HR: 10:20h
AN: C12B-01 INVITED     [Abstracts]
TI: On the role of ice shelves on ice sheet mass balance
AU: * Rignot, E
EM: eric.rignot@jpl.nasa.gov
AF: Jet Propulsion Laboratory/Caltech, MS 300-319 4800 Oak Grove Drive, Pasadena, ca 91109-8099 United States
AB: The role of ice shelves in buttressing outflow from ice sheets into an ocean has remained a topic of controversy for several decades, mostly due to a lack of observations. With the collapse of Larsen A in 1995 and B in 2002, we observed the glacier response in more details than ever before. The results published by several authors revealed widespread acceleration, of surge type, with no return to the initial conditions. Dryglaski glacier is still accelerating in 2005 after speeding up by 300 percent. Evans/Hektoria/Green glaciers are slowing down but remain 500 percent out of balance. Crane glacier continues to accelerate with an ice front 10km upstream of its 1996 grounding line, but Leppard and Flask glaciers, which are still buttressed by an ice shelf, have remained steady. Ice shelf collapse has therefore a dramatic influence on glacier mass balance. Further south, Fleming Glaciers and others are 80 percent out of balance following the collapse of Wordie Ice Shelf in the 1980s, and maintaining steady speeds. Deep south, Pine Island Glacier accelerated 38 percent from 1974-2005, and its yearly acceleration rate increased fivefold. Thwaites is widening and could double its width if the eastern ice shelf cease to buttress its outflow as suggested by the appearance of new rifts at its grounding line between 1992 and 2005. Smith and Kohler glaciers, buttressed by Crosson/Dotson ice shelves are thinning rapidly and accelerated 10-50 percent in 1996-2005. The retreat/thinning is due to ice shelf thinning caused by a warmer ocean which triggered rapid grounding line retreat, reduction in buttressing force, and ice flow acceleration. A thinning ice shelf from a warmer ocean can therefore have a dramatic influence on ice sheet mass balance well before it breaks up. Add up sufficient atmospheric warming to produce melt water, and the ice shelves will collapse and precipitate the glaciers out of balance. The future of ice shelves will control the mass balance of the Antarctic Ice Sheet.
DE: 0720 Glaciers
DE: 0728 Ice shelves
DE: 0762 Mass balance (1218, 1223)
DE: 0776 Glaciology (1621, 1827, 1863)
DE: 1641 Sea level change (1222, 1225, 4556)
SC: Cryosphere [C]
MN: Fall Meeting 2005