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Terence J. Hughes
Although glaciology includes research on snow and ice of all kinds, most glaciological research is done on the large ice sheets of Antarctica and Greenland. Space limitations restrict this review to ice sheets — notably their mass balance, particularly in relation to "greenhouse" climate warming; their dynamic stability, particularly in relation to changing sea level; and climate records obtained by coring their ice. For a more complete account of glaciological research done or published in 2000, see the news bulletin ICE, numbers 122-124, and the Journal of Glaciology, volume 46, both published by the International Glaciological Society, Lensfield Road, Cambridge CB2 lER, United Kingdom.
Antarctic ice sheet
The major event at the ice sheet margin was Cruise 00-01 of R. V. Nathaniel B. Palmer to the Amundsen Sea. The icebreaker cruised past Ross Ice Shelf in March, days before the biggest known iceberg of the century was released. A few weeks later, similar large icebergs were released from Ronne Ice Shelf. These events have become common in the last two decades. Are they random concentrations of normal calving conditions or is new climatic and mechanical forcing in play? A possible climate link was the discovery that warm deep water was pouring over the continental shelf in the Amundsen Sea and flowing beneath Getz Ice Shelf and smaller ice shelves. Radarsat imagery showed these ice shelves to be heavily crevassed and perhaps on the verge of disintegrating. Swath bathymetry, seismic profiling and sediment coring revealed several large submarine troughs that crossed the continental shelf and had formerly been occupied by major ice streams that drained much of the West Antarctic ice sheet.
The major event on the ice sheet interior was the International Trans-Antarctic Scientific Expeditions (ITASE) traverse from Byrd Station (80 degrees South, 120 degrees West) to the Executive Committee Range. The American tractor-train traverse investigated several centuries of climate change recorded in ice cores, studied past and present meteorological conditions, and mapped the ice surface, internal ice stratigraphy, subglacial topography and glacial geology on nunataks.
A major publishing event was The West Antarctic Ice Sheet: Behavior and Environment, edited by Richard Alley and Robert Bindschadler, and published by the American Geophysical Union as part of its Antarctic Research Series. The book summarizes topics explored at a Chapman Conference at the University of Maine in 1998.
Each topic is treated by glaciologists and other scientists who have devoted many years to studying the stability of the West Antarctic ice sheet and its relationship to tectonic, oceanographic and climatic processes.
Other important Antarctic studies published in 2000 were of past climates, obtained from coring Siple Dome by scientists from the Universities of Wisconsin and Minnesota; a millennium-long record for flow of Ross Ice Shelf obtained from SAR and AVHRR satellite images by scientists from the University of Maryland, University of Colorado and the National Aeronautics and Space Administration (NASA); and dynamics of the Lambert Glacier/Amery Ice Shelf system studied by Australian scientists (see Journal of Glaciology, v. 46).
Greenland ice sheet
Robert H. Thomas and colleagues reported results of a NASA-sponsored study of the mass balance of the Greenland ice sheet and the stability of its ice streams. Ice input above and output across the 2,000-meter ice elevation contour line allowed ice thickening and thinning rates to be calculated for all sectors around the ice sheet. Some sectors were thickening and some were thinning. The last five kilometers of Kangerdlugssuaq Glacier has thinned 50 meters in the last five years. Glaciologists from NASA, the California Institute of Technology, and the universities of Bristol (United Kingdom), Ohio State, and Kansas used a digital elevation model and remote-sensing data to calculate mass-balance velocities for major ice streams draining North Greenland. A growing consensus among glaciologists is that the West Antarctic and Greenland ice sheets are unstable in important respects.
Hughes is a professor in the Department of Geological Sciences and Institute
for Quaternary and Climate Studies of the Bryand Global Sciences Center
at the University of Maine. His glaciological research has been in Antarctica
and Greenland, and he is the author of Ice Sheets (Oxford University Press,
1998).
E-mail: terry.hughes@maine.edu
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