Design for the Last Deglaciation experiment

You will find on this page information about the experiment design for the PMIP4 Last Deglaciation experiments. Please make sure to read the Associated publications before setting up your experiments or using the output data, and read any how-to sections associated with specific boundary conditions. Get in touch with the following people if you have questions: Jean-Yves Peterschmitt Technical questions or missing data Ruza Ivanovic working group leader Lauren Gregoire working group co-leader Masa Kageyama working group steering Didier Roche working group steering Paul Valdes working group steering Andrea Burke working group steering

Associated publications

Last deglaciation experiment design, version 1:
Ivanovic, R. F.; Gregoire, L. J.; Kageyama, M.; Roche, D. M.; Valdes, P. J.; Burke, A.; Drummond, R.; Peltier, W. R. and Tarasov, L.: Transient climate simulations of the deglaciation 21–9 thousand years before present, version 1; PMIP4 Core experiment design and boundary conditions, Geosci. Model Dev., 9, 2563–2587, doi:10.5194/gmd-9-2563-2016, 2016.

Version 1 Specifications

For general advice on boundary condition implementation in palaeoclimate models, see Kageyama et al. (2016).

Last Glacial Maximum spinup (21 ka)

This spinup simulation is compatible with the PMIP4-CMIP6 LGM experiment, which can also be used as the initialisation state for the fully transient run from 21 ka onwards, provided the ICE-6G_C or GLAC-1D ice sheet reconstructions and associated boundary conditions (orography, coastlines and bathymetry) were used.

PMIP4 specifications
PMIP4 name	LDv1-LGMspin
Astronomical parameters	eccentricity = 0.018994 obliquity = 22.949° perihelion-180° = 114.42° Date of vernal equinox : Noon, 21st March
Solar constant	1361.0 ± 0.51365 W m-2
Trace gases	CO2 = 190 ppm CH4 = 375 ppb N2O = 200 ppb CFC = 0 O3 = Preindustrial (e.g. 10 DU)
Ice sheets, orography and coastlines	21 ka data from either - ICE-6G_C reconstruction: [ Access to data ] - GLAC-1D reconstruction: [ Access to data ]
Bathymetry	Keep consistent with the coastlines, using either: - Data associated with the ice sheet - Preindustrial bathymetry
Global ocean salinity	+ 1 psu, relative to preindustrial
All others	As per the PMIP4-CMIP6 LGM experiment

Transient orbit and trace gases spinup (26-21 ka)

This option for spinning-up the last deglaciation simulation uses transient orbital parameters and trace gases from 26-21 ka.

PMIP4 specifications
PMIP4 name	LDv1-transpin
Astronomical parameters	All orbital parameters should be transient as per Berger (1978) 26-21 ka [ Access to data & README ! ]
Trace gases	All adjusted to the AICC2012 chronology Veres et al. (2013) 26-21 ka: CO2 = Transient, as per Bereiter et al. (2015): [ Access to data (md5sum = c54a033d8cbf588bc2b95d3b92ff9b1c) ] CH4 = Transient, as per Loulergue et al. (2008): [ Access to data ] N2O = Transient, as per Schilt et al. (2010): [ Access to data ]
All others	As per the LGM (21 ka) spinup type; LDv1-LGMspin

Transient deglaciation (21-0 ka)

These are the specifications for the full transient run 21-0 ka.
(Note, the period of focus for version 1 of the experiment is 21-9 ka, but all boundary conditions are provided until 0 ka so that groups can extend the run to present if they wish).

