1,1,1,3,5,7- 1Memorial University of Newfoundland, Dept. of Physics and Physical Oceanography, St. John's, Canada (lev@mun.ca)
- 2Dalhousie University, Halifax, Canada
- 3University of Manchester, Manchester, U.K.
- 4Defence Research & Development Canada, Medicine Hat, Canada
- 5University of Bergen, Bergen, Norway
- 6University of Ottawa, Ottawa, Canada
- 7Durham University, Durham, U.K.
GLAC3 is the first history matching of every last glacial cycle ice sheet. It therefore includes North American, Greenlandic, Icelandic,
Eurasian, Tibetan, Patagonian, and Antarctic components. Instead of determining a non-robust "optimal" chronology, history matching aims
to "bound reality" with robust assessment of both proxy data and model (both parametric and structural) uncertainties. For the four major ice
sheets, this entails Bayesian artificial neural network emulation of the glaciological model predictions to enable adequate Markov Chain
Monte Carlo sampling of chronologies. The history matching is against a large set of geophysical (such as relative sea level and marine
limit), geological (cosmogenic exposure and C14 ages), and glaciological (such as present-day ice surface velocity) constraints.
Aside from being a product of history matching, GLAC3 has two additional unique features. Firstly, it is the only available
deglacial, let alone full glacial cycle, global set of chronologies from glaciological modelling, using the Glacial Systems Model
(GSM) with hybrid shallow ice and shallow shelf ice dynamic. This enables physical resolution of ice sheets, ice streams, ice shelves,
and grounding line migration. As such, GLAC3 is subject to glaciological constraints such as borehole temperature profiles that
non-glaciological reconstructions can't resolve. Secondly, the glaciologically modelling is self-consistently coupled with full
visco-elastic glacio-isostatic adjustment enabling joint history matching of ice history and regional earth viscosity.
The presentation will focus on the relative phasing of each ice sheet, rates of mass gain and loss, and rates of ice margin migration. This
will be compared against both far-field relative sea level records as well as the results of fully coupled ice and climate modelling of the
last glacial cycle with LCice (LOVECLIM + GSM).
How to cite: Tarasov, L., Dalton, A., Dyke, A., Geng, M., Goffin, A., Hughes, A., Lecavalier, B., Mangerud, J., Milne, G., Svendsen, J.-I., and Woodroffe, S.: GLAC3 rates and phasing: the first joint history matching of global last glacial cycle ice sheet evolution and regional earth rheology, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-15518, https://doi.org/10.5194/egusphere-egu26-15518, 2026.
