====== Design for the Last Deglaciation experiment ======

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You will find on this page information about the experiment design for the PMIP4 [[exp_design:degla|Last Deglaciation]] experiments.

Please make sure to read the [[#Associated_publications|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@lsce.ipsl.fr|Jean-Yves Peterschmitt]] | Technical questions or missing data|
| [[R.Ivanovic@leeds.ac.uk|Ruza Ivanovic]] | working group leader |
| [[L.J.Gregoire@leeds.ac.uk|Lauren Gregoire]] | working group co-leader |
| [[Masa.Kageyama@lsce.ipsl.fr|Masa Kageyama]] | working group steering |
| [[Didier.Roche@lsce.ipsl.fr|Didier Roche]] | working group steering |
| [[P.J.Valdes@bristol.ac.uk|Paul Valdes]] | working group steering |
| [[ab276@st-andrews.ac.uk|Andrea Burke]] | working group steering |
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==== Associated publications ====

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

===== Version 1 Specifications =====

For general advice on boundary condition implementation in palaeoclimate models, see [[#References_cited|Kageyama et al. (2018)]].

==== 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 | <wrap em>LDv1-LGMspin</wrap> |
| 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<sup>-2</sup>  | 
| Trace gases  | **CO<sub>2</sub>** = 190 ppm \\ **CH<sub>4</sub>** = 375 ppb \\ **N<sub>2</sub>O** = 200 ppb \\ **CFC** = 0 \\ **O<sub>3</sub>** = Preindustrial (e.g. 10 DU)  | 
| Ice sheets, orography \\ and coastlines  | 21 ka data from either \\ - ICE-6G_C reconstruction: [ [[:data:ice|Access to data]] ] \\ - GLAC-1D reconstruction: [ [[:data:ice|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 | <wrap em>LDv1-transpin</wrap> |
| Astronomical parameters  | All orbital parameters should be transient as per [[#References_cited|Berger (1978)]] 26-21 ka\\ [ [[ftp://ftp.ncdc.noaa.gov/pub/data/paleo/climate_forcing/orbital_variations/insolation/bein1.dat|Access to data]] **&** [[ftp://ftp.ncdc.noaa.gov/pub/data/paleo/climate_forcing/orbital_variations/insolation/readme_insolation.txt|README !]] ]|  
| Trace gases  | All adjusted to the AICC2012 chronology [[#References_cited|Veres et al. (2013)]] 26-21 ka: \\ **CO<sub>2</sub>** = Transient, as per [[#References_cited|Bereiter et al. (2015)]]: [ [[ftp://ftp.ncdc.noaa.gov/pub/data/paleo/icecore/antarctica/antarctica2015co2composite.txt|Access to data]] (md5sum = ''c54a033d8cbf588bc2b95d3b92ff9b1c'') ] \\ **CH<sub>4</sub>** = Transient, as per [[#References_cited|Loulergue et al. (2008)]]: [ [[data:gases#loulergue_et_al_ch4_data|Access to data]] ] \\ **N<sub>2</sub>O** = Transient, as per [[#References_cited|Schilt et al. (2010)]]: [ [[data:gases#schilt_et_al_n20_data|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 | <wrap em>LDv1</wrap> |
| 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 [[#References_cited|Berger (1978)]]\\ [ [[ftp://ftp.ncdc.noaa.gov/pub/data/paleo/climate_forcing/orbital_variations/insolation/bein1.dat|Access to data]] **&** [[ftp://ftp.ncdc.noaa.gov/pub/data/paleo/climate_forcing/orbital_variations/insolation/readme_insolation.txt|README !]] ]|  
| Solar constant | 1361.0 ± 0.51365 W m<sup>-2</sup>  | 
| Trace gases  | Adjusted to the AICC2012 chronology [[#References_cited|Veres et al. (2013)]] 21-0 ka: \\ **CO<sub>2</sub>** = Transient, as per [[#References_cited|Bereiter et al. (2015)]]: [ [[ftp://ftp.ncdc.noaa.gov/pub/data/paleo/icecore/antarctica/antarctica2015co2composite.txt|Access to data]] (md5sum = ''c54a033d8cbf588bc2b95d3b92ff9b1c'') ] \\ **CH<sub>4</sub>** = Transient, as per [[#References_cited|Loulergue et al. (2008)]]: [ [[data:gases#loulergue_et_al_ch4_data|Access to data]] ] \\ **N<sub>2</sub>O** = Transient, as per [[#References_cited|Schilt et al. (2010)]]: [ [[data:gases#schilt_et_al_n20_data|Access to data]] ]\\ **CFC** = 0 \\ **O<sub>3</sub>** = Preindustrial (e.g. 10 DU)  | 
| Ice sheet | Transient, with a choice of either : \\ - ICE-6G_C reconstruction: [ [[:data:ice|Access to data]] ] \\ - GLAC-1D reconstruction: [ [[:data:ice|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\\ [ [[data:ice_ice6g_c#freshwater_fluxes|ICE-6G_C]] ] - [ [[data:ice_glac_1d#freshwater_fluxes|GLAC-1D]] ] \\ - //Melt-routed// : use a routed ice meltwater flux, e.g. as associated with one of the ice sheet reconstructions\\ [ [[data:ice_ice6g_c#freshwater_fluxes|ICE-6G_C]] ] - [ [[data:ice_glac_1d#freshwater_fluxes|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, [[http://onlinelibrary.wiley.com/doi/10.1002/2014GL061957/abstract|doi:10.1002/2014GL061957]], 2015.
  * Berger, A.: **Long-Term Variations of Daily Insolation and Quaternary Climatic Changes**, J. Atmospheric Sci., 35(12), 2362–2367, [[http://journals.ametsoc.org/doi/abs/10.1175/1520-0469(1978)035%3C2362:LTVODI%3E2.0.CO%3B2|doi:10.1175/1520-0469(1978)035<2362:LTVODI>2.0.CO;2]], 1978.
  * **The PMIP4 contribution to CMIP6 – Part 1: Overview and over-arching analysis plan**, Kageyama, M., Braconnot, P., Harrison, S. P., Haywood, A. M., Jungclaus, J. H., 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., Geosci. Model Dev., 11, 1033-1057, [[https://doi.org/10.5194/gmd-11-1033-2018|doi:10.5194/gmd-11-1033-2018]], 2018.
  * 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, [[http://www.nature.com/nature/journal/v453/n7193/full/nature06950.html|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, [[http://www.sciencedirect.com/science/article/pii/S0012821X10006023|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, [[http://www.clim-past.net/9/1733/2013/|doi:10.5194/cp-9-1733-2013]], 2013.