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--- pmip3:wg:degla:bc:ice [2015/02/18 16:04] – ruza
+++ pmip3:wg:degla:bc:ice [2025/05/15 17:50] (current) – jypeter
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-/* ~~DISCUSSION|Discussion on core experiment design~~ *
+~~DISCUSSION:closed|Discussion on core experiment ice sheets~~
 ====== Last Deglaciation Ice Sheets ======
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 [[pmip3:wg:degla:bc:core|Go back]] to the main core experiment design page. \\
 [[pmip3:wg:degla:index|Go back]] to the main working group page. \\
-Please note, this page is a work in progress and is not ready for discussion yet. \\
 \\
-Please use the //Discussion// section below to specifically comment on the choice of __ice sheet reconstructions__ for the core experiment. \\ \\
+Please use the //Discussion// section below to specifically comment on the choice of __ice sheet reconstructions__ for the core experiment.
+\\ \\
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 For the core experiment, there is a choice of two global ice sheet reconstructions:
-  * [[pmip3:wg:degla:bc:ice#ICE6G_C_Reconstruction | ICE6G_C]], provided by Dick Peltier, Rosmarie Drummond and co-authors
+  * [[pmip3:wg:degla:bc:ice#ICE-6G_C_Reconstruction | ICE-6G_C]], provided by Dick Peltier, Rosmarie Drummond and co-authors
-  * [[pmip3:wg:degla:bc:ice#Lev_Tarasov's_Reconstruction | Lev Tarasov's reconstruction]], provided by Lev Tarasov and co-authors.
+  * [[pmip3:wg:degla:bc:ice#GLAC-1D_Reconstruction | GLAC-1D]], provided by Lev Tarasov and co-authors.
-Please one of these reconstructions for your Last Glacial Maximum (LGM) experiment, as per the LGM working group requirements, and continue to use the same reconstruction through the transient last deglaciation core simulation. \\
+Please use one of these reconstructions for your Last Glacial Maximum (LGM) experiment (e.g. equilibrium type spinup at 21 ka), and continue to use the same reconstruction through the transient last deglaciation Core simulation. \\
 \\
-Those groups that are able may wish to carry out two simulations; one with each ice sheet reconstruction. \\ \\
+Those groups that are able may wish to carry out two simulations; one with each ice sheet reconstruction.  \\
+\\
+This page contains a lot of information; use the 'Table of Contents' (top right) to navigate through! \\ \\
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-====== ICE6G_C Reconstruction ======
+====== ICE-6G_C reconstruction ======
 \\
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   * 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 (2015). \\ \\
-===== Information about the reconstruction =====
+===== The reconstruction =====
 Information provided by Dick Peltier, October 2014:
@@ Line 45: / Line 45: @@
 \\
-==== Ice Evolution, 21-0 ka ====
+==== Ice evolution, 21-0 ka ====
-The ice mask in this reconstruction is fractional. For the purpose of the animations (below), we have used > 80 % ice cover per grid cell. The timestep is 500 years.<sup>[1-2]</sup> ((Animations produced by Ruza Ivanovic, Feb 2015))  \\ {{http://homepages.see.leeds.ac.uk/~earri/pmip_deglac/ICE6G_C_NH_last_deglac.gif?400 |ICE6G_C Northern Hemisphere}}
+The ice mask in this reconstruction is fractional. For the purpose of the animations (below), we have used > 80 % ice cover per grid cell. The timestep is 500 years. Horizontal resolution is 1 degree, but it will also be available at 10 arcminute resolution. <sup>[1-2]</sup> ((Animations produced by Ruza Ivanovic, Feb 2015))  \\ {{http://homepages.see.leeds.ac.uk/~earri/pmip_deglac/ICE-6G_C_NH_last_deglac.gif?400 |ICE-6G_C Northern Hemisphere}}
-{{ http://homepages.see.leeds.ac.uk/~earri/pmip_deglac/ICE6G_C_SH_last_deglac.gif?400 |ICE6G_C Southern Hemisphere}}
