1. A Preliminary Calibrated Deglaciation Chronology for the Eurasian Ice Complex
Lev Tarasov and W.R. Peltier
Memorial University of Newfoundland/ University of Toronto

2. Inferred Greenland temperature

3. Glacial modelling challenges and issues: What's missing in pure geophysical reconstructions

4. Glacial Systems Model (GSM)
3D thermo-mechanically coupled ice-sheet model, 0.5 * 1.0 (lat/long) model resolution
VM2 viscosity model
detailed surface mass-balance and ice-calving modules
global gravitationally self-consistent RSL solver
fully coupled surface drainage solver

5. Climate forcing
Last Glacial Maximum (LGM) precipitation and temperature from 4 (6 for N. A.) highest resolution Paleo Model Intercomparison Project GCM runs
Mean and EOF fields
Present day observed fields

6. Climate forcing time-dependence

7. Lots of ensemble parameters
3(5 for North America) ice dynamical
13(16) regional precipitation
LGM precipitation EOFs most significant for North America
4 ice calving
4 temperature
4(2) ice margins
1 model version
= 29 (32)

8. Need constraints -> DATA

9. Initial European deglacial margin chronology (Saarnisto and Lunkka, 2003)
margin forcing: surface mass-balance near ice margin adjusted to fit chronology
applied up to km buffer zone

10. New margin chronology (Svendsen et al, per. comm., Oct/06)

11. RSL site weighting (U of T RSL database)

12. Noisy data and non-linear system => need calibration and error bars

13. Bayesian calibration
Sample over posterior probability distribution for the ensemble parameters given fits to observational data using Markov Chain Monte Carlo (MCMC) methods
Other constraint:
Minimize margin forcing

14. Large ensemble Bayesian calibration
Bayesian neural network integrates over weight space
Self-regularized
Can handle local minima
O(1 million) model sampling

15. Overall best RSL fitting models
Black: new margin
Red: old margin
Problem with south-western Norway

16. Mean ensemble LGM ice thickness

17. ICE-5G LGM thickness

18. LGM: Ensemble mean - ICE-5G

19. 1 sigma range for LGM ice thickness

20. Ensemble mean present-day rate of uplift

21. 1 sigma range of ensemble rate of uplift

22. Deglacial eustatic sea-level chronology

23. Summary European contributions: LGM: 19.5 +- 1.5 m eustatic
mwp1-a: m eustatic ( m old margin)
Strong dependence on margin chronology
likely problems with south-western margin chronology for Fennoscandia
physical model + calibration against data => meaningful error bars/probability distributions
Significant differences with ICE-5G => CAN'T IGNORE CLIMATE and ICE DYNAMICS

24. Key points to walk away with
GSM + calibration = data and physics integration
There's more to ice than just post-glacial rebound, RSL, and mantle viscosity