dispersed by storms, currents, or wave action. A mechanism in which meltwater enhances ongoing, natural fracturing in the shelf was suggested many years ago by several scientists: current data supports the theory very well.
 AVHRR: 28 January 1996 |
 AVHRR: 20 November 1998 |
The breakups come as temperatures continue to rise and the melt season lengthens on both sides of the Antarctic Peninsula in the 1990's. Melt ponds are visible in other SAR images in the northeastern area of the Wilkins, and other field work by the British Antarctic Survey suggests that the snow on the shelf is saturated with water.
The lower image is an enhanced synthetic aperture radar (SAR) image acquired by Radarsat and provided by the Alaska Satellite Facility.
SAR Image: 16 August 1998
