HR: 1340h
AN: G33A-0019    [Abstracts]
TI: Post-glacial rebound in North America: ice load parameters from an NA inversion
AU: Piana Agostinet, N
EM: piana@ingv.it
AF: Istituto Nazionale di Geofisica e Vulcanologia, Via di Vigna Murata 605, Rome, RM 00143 Italy
AU: * Giunchi, C
EM: giunchi@ingv.it
AF: Istituto Nazionale di Geofisica e Vulcanologia, Via di Vigna Murata 605, Rome, RM 00143 Italy
AU: Spada, G
EM: spada@fis.uniurb.it
AF: Istituto di Fisica, Universitá di Urbino, Via Santa Chiara 27, Urbino, PU 61029 Italy
AU: Cianetti, S
EM: cianetti@ingv.it
AF: Istituto Nazionale di Geofisica e Vulcanologia, Via di Vigna Murata 605, Rome, RM 00143 Italy
AB: The influence of ice load evolution on glacial isostatic adjustment (GIA) has been widely recognized. In the past decades, inference of ice load parameters has often been derived from surface geophysical observables (e.g. relative sea-level, RSL, curves) associated with the post-glacial deformation of the Earth. Geophysical inversion techniques have been used to constrain ice time-history and to examine the link between data-sets and geophysical models. These models require an ice-load model, mostly based on geological andglaciological evidence, and a rheological model which defines the viscosity profile for the Earth's mantle. Here, we solve the problem of the determination of the ice load parameters inverting RSL and VLBI data by a non-linear, global directed, technique based on the Neighbourhood Algorithm (NA)(Sambridge, 1998). We introduce a new ice load model for the Laurentide ice sheet which consists of seven different parabolic ice domes covering the area of the North America. Isochrons for ice retreat as well as the ice thickness at the center of each dome are assumed a priori as in the ICE3G model by Tushingham and Peltier (1991). An ice-sheet scaling parameter is introduced for each element of the ice aggregate and the NA inversion technique is applied to constrain these scaling factors using 131 RSL time-series and 45 VLBI baselines deformation rates as data-set of observations. RSL synthetic predictions are computed solving the sea-level equation for a viscoelastic spherically symmetric incompressible Earth according to the formulation presented by Farrel and Clark (1976) in which the eustatic, the glacio-isostatic and the hydro-isostatic terms are taken into account and the fixed-shorelines approximation is adopted. The viscosity profile is the same as Tushingham and Peltier (1991). Compared with the ICE3G model, our preferred North America glacier shows (1) a significant and sizable reduction of the load thickness over most of the ice-covered region and (2) a relatively slow increase of the ice thickness with distance from its margin in the Hudson Bay region.
DE: 0726 Ice sheets
DE: 1236 Rheology of the lithosphere and mantle (7218, 8160)
SC: Geodesy [G]
MN: Fall Meeting 2005