+{{ http://homepages.see.leeds.ac.uk/~earri/pmip_deglac/ICE-6G_C_SH_last_deglac.gif?400 |ICE-6G_C Southern Hemisphere }}
  \\
-==== Sea Level Equivalent ====
+==== Sea Level Equivalent (SLE) ====
 The information in this section was provided directly by Dick Peltier et al., October 2014:
+> Time dependent //ice-equivalent// contribution to eustatic sea level rise [relative to present day] from each of the primary geographical regions from which grounded ice loss occurred during the [last] deglaciation process. ((Plot provided by Dick Peltier, October 2014)) {{ http://homepages.see.leeds.ac.uk/~earri/pmip_deglac/ICE-6GC_ESL.png?500 |ICE-6G_C Eustatic Sea Level Equivalent of ice volume }}
-> Time dependent //ice-equivalent// contribution to eustatic sea level rise [relative to present day] from each of the primary geographical regions from which grounded ice loss occurred during the [last] deglaciation process. ((Plot provided by Dick Peltier, October 2014)) {{ http://homepages.see.leeds.ac.uk/~earri/pmip_deglac/ICE6GC_ESL.png?400 |ICE6G_C Eustatic Sea Level Equivalent of ice volume }}
 ^  Ice-equivalent contribution to eustatic sea level rise (m) ((relative to present day and assuming ocean area = 360,768,600 km<sup>2</sup>))  ^^^^
-^ ^ Final ICE-4G ^ ICE-5G v1.2 ^ ICE6G_C ^
+^ ^ Final ICE-4G ^ ICE-5G v1.2 ^ ICE-6G_C ^
 ^ 26 ka | | | |
 | N. America (incl. Inuit area) | 54.92 | 83.71	| 87.01 |
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 | E. Antarctica | 8.35 | 8.36 | 6.21 |
 | **TOTAL** | **114.12** | **123.65** | **113.68** |
- \\
-===== Smoothed fields =====
-Dick Peltier has suggested that ICE6G_C topographies could be provided as smoothed fields:
->...we could...provide these [ICE6G_C] topographies in the form of the smooth fields obtained by projecting them onto the set of spherical harmonics employed in a 1 degree by 1 degree model in the CMIP5 class. The results you obtain when you do this are illustrated in [Peltier and Vettoretti (2014)]<sup>[3]</sup>.  Would you rather have these fields in the smoothed form actually seen by such a climate model? This might be a good idea since some groups may be employing grid point models and these groups would probably appreciate being given a smooth topography field to start with.
 \\
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 Although ice meltwater fluxes should not be prescribed for the Core simulation, groups may wish to run alternative simulations with meltwater fluxes to the oceans. \\
 \\
-At this stage it is proposed that ICE6G_C meltwater routing can be calculated from ice thickness at each timestep. It will not be explicitly provided by the working group.
+At this stage it is proposed that ICE-6G_C meltwater routing can be calculated from ice thickness at each timestep. It will not be explicitly provided by the working group.
 \\
 See the //alternative// [[pmip3:wg:degla:bc:alt | full transient simulations ]]  page for more info. [not live yet]
+ \\
+===== Smoothed fields =====
+Dick Peltier has suggested that ICE-6G_C topographies could be provided as smoothed fields (October 2014):
+>...we could...provide these [ICE-6G_C] topographies in the form of the smooth fields obtained by projecting them onto the set of spherical harmonics employed in a 1 degree by 1 degree model in the CMIP5 class. The results you obtain when you do this are illustrated in [Peltier and Vettoretti (2014)]<sup>[3]</sup>.  Would you rather have these fields in the smoothed form actually seen by such a climate model? This might be a good idea since some groups may be employing grid point models and these groups would probably appreciate being given a smooth topography field to start with.
