The Pine Island Glacier in West Antarctica is shrinking at a startling rate according to satellite observations. And the "hinge-point" of the glacier is retreating at 1.2 km per year according to Eric Rignot of the Jet Propulsion Laboratory in California. Geophysicists believe that the glacier is theoretically unstable and that the retreat could become irreversible. Many believe that such an event would be strong evidence for climatic change. Rignot cautions that the retreat he has observed might be a short-lived phenomenon, but adds it could still have implications for the stability of ice-sheets along the entire Antarctic coastline (Science 281 549).
Rignot used radar data taken between 1992 and 1996 by two European satellites, ERS-1 and ERS-2, to generate interference patterns that are sensitive to small vertical movements. These patterns provide information on the velocity of the ice – how fast it is creeping towards the bay – and the hinge point – the position on the glacier at which ice moves from resting on the bay bed to ice floating on the water. Recent measurements have suggested that the Pine Island glacier is melting at a much faster rate than other large ice shelves in the Antarctic. Researchers believed this was being caused by an influx of warm water from the Southern Pacific Ocean. Rignot’s latest work concludes that 76 ± 2 km3 of ice is being discharged into the bay each year, while only 71 ± 7 km3 is replenished from the Antarctic interior – which indicates that the glacier is shrinking at a startling rate. If this data does herald the start of collapse for the Antarctic ice sheet, water levels could rise by more than 5 m within a couple of centuries.
