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====== Last Deglaciation Core Experiment Design ======

<note info>\\ Contacts: [[R.Ivanovic@leeds.ac.uk|Ruža Ivanović]], [[L.J.Gregoire@leeds.ac.uk|Lauren Gregoire]], [[Didier.Roche@lsce.ipsl.fr|Didier Roche]]</note>

[[pmip3:wg:degla:index|Go back]] to the main working group page. \\


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===== Proposal =====
Following wide consultation, this is our experiment design for the last deglaciation core simulation. It is currently in //Geoscientific Model Development Discussions//:\\
[[http://www.geosci-model-dev-discuss.net/8/9045/2015/gmdd-8-9045-2015.html | Ivanovic, R. F., L. J. Gregoire, M. Kageyama, D. M. Roche, P. J. Valdes, A. Burke, R. Drummond, W. R. Peltier, and L. Tarasov (2015), Transient climate simulations of the deglaciation 21–9 thousand years before present; PMIP4 Core experiment design and boundary conditions, Geosci Model Dev Discuss, 8(10), 9045–9102, doi:10.5194/gmdd-8-9045-2015]]\\
\\
To make sure we incorporate your comments in the final, published experiment design, please use GMD's [[http://www.geosci-model-dev-discuss.net/8/9045/2015/gmdd-8-9045-2015-discussion.html | discussion]] facility for the manuscript, which will stay open until 16th December 2015.\\

The published version of the experiment design is/will be the definitive version and supersedes any differences on this wiki. Data will be available to download from this wiki when the manuscript is accepted in its final state.

Please use the //Discussion// section below and our mailing list for __general__ discussion on the working group.
 \\ 
There are also the following dedicated pages:
  * [[pmip3:wg:degla:bc:orb | orbital parameters]] page
  * [[pmip3:wg:degla:bc:ghg | greenhouse gases]] page
  * [[pmip3:wg:degla:bc:ice | ice sheets]] page
  * [[pmip3:wg:degla:bc:melt | ice meltwater fluxes]] [to the ocean] page \\ \\



==== Transient simulation 21-9 ka ====

All core simulations must span this time-period. Note that forcings provided will run 21-0 ka. \\
Please use:

  * An **equilibrium-type LGM** climate simulation to initialise the transient simulation, OR a **transient 26-21 ka LGM ** simulation. See below.
  * **[[pmip3:wg:degla:bc:orb | Orbital parameters]]** as per [[http://journals.ametsoc.org/doi/abs/10.1175/1520-0469%281978%29035%3C2362%3ALTVODI%3E2.0.CO%3B2 | Berger (1978)]]<sup>[1]</sup>.
  * **[[pmip3:wg:degla:bc:ghg | Greenhouse gases]]**:
      * **CO<sub>2</sub>** from EPICA Dome C [[http://www.nature.com/nature/journal/v453/n7193/full/nature06949.html | (Lüthi et al., 2008)]]<sup>[2]</sup> on the AICC2012 timescale [[http://www.clim-past.net/9/1733/2013/cp-9-1733-2013.html | (Veres et al., 2013)]]<sup>[3]</sup>. ((The high resolution [[http://www.nature.com/nature/journal/v514/n7524/full/nature13799.html | Marcott et al. (2014)]]<sup>[4]</sup> record could be used for an alternative simulation to the core, but not for the core.))
      * **CH<sub>4</sub>** from EPICA Dome C [[http://www.nature.com/nature/journal/v453/n7193/full/nature06950.html | (Loulergue et al., 2008)]]<sup>[5]</sup> on the AICC2012 timescale [[http://www.clim-past.net/9/1733/2013/cp-9-1733-2013.html | (Veres et al., 2013)]]<sup>[3]</sup>.
      * **N<sub>2</sub>O** from TALDICE [[http://www.sciencedirect.com/science/article/pii/S0012821X10006023 | (Schilt et al., 2010)]]<sup>[6]</sup> on the AICC2012 timescale [[http://www.clim-past.net/9/1733/2013/cp-9-1733-2013.html | (Veres et al., 2013)]]<sup>[3]</sup>.
  * **[[pmip3:wg:degla:bc:ice | Ice sheets]]**: Choice of either the [[pmip3:wg:degla:bc:ice#ice-6g_c_reconstruction | ICE-6G_C]]<sup>[7-8]</sup> or [[pmip3:wg:degla:bc:ice#glac-1d | GLAC-1D]]<sup>[9-12]</sup> global reconstruction of ice sheet evolution. \\ Whichever is chosen for the LGM should be kept for the whole simulation. \\ [See the [[pmip3:wg:degla:bc:ice | last deglaciation ice sheets]] page for more information on the ice sheets.]
  * **[[pmip3:wg:degla:bc:melt | Ice meltwater fluxes]]**: __no meltwater__ in the core. ((Global meltwater fluxes that are consistent with the ice sheet reconstructions will be provided for alternative simulations to the core, but must not be used for the core.)) 
  * Other boundary conditions: keep as per the LGM. For example :
      * Vegetation can be fixed (to pre-industrial) or interactive
      * Dust can be fixed (to pre-industrial) or prognostic \\ \\

