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--- pmip3:design:21k:icesheet:index [2009/09/09 08:19]
pasb
+++ pmip3:design:21k:icesheet:index [2009/09/23 12:50]
jypeter Major update of the "Ice volume" section
@@ Line 2: / Line 2: @@
 ====== Ice Sheet for PMIP3/CMIP5 simulations  ======
-This page synthesises the Ongoing work for the definition of a new ice-sheet reconstruction to be used in LGM simulations for PMIP3/CMIP5.
+<note warning>This page synthesises the **ongoing work** for the definition of a new ice-sheet reconstruction to be used in LGM simulations for PMIP3/CMIP5.\\ \\ Use the [[index#page_bottom_tag|discussion]] panel at the end of the page for comments </note>
 ===== Introduction =====
@@ Line 24: / Line 27: @@
 ==== Lev-MOCA  ====
-=== Northern Hemispheric components (GLAC-1) ===
+=== Northern Hemisphere (GLAC-1) ===
 The Greenland reconstruction is the GrB model described in Tarasov and Peltier( GJI 2002 and JGR 2003).  It's a hand tuning of a 3D thermo-mechanically coupled glaciological shallow ice-sheet model and visco-elastic bedrock response model (using the same VM2 rheology used for ICE-5G) to fit the Relative Sea-Level (RSL) observations, the GRIP borehole temperature and age profiles, and approximate basal temperatures at CampCentury and Dye3 along with secondary constraints described in the references.
-The North American and Eurasian reconstructions are objective Bayesian calibrations of the MUN/UofT glacial systems model (above 3D model plus asynchronously coupled down-slope surface drainage/lake depth solver, and various other components such as a thermodynamic lake ice, sub-glacial till-deformation, ice-shelf represention,..., some of which are described in Tarasov and Peltier, QSR 2004, and Nature 2005, and a more complete description is currently being written up). The calibration involves approximately 30 ensemble parameters to capture uncertainties in deglacial uncertainties in deglacial climate and ice dynamics. Model runs cover a full glacial cycle. The climate forcing for the calibration is based on interpolation between a glacial state (based on a combination of PMIPI for North America and PMIP II for Eurasia) LGM model output temperature and precipitation climatologies along with further regional precipitation controls) and a present-day climatology. The interpolation between glacial and present-day states is weighted to the regional temperature chronology from the tuned Greenland reconstruction.  Calibration targets include a large set of RSL observations, geologically-inferred deglacial ice-margin chronologies, and geodetic constraints. For the case of North America, the calibrated ensemble is further scored with respect to strand-lines (paleo lake level indicators) and Marine Limit (maximum level of marine inundation) observations.
+The North American and Eurasian reconstructions are objective Bayesian calibrations of the MUN/UofT glacial systems model (above 3D model plus asynchronously coupled down-slope surface drainage/lake depth solver, and various other components such as a thermodynamic lake ice, sub-glacial till-deformation, ice-shelf represention,..., some of which are described in Tarasov and Peltier, QSR 2004, and Nature 2005, and a more complete description is currently being written up). The calibration involves approximately 30 ensemble parameters to capture uncertainties in deglacial climate and ice dynamics. Model runs cover a full glacial cycle. The climate forcing for the calibration is based on interpolation between a LGM (based on a combination of PMIPI for North America and PMIP II for Eurasia) model output temperature and precipitation climatologies (along with further regional precipitation controls) and a present-day climatology. The interpolation between glacial and present-day states is weighted to the regional temperature chronology from the tuned Greenland reconstruction.  Calibration targets include a large set of RSL observations, geologically-inferred deglacial ice-margin chronologies, and geodetic constraints. For the case of North America, the calibrated ensemble is further scored with respect to strand-lines (paleo lake level indicators) and Marine Limit (maximum level of marine inundation) observations.
 The data sets for North America and Eurasia will include surface elevation, ice mask, lake depth, surface drainage routing pointer fields and ice flux components of the surface drainage.
@@ Line 35: / Line 38: @@
 === Southern hemisphere ===
-Glaciological constraints have shown that the ice5G reconstruction was too high in East Antarctica. Several tests are now made using a revised version of ICE-5G (VM2=ICE-6G) to correct this aspect while keeping the global on see level and other geomorphological constraints. Dick Peltier’s group is working now on smoothing the refine model and taking the extension of the loading of the shelf out to a distance from the present coast consistent with a specific bathymetry contour. The final version should be ready by September.
+Glaciological constraints have shown that the ICE-5G reconstruction was too high in East Antarctica. Several tests are now made using a revised version of ICE-5G (VM2=ICE-6G) to correct this aspect while keeping the global on sea level and other geomorphological constraints. Dick Peltier’s group is working now on smoothing the refined model and taking the extension of the loading of the shelf out to a distance from the present coast consistent with a specific bathymetry contour. The final version should be ready by September.
@@ Line 46: / Line 49: @@
 They are provided for evaluation and test, and do not correspond to the "official" boundary condition to be used for LGM simulations in CMIP5.
-Here are also two submitted papers where you can find information about the new ice-sheet that are provided by Dick.
+=== References ===
+Note: get in touch with [[pmip2web@lsce.ipsl.fr|Jean-Yves Peterschmitt]] in you need a copy of the following papers.
+  * Peltier, W.R., 2009, //Closure of the budget of global sea level rise over the GRACE Era: The importance and magnitudes of the required corrections for global glacial isostatic adjustment//. Quat. Sci. Rev. 28, 1658-1674.
