A new model of the deglaciation history of Antarctica over the past 25 kyr has been developed, which we refer to herein as ICE-6G_C (VM5a).
This revision of its predecessor ICE-5G (VM2) has been constrained to fit all available geological and geodetic observations, consisting of: (1) the present day uplift rates at 42 sites estimated from GPS measurements, (2) ice thickness change at 62 locations estimated from exposure-age dating, (3) Holocene relative sea level histories from 12 locations estimated on the basis of radiocarbon dating and (4) age of the onset of marine sedimentation at nine locations along the Antarctic shelf also estimated on the basis of C dating.
2), the viscosity of the sublithospheric mantle as a function of depth (Fig. Errors in the knowledge of deglaciation history, the mantle viscosity profile, or lithospheric thickness may propagate into the inference of the other two parameters.
The assumption of lateral homogeneity of the viscoelastic structure may also introduce additional uncertainty. Plotted is Antarctica ice loss (right-hand side axis) and its contribution to global sea level rise (left-hand side axis) as a function of time.
In this study we aim to test the compatibility of this upper-mantle viscosity value of 0.5 × 10 Pa s with all available Antarctica GPS, ice thickness change, and RSL data.
(Herein we refer to the entire region from the base of the lithosphere to the seismic discontinuity at 660 km as the upper mantle.) We will find that this upper-mantle viscosity structure enables the model to fit all available Antarctica data, a finding that disagrees with a primary conclusion of Whitehouse Pa s on the basis of their analysis of the available RSL histories.
The space- and time-dependent ice thickness is adjusted in order to enable the model to best fit the inferred GPS uplift rates as well as the available ice thickness change data of Whitehouse (2012b) and assess the meaningfulness of the differences.
Thirdly, ice loss occurs quickly from 12 to 5 ka, and the contribution to global sea level rise during Meltwater Pulse 1B (11.5 ka) is large (5 m), consistent with sedimentation constraints from cores from the Antarctica ice shelf.
Fourthly, in ICE-6G_C there is no ice gain in the East Antarctica interior, as there is in W12A. Given for the RSL data (blue circles) is the present rate of RSL decrease in millimetres per year estimated from the youngest sea level marker data available at each site, which are 6–2 ka. Given for the RSL data (blue circles) is the present rate of RSL decrease in millimetres per year estimated from the youngest sea level marker data available at each site, which are 6–2 ka.
Velicogna & Wahr 2006; Peltier 2009; Shepherd , 2012).
In this study we will first employ GPS observations of vertical and horizontal crustal motion to estimate the velocities at 59 sites in Antarctica.