HR: 17:45h
AN: G24A-08    [Abstracts]
TI: Glacial isostatic rebound, ongoing glacial wastage, and geoid change in southern Alaska.
AU: * Larsen, C F
EM: chris@giseis.alaska.edu
AF: Geophysical Institute University of Alaska, 903 Koyukuk Dr, Fairbanks, AK 99775 United States
AU: Motyka, R J
EM: roman.motyka@uas.alaska.edu
AF: Geophysical Institute University of Alaska, 903 Koyukuk Dr, Fairbanks, AK 99775 United States
AU: Freymueller, J T
EM: jeff@giseis.alaska.edu
AF: Geophysical Institute University of Alaska, 903 Koyukuk Dr, Fairbanks, AK 99775 United States
AU: Echelmeyer, K A
EM: kechel@gi.alaska.edu
AF: Geophysical Institute University of Alaska, 903 Koyukuk Dr, Fairbanks, AK 99775 United States
AU: Ivins, E R
EM: Erik.R.Ivins@jpl.nasa.gov
AF: Jet Propulsion Laboratory, California Institute of Technology, 4800 Oak Grove Dr., Pasadena, Ca 91109 United States
AB: Six years of GPS observations at 80 sites indicate crustal uplift rates from 10 to 32 mm/yr over a large area of southern Alaska. Rates of relative sea level (RSL) change at several tide gauges in the region are among the fastest anywhere, and indicate steady sea level fall over the past 100 yrs. Studies of raised shorelines at 32 sites throughout the region also show rapid RSL changes, up to 5.7 m over the last 250 yrs. Both the RSL and the GPS data show greatest uplift surrounding areas of post-Little Ice Age (LIA) deglaciation. Viscoelastic rebound models that invoke an Earth structure of a 50 km thick elastic crust over a 100 km thick asthenospheric layer with viscosity of 4 x 10**18 Pa s are capable of completely accounting for the rapid uplift observed by these three data types. Model predictions of associated rates of geoid change are up to 6 mm/yr, with the fastest rates found at centers of ongoing ice loss. Indeed, the model predictions of geoid changes in southern Alaska are dominated by ongoing ice wastage, with geoid changes due to viscoelastic rebound being a much smaller signal. Furthermore, the seasonal signal in the geoid due to annual glacier mass balance can be as much as an order of magnitude larger than the long term signal from ongoing glacier wastage. This effect is particularly large near the large, low elevation glacier termini bordering on the Gulf of Alaska where ablation rates can be as much as 12 to 14 m/yr WE.
DE: 1200 GEODESY AND GRAVITY
SC: Geodesy [G]
MN: Fall Meeting 2005