ICE-5G

ICE-5G
Name	ICE-5G
Type	Glacial isostatic adjustment model
Developer	Paul Huybrechts; Wouter van der Wal; James X. Mitrovica; Gerald A. Milne
First release	2000s
Latest release	2004
Language	English
Platform	Geophysical modelling frameworks

ICE-5G

ICE-5G is a widely cited glacial isostatic adjustment and paleoclimate reconstruction model that provides time-dependent ice-sheet reconstructions and sea-level predictions for the Late Pleistocene and Holocene. It integrates data from geodetic, geological, and geophysical investigations to produce maps and time series of ice thickness, sea-level change, and geoid variation that have been used across fields such as paleoclimatology, geodesy, and Quaternary geology. The model has informed debates about ice-sheet dynamics, mantle viscosity, and regional sea-level fingerprints in regions from Greenland to Antarctica and from Hudson Bay to Scandinavia.

Overview

ICE-5G is a synthesis product combining ice-sheet geometry, chronology, and loading histories to compute glacial isostatic adjustment and relative sea-level change using viscoelastic Earth models. It was developed during a period of active collaboration among researchers in Cambridge, Boston, Montreal, and Edinburgh, and it built on earlier reconstructions such as ICE-3G and ICE-4G while informing later efforts including reconstructions by the Peltier group and the Lambeck school. ICE-5G outputs include global grids of ice thickness, regional sea-level curves, and geoid perturbations intended for use in interpreting observations from tide gauges, coral records, and satellite missions like GRACE and TOPEX/Poseidon.

Development and Methodology

The development of ICE-5G combined empirical constraints from field studies with forward and inverse modelling of viscoelastic Earth response. Key methodological choices included selection of ice-margin chronologies based on radiocarbon and exposure-age datasets, adoption of mantle viscosity profiles consistent with postglacial rebound observations, and coupling to sea-level equations that account for self-gravitation and rotation effects. The work was conducted in collaboration among research groups associated with institutions such as the University of Toronto, Scripps Institution of Oceanography, University of Toronto Scarborough (noting individual affiliations), and benefited from comparisons with results from CMIP-era modelling and paleoceanographic syntheses like those produced by teams at Lamont–Doherty Earth Observatory and PAGES.

Data Sources and Inputs

ICE-5G integrates diverse empirical inputs: radiocarbon-calibrated chronologies from sites in Scotland, Ireland, Iceland, and Norway; cosmogenic nuclide exposure ages from Greenland and Alaska; marine limiting points from Fennoscandia and Svalbard; and tide-gauge and coral sea-level indicators from Bermuda, Tahiti, and Palmer Station. It used seismic and gravity constraints derived from studies near Hudson Bay and along the East Antarctic Ice Sheet margins, and incorporated ice-core stratigraphy and paleotemperature proxies from Vostok, EPICA, and GISP2 to harmonize glaciological timing. Geodetic datasets such as uplift rates measured by leveling and early GPS campaigns, and gravity observations from missions preceding GRACE, were also used to calibrate Earth rheology parameters.

Major Findings and Reconstructions

ICE-5G produced several influential reconstructions and conclusions: estimates of LGM ice volumes and regional ice-sheet extents including the Laurentide, Fennoscandian, and Cordilleran complexes; maps of postglacial rebound showing rapid uplift through regions such as Hudson Bay and parts of Scandinavia; predictions of spatially variable sea-level fingerprints affecting locations like Newfoundland and Iberia; and modeled geoid anomalies relevant to interpreting satellite gravity records. The reconstruction implied LGM eustatic sea-level fall consistent with coral and sedimentary constraints used by studies at Scripps and WHOI, and enabled reinterpretation of relative sea-level curves in basins studied by researchers at University of Bergen and Trinity College Dublin.

Applications and Impact

ICE-5G has been widely used in studies of glacial history, geodynamics, sea-level change, and ice-sheet modelling. It served as an input to investigations of present-day uplift measured by GPS networks, interpretations of GRACE gravity signals, and boundary conditions for ice-sheet numerical models developed at NASA, NSF-funded centers, and European laboratories. The model informed hazard assessments for coastal infrastructure in regions considered by planners in Netherlands and United Kingdom, and supported paleoceanographic syntheses by groups at NOAA and IHO. Its datasets were incorporated into interdisciplinary projects involving researchers from institutes such as USGS, Geological Survey of Canada, and university departments across Europe and North America.

Limitations and Uncertainties

ICE-5G embodies uncertainties stemming from sparse chronological control in certain regions, assumptions about ice rheology and basal conditions, and simplifications in Earth structure such as 1-D mantle viscosity profiles. Limitations include coarse spatial resolution for some peripheral ice masses, underconstrained chronologies in parts of Antarctica and Patagonia, and sensitivity to choices of sea-level equation parameters and rotational feedbacks. The model predates high-resolution datasets from later GRACE and dense GPS campaigns, and as such some regional predictions have been revised by studies at MIT, University of Toronto groups, and researchers affiliated with Utrecht University and University of Tasmania.

Related Models and Subsequent Versions

ICE-5G sits between earlier reconstructions (e.g., ICE-3G, ICE-4G) and later multi-disciplinary efforts such as ICE-6G and reconstructions produced by the Peltier group, the Lambeck group, and newer ensembles developed within the PAGES and CMIP communities. Subsequent versions incorporated improved geochronological datasets, three-dimensional Earth models, and assimilation of satellite gravimetry products from GRACE and GRACE-FO, and were compared with outputs from coupled ice-sheet–climate models run at facilities such as NERSC and ECMWF.

Category:Glaciology Category:Sea level