+  * Donald F. Argus and W. R. Peltier, 2009. //Constraining models of postglacial rebound using space geodesy: A detailed assessment of model ICE-5G (VM2) and its relatives//, Geophysical Journal International, submitted.
+  * W.R. Peltier and R. Drummond, 2008. //Rheological stratification of the lithosphere: A direct inference basd upon the geodetically observed pattern of the glacial isostatic adjustment of the North American continent//. geophys. res. Lett., vol. 35, L16314, doi:10.1029/2008GL034586.
+=== Data ===
+<note tip>You should download the {{:pmip3:design:21k:icesheet:ice-ng_compare_polar.pdf}} file if you want to look at detailed graphics comparing the different versions of ICE-nG (56 Mb, 77 pages)</note>
 Notes:
+  * Get in touch with [[pmip2web@lsce.ipsl.fr|Jean-Yves Peterschmitt]] if you want to download the netcdf files used to generate the figures below
   * Click on a figure to get the full size version
-  * You can compare the figures with the [[http://pmip2.lsce.ipsl.fr/design/ice5g /ice5g_v1_1.shtml|ICE-5G v1.1 (PMIP2)]] and [[http://pmip2.lsce.ipsl.fr/design/ice5g/index.shtml|ICE-5G v1.2]] versions avalaible on the PMIP2 web site
+  * You can compare the figures with the ICE-5G versions available on the PMIP2 web site
+    *[[http://pmip2.lsce.ipsl.fr/design/ice5g/ice5g_v1_1.shtml|ICE-5G v1.1 (PMIP2)]]
+    * [[http://pmip2.lsce.ipsl.fr/design/ice5g/index.shtml|ICE-5G v1.2]]
 {{:pmip3:design:21k:icesheet:ice6g_v1.0_00.0k_1deg.png?200| 0 K}}
@@ Line 57: / Line 77: @@
 {{:pmip3:design:21k:icesheet:ice6g_v1.0_21.0k_1deg.png?200|21 K}}
 {{:pmip3:design:21k:icesheet:ice6g_v1.0_26.0k_1deg.png?200|26 K}}
+=== Ice volume ===
+The following table has been supplied by
+[[rmarie@atmosp.physics.utoronto.ca|Rosemarie Drummond]]. It compares
+the ice amounts in the various regions in terms of eustatic sea level
+impact inferred by assuming the ocean area to remain fixed to the
+modern area (//ice amount relative to now in m of ocean assuming ocean
+area = 360768576 km<sup>2</sup>//).
+^ ^  ICE-4G\\ //final//  ^^  ICE-5G\\ //v1.2//  ^^  ICE-6G\\ //v1.0//  ^^
+^ ^  21k  ^  26k  ^  21k  ^  26k  ^  21k  ^  26k  ^
+^ North America\\ (incl Innuit area) |  64.24 |  54.92 |  81.47 |  83.71 |  79.82 |  88.14 |
+^ Greenland & Iceland |  6.38 |  5.43 |  2.49 |  2.45 |  2.36 |  2.34 |
+^ Fennoscandia |  10.39 |  8.91 |  11.19 |  11.79 |  10.22 |  12.31 |
+^ Barents / Kara Seas |  14.05 |  12.26 |  8.43 |  9.29 |  7.26 |  9.10 |
+^ UK |  0.42 |  0.35 |  1.48 |  1.65 |  0.58 |  0.82 |
+^ Patagonia |  0.55 |  0.47 |  0.55 |  0.55 |  0.83 |  0.87 |
+^ West Antarctica |  9.74 |  8.33 |  9.68 |  9.68 |  11.79 |  11.79 |
+^ East Antarctica |  8.35 |  7.12 |  8.36 |  8.36 |  1.45 |  1.44 |
+^ ice-shelves (1) |   |   |   |   |  2.80 |  3.00 |
+^ Total |  **114.12** |  **97.79** |  **123.63** |  **127.48** |  **117.11** |  **129.81** |
+  * (1) The calculation only cares about grounded ice, so where it detects that the ice-model has ice that is below the predicted sea-level, it deems the ice to be melted and added to the ocean. The ice may be melted or be part of an ice-shelf eg the Ronne, Ross ice-shelves. This is a feature of the most recent version of the solver.
+  * The large change between ICE-4G (VM2) and ICE-5G (VM2) is due to the introduction of Art Dyke's margin chronology which had the ice being eliminated from North America earlier than in the original chronology obtained from John Andrews. This meant that more ice had to be removed in order to have the same impact on RSL during the ice-free Holocene interval.
+  * The large differences between ICE-5G (VM2) and ICE-6G (VM5a) are a combined result of the introduction of two further constraints:
+    * the analysis from Valerie Masson demonstrating that the elevation of East Antarctic ice was not significantly different than modern
+    * the results of the analyses based upon the application of the space geodetic constraints described in the Argus and Peltier paper.
+  * The version of the ICE-4G (VM2) model for which data are provided is not exactly the version that was employed in the original PMIP project but rather one from which a significant amount of Antarctic ice was simply eliminated (version employed for illustrative purposes in Peltier's paper for the Mt Hood volume of QSR).
 ====== Conclusion ======
-In September we should be able to compare the results of the revised version of ICE-45G with those of the Lev-Dick collaboration and take a decision based on comparisons with data and on the advice of several specialists
+In September we should be able to compare the results of the revised version of ICE-6G with those of the Lev-Dick collaboration and take a decision based on comparisons with data and on the advice of the community
  ~~DISCUSSION~~
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