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(1) BRIDGE, School of Geographical Sciences, University of Bristol, UK

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

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(1) BRIDGE, School of Geographical Sciences, University of Bristol, UK

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  1. Transient simulations of the last 30,000 years, within the GENIE earth-system frameworkD.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 http://www.genie.ac.uk

  3. What is GENIE? More complex

  4. EMBM-GOLDSTEINtransient 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-GOLDSTEINtransient 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-GOLDSTEINtransient 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-GOLDSTEINtransient 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-GOLDSTEINtransient 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-GOLDSTEINtransient 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-SLABtransient simulations Initial atmosphere-only tuning experiment: Genetic algorithm, 30 tunable paramters, targets are modern (NCEP) surface heat fluxes.

  11. IGCM-SLABtransient 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-SLABtransient 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-SLABtransient 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-SLABtransient simulations • Relatively insensitive to initial conditions. Need a larger ‘ensemble’!

  15. IGCM-SLABtransient 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. EMBM-GOLDSTEIN Future Work • 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.

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