HR: 17:30h
AN: G24A-07    [Abstracts]
TI: Constraints on Glacial Isostatic Adjustment (GIA) Motion in North American Using GPS
AU: * Sella, G F
EM: giovanni.sella@noaa.gov
AF: National Geodetic Survey, NOS-NOAA, 1315 East-West Hwy., Silver Spring, MD 20910 United States
AU: Stein, S
EM: stein@earth.northwestern.edu
AF: Geological Sciences, Northwestern University 1847 Sheridan Rd, Evanston, IL 60208 United States
AU: Dixon, T
EM: tdixon@rsmas.miami.edu
AF: MGG-RSMAS, University of Miami, 4600 Rickenbacker Csway., Miami, FL 33149 United States
AU: Craymer, M
EM: craymer@nrcan.gc.ca
AF: Geodetic Survey Canada, NRCan, 615 Booth Street, Ottawa, ON K1A 0E9 Canada
AU: James, T
EM: james@pgc.nrcan.gc.ca
AF: Geological Survey of Canada, NRCan, 9860 W. Saanich Rd., Sidney, BC V8L 4B2 Canada
AU: Mazzotti, S
EM: smazzotti@nrcan.gc.ca
AF: Geological Survey of Canada, NRCan, 9860 W. Saanich Rd., Sidney, BC V8L 4B2 Canada
AB: We use continuous and episodic Global Positioning System (GPS) data to measure the motion caused by glacial isostatic adjustment (GIA) due to glacial unloading in eastern North America. The large vertical signal due to GIA (>10mm/yr) in the area of maximum uplift, near Hudson Bay, permits this motion to be resolved with both continuous GPS (CGPS) data and even with episodic GPS (EGPS) data. We present data from 130 CGPS sites throughout North America and almost 100 EGPS sites of the Canadian Base Network (CBN). The CBN sites are located across central and southern Canada and have been episodically occupied between 1994 and 2002. We detect a coherent pattern of vertical motions around the area of maximum glacial loading, Hudson Bay. The observed velocities are initially large and upward, and decrease southward from Hudson Bay to zero, delineating the hinge line near the Great Lakes. The position of the hinge line is in agreement with some numerical GIA predictions. The horizontal residual velocities after removing the motion of the rigid North American plate also show a consistent, but more complex pattern than the vertical velocities. In particular we observe larger than expected motions on the east side of the Canadian Rocky Mountains, possibly reflecting larger ice loads and/or changes in mantle viscosity. We believe that this velocity field provides a comprehensive direct description of GIA motion and can be used to constrain GIA model predictions.
DE: 0700 CRYOSPHERE (4540)
DE: 1211 Non-tectonic deformation
DE: 1243 Space geodetic surveys
SC: Geodesy [G]
MN: Fall Meeting 2005