Improved Constraints on Models of Glacial Isostatic Adjustment: A Review of the Contribution of Ground-Based Geodetic Observations

Abstract

The provision of accurate models of Glacial Isostatic Adjustment (GIA) is presently a priority need in climate studies, largely due to the potential of the Gravity Recovery and Climate Experiment (GRACE) data to be used to determine accurate and continent-wide assessments of ice mass change and hydrology. However, modelled GIA is 123Surv Geophys (2010) 31:465-507 DOI 10.1007/s10712-010-9100-4 uncertain due to insufficient constraints on our knowledge of past glacial changes and to large simplifications in the underlying Earth models. Consequently, we show differences between models that exceed several mm/year in terms of surface displacement for the two major ice sheets: Greenland and Antarctica. Geodetic measurements of surface displacement offer the potential for new constraints to be made on GIA models, especially when they are used to improve structural features of the Earth's interior as to allow for a more realistic reconstruction of the glaciation history. We present the distribution of presently available campaign and continuous geodetic measurements in Greenland and Antarctica and summarise surface velocities published to date, showing substantial disagreement between techniques and GIA models alike. We review the current state-of-the-art in ground-based geodesy (GPS, VLBI, DORIS, SLR) in determining accurate and precise surface velocities. In particular, we focus on known areas of need in GPS observation level models and the terrestrial reference frame in order to advance geodetic observation precision/accuracy toward 0.1 mm/year and therefore further constrain models of GIA and subsequent present-day ice mass change estimates.

Towards regional projections of twenty-first century sea-level change based on IPCC SRES scenarios

“…Recent efforts that will help to reduce the current GIA uncertainty include for instance the use of space-geodesy (e.g. King et al 2010). …”

A continuous velocity field for Norway

“…They showed that the effect of including or not including an annual signal in the time-series analysis, is much larger when a power-law plus white noise model is used instead of a pure white noise model. Teferle et al (2009) argue that annual and semi-annual signals can bias the velocity In King et al (2010) theoretical vertical site velocity uncertainties for stations in the Northern Hemisphere of 1.41, 1.58 and 0.54 mm/year after 5 years of observations and 0.71, 0.79, 0.27 mm/year after 10 years of observations are derived using DD, Precise Point Positioning (PPP) and regional stacking, respectively. The uncertainties in the horizontal components are between a third and a fourth in the Double Difference (DD) solution and between half and a third in the Precise Point Positioning (PPP) solution.…”

“…That is, systematical errors in the reference frame realization, errors in the GNSS analysis strategy or local secular motion of the antenna monument may also affect our velocity solutions (see e.g. King et al 2010;Wu et al 2011) and Appendix 7.1 for a more detailed discussion).…”

The earthquake deformation cycle

“…Observations of glacial isostatic adjustment (e.g. King et al, 2010) are hard to explain without having viscoelastic relaxation occurring at some depths within the earth, and lab experiments of rock properties also predict that viscoelastic relaxation mechanisms should be important for the deformation we see in the earthquake deformation cycle (Burgmann and Dresen, 2008).…”