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--- pmip3:design:21k:icesheet:index [2009/10/29 17:22] – Added link to the comparison section jypeter
+++ pmip3:design:21k:icesheet:index [2009/10/29 18:27] – Added references for ANU jypeter
@@ Line 213: / Line 213: @@
     * the results of the analyses based upon the application of the space geodetic constraints described in the Argus and Peltier paper.
+==== ANU Ice Model ====
+<note warning>Please check the [[index#comparing_the_different_reconstructions|Comparison]] section above for the latest plots</note>
+The ANU Ice Model description and data have been supplied by [[Kurt.Lambeck@anu.edu.au|Kurt Lambeck]]
+=== Model description ===
+The ANU ice sheets are based on the inversion of geological sea level and shoreline data supplemented by observational evidence of ice margin locations and, in a few instances, by limiting ice thickness estimates.   These models have evolved over a period of years in an iterative fashion.
+Broadly, the first iterations are based on the analyses of far-field data where the sea-level signal is predominantly a measure of the changes in total ice volume (the ice-volume equivalent sea level or esl) with the principal isostatic component often being the water-load term and a function of the rate at which water is added into or removed from the oceans.  Simple models are initially used for the ice sheets.  The separation of mantle rheology from the esl function is achieved by using the spatial variability of the far-field sea-level signals (Nakada and Lambeck, 1990 #127 see http://rses.anu.edu.au/people/lambeck_k/index.php?p=pubs for references).  The resulting ice function is then redistributed between the ice sheets by using simple scaling relations in the first place and the process is iterated to ensure some convergence (Lambeck, Yokoyama and Purcell, 2002 # 228).
+In parallel inversions are attempted for the individual ice sheets using data from within and close to the ice margins.  These observations are most sensitive to the ice models and mantle rheology.  For the northern hemisphere these analyses are carried out separately for Scandinavia (Lambeck, Smither, and Johnston, 1998 #187, Lambeck et al., in press), Barents-Kara (Lambeck, 1995, 1996 #166, 170), Greenland (Fleming and Lambeck, 2004 #238), British Isles (Lambeck, 1993; 1995 #164, 156) and North America (as yet unpublished).  In all cases new compilations of the field data have been made.  These separate solutions allow for lateral variability in mantle viscosity.  Some interactions between the ice sheets occur and the solutions are therefore iterated.
+The Antarctic field data is insufficient for a similar analysis for the southern hemisphere and we use the difference between the global esl and the northern hemisphere esl to estimate the volume changes for Antarctica eslant (allowing for mountain deglaciation in both hemispheres, Lambeck and Purcell, 2005 #247).  The ice in Antarctica is then distributed according to the LGM ice margins proposed by Anderson et al. (2002) and on the assumption that the ice profiles followed the quasi-parabolic function proposed by Paterson.  The retreat history is determined by the eslant function.  These models are not meant to be accurate reflections of the Antarctic ice history but as a convenient way of disposing of the ice volume that cannot be attributed to the northern hemisphere, in a way that will not impact in a major way on the far-field and northern hemisphere analyses.
+With the new ice models the far-field analysis is repeated and the individual ice sheet analyses are also repeated.  Several such iterations have now been carried out but the successive results have not yet been published.  The LGM results provided here represent the most recent (2009) solution.  The full solutions for some of the ice sheets extend back to MIS-6 (Lambeck et al., 2006 # 252).
+The rebound inversions result in the changes in ice thickness compared to the present day ice volumes.  Thus the LGM ice thickness is obtained by adding the present-day ice thickness.  The LGM ice elevation, with respect to sea level at the LGM is obtained by subtracting the sea-level change (geoid change beneath the ice sheet) from the palaeo ice thickness.
+The esl function as used in the ANU solutions is defined as all land ice and grounded ice on the shelves and the ocean margin at the LGM is defined by the ice grounding line (Lambeck et al., 2003 #233).
+=== References ===
+  * Lambeck & Johnston, 1998: The viscosity of the mantle: evidence from analyses of glacial rebound phenomena. "The Earth's Mantle" (ed. I. Jackson). Cambridge University Press, Cambridge. pp 461-502
+  * Lambeck, Purcell, Johnston, Nakada & Yokoyama, 2003: Water-load definition in the glacio-hydro-isostatic sea-level equation. Quaternary Science Reviews, vol. 22, pp 309-318
+  * Lambeck, & Chappell, 2001: Sea level change through the last glacial cycle. Science, 292, 679-686.
+  * Lambeck, Yokoyama & Purcell, 2002: Into and out of the Last Glacial Maximum: sea-level change during Oxygen Isotope Stages 3 & 2. Quaternary Science Reviews, vol. 21, pp 343-360
+=== Ice volume ===
+The following table has been supplied by [[abeouchi@ccsr.u-tokyo.ac.jp|Ayako Abe-Ouchi]]. 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>//).
+^ ^  ANU  ^  ICE-6G\\ //v1.0//  ^
+^ ^  21k  ^  21k  ^
+^ ANT (1) |  29.0  |  13.2  |
+^ NA (2) |  82.5  |  79.8  |
+^ EUR (3) |  18.2  |  18.1  |
+^ Tot (4) |  129.7  |  111.1  |
+  * (1) //ANT// = East plus West Antarctica
+  * (2) //NA// = Laurentide ice sheet
+  * (3) //EUR// = rest of the ice sheets except for Greenland and Patagonia
+  * (4) //Total// is //excluding Greenland and Patagonia change//
 ====== Conclusion ======