 \\
 ===== Further notes =====
 Provided by Dick Peltier, October 2014:
 > Paleo-topography data sets contain information on BOTH the topography of the continents with respect to sea level at specific times in the past as well as paleo-bathymetry of the oceans at the same sequence of times. It is not only the former field that is important but also the latter.  Although we could produce a separate data set for an "altitude anomaly" for the continents we would also have to produce a "bathymetric anomaly" for the oceans . The latter is as important as the former because modern climate models , eg the NCAR CESM model, have begun to include a diapycnal diffusivity field that is linked to mixing associated with the dissipation of the internal tide produced by the flow of the barotropic tide over ocean bottom topography. In order to re-tune such mixing parameterizations for past times, it is necessary to produce new models of the barotropic tide and this requires the different bathymetry of the oceans for these past times. It is very important in my opinion that the paleo-bathymetry be made available to the community as well as the paleo-topography. \\
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-====== Lev Tarasov's Reconstruction ======
+====== GLAC-1D reconstruction ======
+AKA //Tarasov// or //Tarasov et al.// reconstruction.
 \\
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-===== Ice Evolution, 21-0 ka =====
+===== The reconstruction =====
-The ice mask in this reconstruction is based on 100 % ice or no ice. The timestep is currently 1000 years, but could be provided at 500 years, if desired. <sup>[4-7]</sup>((Animations produced by Ruza Ivanovic, Feb 2015)) \\
-{{http://homepages.see.leeds.ac.uk/~earri/pmip_deglac/Tarasov_NH_last_deglac.gif?400 |Lev Tarasov's Northern Hemisphere ice}}
+==== Ice Evolution, 21-0 ka ====
-{{ http://homepages.see.leeds.ac.uk/~earri/pmip_deglac/Tarasov_SH_last_deglac.gif?400 |Lev Tarasov's Southern Hemisphere ice}}
+The ice mask in this reconstruction is based on 100 % ice or no ice. The timestep is currently 1000 years, but could be provided at 500 years, if desired. Horizontal resolution is 1 degree. <sup>[4-7]</sup>((Animations produced by Ruza Ivanovic, Feb 2015)) \\
+{{http://homepages.see.leeds.ac.uk/~earri/pmip_deglac/Tarasov_NH_last_deglac.gif?400 |GLAC-1D's Northern Hemisphere ice}}
+{{ http://homepages.see.leeds.ac.uk/~earri/pmip_deglac/Tarasov_SH_last_deglac.gif?400 |GLAC-1D's Southern Hemisphere ice}}
+ \\
+==== Ice volume ====
+Ice volume of the constituent ice sheets through time.<sup>[4-7]</sup> ((Plot produced by Lauren Gregoire, Feb 2015)) \\
+{{ http://homepages.see.leeds.ac.uk/~earri/pmip_deglac/Ice_Sheets_Tarasov.png? |GLAC-1D ice volume through time}}
  \\
+===== Meltwater =====
+Although ice meltwater fluxes should not be prescribed for the Core simulation, groups may wish to run alternative simulations with meltwater fluxes to the oceans. \\
+\\
+A timeseries of global meltwater routing (river mouth discharge) that is consistent with GLAC-1D's ice sheet reconstruction will be provided. \\
+\\
+See the //alternative// [[pmip3:wg:degla:bc:alt | full transient simulations ]]  page for more info. [not live yet]
+\\
 ===== Information about the reconstruction =====
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 \\
-----
-===== Meltwater =====
-Although ice meltwater fluxes should not be prescribed for the Core simulation, groups may wish to run alternative simulations with meltwater fluxes to the oceans. \\
-\\
-A timeseries of global meltwater routing (river mouth discharge) that is consistent with Lev Tarasov's ice sheet reconstruction will be provided. \\
-\\
-See the //alternative// [[pmip3:wg:degla:bc:alt | full transient simulations ]]  page for more info. [not live yet]
-\\
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-====== Points To Discuss ======
+====== 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.]
-  * Should ICE6G_C be provided here in its smoothed format, as offered by Dick Peltier (above;  [[pmip3:wg:degla:bc:ice#smoothed_fields]]), its original unsmoothed format, or both?
+  * No specific points raised yet.\\ \\
-  * Should Lev Tarasov's reconstruction be provided with a 500 year timestep? It is currently 1000 years, but can be rerun with a shorter timestep.\\ \\
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