HR: 11:50h
AN: C22A-07    [Abstracts]
TI: Tabular Icebergs in the South Atlantic: Melt Ponding, Melt Pond Geometry and Margin Evolution.
AU: * Sergienko, O V
EM: olga@uchicago.edu
AF: The Department of the Geophysical Sciences, The University of Chicago, 5734 S. Ellis Ave, Chicago, IL 60637 United States
AU: Scambos, T A
EM: teds@icehouse.colorado.edu
AF: National Snow and Ice Data Center, CIRES, University of Colorado, 1540 30th St., Boulder, CO 80309 United States
AU: MacAyeal, D R
EM: drm7@midway.uchicago.edu
AF: The Department of the Geophysical Sciences, The University of Chicago, 5734 S. Ellis Ave, Chicago, IL 60637 United States
AU: Fastook, J L
EM: fastook@maine.edu
AF: Department of Computer Science, University of Maine, 223 Neville Hall, Orono, ME 04469 United States
AB: In December of 2003, several massive icebergs originating from the Ronne-Filchner Ice Shelf in the souther Weddell Sea, Antarctica, arrived off the coast of South Georgia Island. MODIS (Moderate Resolution Imaging Spectroradiometer) imagery and photography obtained by astronauts aboard the international space station revealed that one of these icebergs was covered by and extensive meltwater pond. The main curiosity associated with the pond was its arrangement as elongate edge-parallel shallow water body about 1 km inboard from the iceberg edge. An "edge levee" appeared to keep this meltwater pond from spilling over the edge of the iceberg. ICESAT (Ice, Cloud, and Land Elevation Sattelite) profiles of this and "dry" icebergs of a similar size revealed surface elevation maxima near the iceberg edges that may represent the same kind of topographic expression that becomes the edge levees on the melt covered iceberg. Margin ridges seen in the ICESAT data were 1-2 m high and 400-1200 m wide. The one iceberg that displayed the levee-contained melt ponds disintegrated in late summer, 2003, in a pattern very similar to therapidbreak-up observed for the Larsen A and Larsen B ice shelves in 1995 and 2002, respectively. In this presentation, we shall consider the possible origins of this levee surface meltwater pond geometry. Among the hypotheses to be tested are: a. that the flexural effects of the iceberg in response to both the bending moment introduced at the iceberg edge by sea water pressure and the loading associated with surface melt ponding can explain the "edge levees", their size and location, and b. variable ice thickness, in particular thickening at the edges of the iceberg, is necessary to explain the "edge levees". The presentation will cover both the observational record of curious iceberg meltwater pond geometry and efforts to model iceberg flexural profiles using a simple approach involving the thin-elastic plate approximation. Where possible, model results will be compared to GLAS altimeter profiles of icebergs encountering strong surface melting.
DE: 9805 Instruments useful in three or more fields
DE: 4556 Sea level variations
DE: 1824 Geomorphology (1625)
DE: 1827 Glaciology (1863)
SC: Cryosphere [C]
MN: 2004 AGU Fall Meeting