==== Equilibrium-type LGM 21 ka ====

In some cases, the following constraints may differ from other PMIP 21 ka experiments. If possible, please make sure you use the setup described here:
  * Orbital parameters:
    * eccentricity: 0.018994
    * obliquity: 22.949°
    * perihelion–180°: 114.42°
    * vernal equinox: 21st March at noon
  * Solar constant: same as for the preindustrial (e.g. 1365 W/m2)
  * Trace gases:
    * CO2: 188 ppm
    * CH4: 375 ppb
    * N2O: 200 ppb
    * CFCs: 0 
    * O3: same as PMIP3/CMIP5 preindustrial (e.g. 10 DU)
  * Ice sheets: [[pmip3:wg:degla:bc:ice#ice-6g_c_reconstruction | ICE-6G_C]] or [[pmip3:wg:degla:bc:ice#glac-1d | GLAC-1D]] - use whichever you will use for the ensuing transient simulation
  * Topography and coastlines: as per the chosen ice sheet. Please ensure that rivers reach the ocean.
  * Bathymetry: Optional. If possible, as per the chosen ice sheet. Otherwise, up to the user to decide.
  * Global ocean salinity: +1 psu
  * Freshwater budget: Please note the PMIP LGM advice to try to avoid unnecessary ocean salinity drifts. You may need to route excess snow to the ocean.
  * Other boundary conditions: consistent with the Core\\ \\

==== 26-21 ka LGM ====

For those who wish to begin their simulation from before the PMIP LGM, use the following transient data:
  * Orbit as per [[http://journals.ametsoc.org/doi/abs/10.1175/1520-0469%281978%29035%3C2362%3ALTVODI%3E2.0.CO%3B2 | Berger (1978)]]<sup>[1]</sup> for this time period.
  * Greenhouse gases as per [[http://www.nature.com/nature/journal/v453/n7193/full/nature06949.html | Lüthi et al. (2008)]]<sup>[2]</sup>, [[http://www.nature.com/nature/journal/v453/n7193/full/nature06950.html | Loulergue et al. (2008)]]<sup>[5]</sup> and [[http://www.sciencedirect.com/science/article/pii/S0012821X10006023 | Schilt et al. (2010)]]<sup>[6]</sup>, respectively, on the AICC2012 chronology [[http://www.clim-past.net/9/1733/2013/cp-9-1733-2013.html | (Veres et al., 2013)]]<sup>[3]</sup>. 
  * All other boundary conditions as per the //Equilibrium-type LGM 21 ka//.\\ \\

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===== Points to discuss =====

Please think about the following points and add any comments on these or any other aspects of the experiment design to the discussion section below: [Topics will be added here as they are raised below or by email.]
  * No specific points yet. \\ \\

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===== References =====
  - Berger, A. Long-Term Variations of Daily Insolation and Quaternary Climatic Changes. J. Atmospheric Sci. 35(12), 2362–2367 (1978).
  - Lüthi, D. et al. High-resolution carbon dioxide concentration record 650,000–800,000 years before present. Nature 453, 379–382 (2008).
  - Veres, D. et al. The Antarctic ice core chronology (AICC2012): an optimized multi-parameter and multi-site dating approach for the last 120 thousand years. Clim Past 9, 1733–1748 (2013).
  - Marcott, S. A. et al. Centennial-scale changes in the global carbon cycle during the last deglaciation. Nature 514, 616–619 (2014).
  - Loulergue, L. et al. Orbital and millennial-scale features of atmospheric CH4 over the past 800,000 years. Nature 453, 383–386 (2008).
  - Schilt, A. et al. Atmospheric nitrous oxide during the last 140,000 years. Earth Planet. Sci. Lett. 300, 33–43 (2010).
  - Argus, D. F., Peltier, W. R., Drummond, R. & Moore, A. W. The Antarctica component of postglacial rebound model ICE-6G_C (VM5a) based on GPS positioning, exposure age dating of ice thicknesses, and relative sea level histories. Geophys. J. Int. ggu140 (2014).
  - Peltier, W. R., Argus, D. F. & Drummond, R. Space geodesy constrains ice age terminal deglaciation: The global ICE-6G_C (VM5a) model. J. Geophys. Res. Solid Earth 2014JB011176 (2015).
  -  Tarasov, L. & Peltier, W. R. Greenland glacial history and local geodynamic consequences. Geophys. J. Int. 150, 198–229 (2002).
  - Tarasov, L., Dyke, A. S., Neal, R. M. & Peltier, W. R. A data-calibrated distribution of deglacial chronologies for the North American ice complex from glaciological modeling. Earth Planet. Sci. Lett. 315–316, 30–40 (2012)
  - Briggs, R. D., Pollard, D. & Tarasov, L. A data-constrained large ensemble analysis of Antarctic evolution since the Eemian. Quat. Sci. Rev. 103, 91–115 (2014).
  - Tarasov et al. Eurasian ice sheet evolution (in prep.).\\ \\

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