1. Transient simulations of the last 30,000 years, within the GENIE earth-system framework D.J. Lunt (1) M.Williamson (2) A. Price (3) P.J. Valdes (1)
What is GENIE?
Energy-balance-atmosphere transient coupled simulations
Fully-dynamic-atmosphere transient slab simulations
Conclusions and future work
(1) BRIDGE, School of Geographical Sciences, University of Bristol, UK
(2) ESM, School of Environmental Sciences, University of East Anglia, UK
(3) E-science centre, University of Southampton, UK

2. What is GENIE? Earth-system modelling framework
Focus on fast models – glacial/interglacial cycles
Modularity: plug-in / plug-out
Objective tuning
GRID computational resource

3. What is GENIE? IGCM EMBM ENTS Goldstein Slab More complex Atmosphere:
Prescribed
Land surface:
MOSES/
TRIFFID
ENTS
Seaice:
Goldstein
Slab
Ocean:
Ice-sheet :
GLIMMER (pdd)
Biogeochemistry:
BIOGEM
More complex

4. EMBM-GOLDSTEIN transient simulations
30,000 year transient simulation: 30kyrBP - present
Boundary conditions:
21kyrBP – present: ICE4G + ice-core CO2.
30kyrBP – 21kyrBP: linear interpolation using 30kyBP ice- sheet reconstruction (STAGE3 project).

5. EMBM-GOLDSTEIN transient simulations
Global mean surface temperature evolution.
‘Noise’ is due to integer ice-sheet mask (now fixed!).
Spinup approx 4000 years from 20oC isothermal ocean.

6. EMBM-GOLDSTEIN transient simulations
EMBM-GOLDSTEIN, SURFTEMP, LGM-MOD
HADSM3, SURFTEMP, LGM-MOD
EMBM-GOLDSTEIN : Global mean change, LGM-Pre-industrial = 4.1oC
HadSM3: = 3.8oC
EMBM shows good agreement with HadSM3, but has a much weaker response over seaice and Eurasian ice-sheet.

7. EMBM-GOLDSTEIN transient simulations
Temp, LGMtr-LGMeq
Transient
LGMeq
How close is the LGM to equilibrium, anyway?!
This implies – very! Good news for equilibrium simulations such as in

8. EMBM-GOLDSTEIN transient simulations
Greenland is too warm and too insensitive in this model.
Bolling-allerod warming is most significant departure from ‘fixed’ model prediction.
GISP2
Model
Model fix!

9. EMBM-GOLDSTEIN transient simulations
Warm periods after H2 and H1 and Younger Dryas are not reproduced in the model.
Model can aid with volume and duration of freshwater pulses of Heinrich events and duration of 8.2kyr event.\
GISP2
Model fix + hosing

10. IGCM-SLAB transient simulations
Initial atmosphere-only tuning experiment: Genetic algorithm, 30 tunable paramters, targets are modern (NCEP) surface heat fluxes.

11. IGCM-SLAB transient simulations
22,000 year simulation
2kyr LGM equilibrium spinup; 21kyrBP - 1kyBP transient.
Boundary conditions:
As for EMBM, but include orbital parameters.
Acceleration x10.
120 year calibration run for implied ocean heat fluxes.
Seaice flux limited to +-50Wm-2

12. IGCM-SLAB transient simulations
Variability seems quite constant, but be wary because of acceleration.
In a colder simulation (pre-tuning), more variability in glacial – due to seaice.

13. IGCM-SLAB transient simulations
EMBM-GOLDSTEIN, SURFTEMP, LGM-MOD
HADSM3, SURFTEMP, LGM-MOD
IGCM-SLAB, SURFTEMP, LGM-MOD
Global mean change, LGM-Pre-industrial:
EMBM-GOLDSTEIN = 4.1oC
HadSM3: = 3.8oC
IGCM-SLAB = 2.0oC
IGCM is in insensitive region of parameter space. Need to tune both modern and LGM. Seaice flux.

14. IGCM-SLAB transient simulations
Relatively insensitive to initial conditions. Need a larger ‘ensemble’!

15. IGCM-SLAB transient simulations
2 extra runs - constant pre-industrial and LGM atmospheric CO2.
Sensitivity of model to CO2 change from 195ppmv to 279ppmv is approx constant 0.75oC.

16. Conclusions EMBM-GOLDSTEIN has good ‘snapshot’ agreement with HadSM3.
LGM appears to be very close to equilibrium.
Transient simulation shows reasonable agreement with ice-core record but is insensitive over Greenland.
Model can be used to constrain volume/duration of freshwater pulses, but related warmings not simulated.
IGCM-SLAB has good agreement with modern climate (GA tuning)
Appears to have been over-tuned – LGM too warm relative to EMBM and HadSM3.
Sensitivity to CO2 forcing constant through glaciation.

17. Future Work
EMBM-GOLDSTEIN
Tune modern and LGM with EnKF. Non-ENTS version already tuned using this technique (for modern only).
Ensemble study of paleo-hosing experiments – compare with data.
Ensemble of accelerations.
IGCM-SLAB
Re-tune modern and LGM.
Compare to ice-core records.
Ensemble of physicical mechanisms (akin to CO2 presented here)
GENIE
Run identical deglaciation experiments with different versions – all tuned to the same targets.
Ice-sheet coupling (see poster Z024), TRIFFID/MOSES coupling, EVP sea-ice coupling, BIOGEM coupling.