PMIP4 specifications
PMIP4 name	LDv1
Initial conditions (pre 21 ka)	Recommended (optional) to use either: - LDv1-LGMspin - LDv1-transpin See above for details. The method must be documented, including information on the state of spinup
Astronomical parameters	Transient, as per Berger (1978) [ Access to data & README ! ]
Solar constant	1361.0 ± 0.51365 W m-2
Trace gases	Adjusted to the AICC2012 chronology Veres et al. (2013) 21-0 ka: CO2 = Transient, as per Bereiter et al. (2015): [ Access to data (md5sum = c54a033d8cbf588bc2b95d3b92ff9b1c) ] CH4 = Transient, as per Loulergue et al. (2008): [ Access to data ] N2O = Transient, as per Schilt et al. (2010): [ Access to data ] CFC = 0 O3 = Preindustrial (e.g. 10 DU)
Ice sheet	Transient, with a choice of either : - ICE-6G_C reconstruction: [ Access to data ] - GLAC-1D reconstruction: [ Access to data ] How often to update the ice sheet is optional
Orography and coastlines	Transient. To be consistent with the choice of ice sheet. Orography is updated on the same timestep as the ice sheet. It is optional how often the land-sea mask is updated, but ensure consistency with the ice sheet reconstruction is maintained
Bathymetry	Keep consistent with the coastlines, and otherwise use either: - Data associated with the ice sheet; it is optional how often the bathymetry is updated - Preindustrial bathymetry
River routing	Ensure that rivers reach the coastline It is recommended (optional) to use one of the following: - Preindustrial configuration for the model - Transient routing provided with the ice sheet reconstruction (if available) - Manual/model calculation of river network to match topography
Freshwater fluxes	At participant discretion. Three options are: melt-uniform, melt-routed and no-melt: - Melt-uniform : use a globally uniform ice meltwater flux, e.g. as associated with one of the ice sheet reconstructions [ ICE-6G_C ] - [ GLAC-1D ] - Melt-routed : use a routed ice meltwater flux, e.g. as associated with one of the ice sheet reconstructions [ ICE-6G_C ] - [ GLAC-1D ] - No-melt : have no ice sheet meltwater in the simulation It is recommended (optional) to run at least one Core simulation with a scenario consistent with the chosen ice sheet reconstruction to conserve salinity.
Vegetation & land cover Aerosols (dust)	Prescribed preindustrial cover or dynamic vegetation model Prescribed preindustrial distribution or prognostic aerosols

Focused simulations

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References cited

Bereiter, B., Eggleston, S., Schmitt, J., Nehrbass-Ahles, C., Stocker, T. F., Fischer, H., Kipfstuhl, S. and Chappellaz, J.: Revision of the EPICA Dome C CO2 record from 800 to 600 kyr before present, Geophys. Res. Lett., 42(2), 2014GL061957, doi:10.1002/2014GL061957, 2015.

Berger, A.: Long-Term Variations of Daily Insolation and Quaternary Climatic Changes, J. Atmospheric Sci., 35(12), 2362–2367, doi:10.1175/1520-0469(1978)035<2362:LTVODI>2.0.CO;2, 1978.

Kageyama, M., Braconnot, P., Harrison, S. P., Haywood, A. M., Jungclaus, J., Otto-Bliesner, B. L., Peterschmitt, J.-Y., Abe-Ouchi, A., Albani, S., Bartlein, P. J., Brierley, C., Crucifix, M., Dolan, A., Fernandez-Donado, L., Fischer, H., Hopcroft, P. O., Ivanovic, R. F., Lambert, F., Lunt, D. J., Mahowald, N. M., Peltier, W. R., Phipps, S. J., Roche, D. M., Schmidt, G. A., Tarasov, L., Valdes, P. J., Zhang, Q. and Zhou, T.: PMIP4-CMIP6: the contribution of the Paleoclimate Modelling Intercomparison Project to CMIP6, Geosci. Model Dev. Discuss., 1–46, doi:10.5194/gmd-2016-106, 2016.

Loulergue, L., Schilt, A., Spahni, R., Masson-Delmotte, V., Blunier, T., Lemieux, B., Barnola, J.-M., Raynaud, D., Stocker, T. F. and Chappellaz, J.: Orbital and millennial-scale features of atmospheric CH4 over the past 800,000 years, Nature, 453(7193), 383–386, doi:10.1038/nature06950, 2008.

Schilt, A., Baumgartner, M., Schwander, J., Buiron, D., Capron, E., Chappellaz, J., Loulergue, L., Schüpbach, S., Spahni, R., Fischer, H. and Stocker, T. F.: Atmospheric nitrous oxide during the last 140,000 years, Earth Planet. Sci. Lett., 300(1–2), 33–43, doi:10.1016/j.epsl.2010.09.027, 2010.

Veres, D., Bazin, L., Landais, A., Toyé Mahamadou Kele, H., Lemieux-Dudon, B., Parrenin, F., Martinerie, P., Blayo, E., Blunier, T., Capron, E., Chappellaz, J., Rasmussen, S. O., Severi, M., Svensson, A., Vinther, B. and Wolff, E. W.: The Antarctic ice core chronology (AICC2012): an optimized multi-parameter and multi-site dating approach for the last 120 thousand years, Clim Past, 9(4), 1733–1748, doi:10.5194/cp-9-1733-2013, 2013.