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21ka Experimental Design

Page in progress: this is not the final version!

Use the discussion panel add the end of the page for comments

Boundary conditions

Summary of 21ka boundary conditions

PMIP3 Alternative solution
Orbital parameters [ ecc = 0.018994 ] - [ obl = 22.949° ] - [ peri-180° = 114.42° ]
Date of vernal equinox March 21 at Noon
Trace gases [ CO2 = 185 ppm ] - [ CH4 = 350 ppb ] - [ N2O = 200 ppb ] - [ CFC = 0 ] - [ O3 = same as PI ]
Aerosols Same as PI
Solar constant 1365W/m2 As in PI
Vegetation Interactive See specific note below
Ice sheet Revised ICE5G???? (provided)
Topography and coastlines From ???? (provided) minimum changes (see note below)
River outflow Modified according to a river pathway map (provided) Same as PI
Ice sheet melting add excess LGM freshwater (see below) Same as PI
Mean ocean salinity ??? -1PSU everywhere ???

Please use the discussion panel to comment this table!

Vegetation

Depending on the complexity of the model used the vegetation will be either
- computed by the model
- prescribed to PI (some ESM may only compute vegetation phenology and carbon cycle)
- prescribed to 21ka vegetation reconstructed from a combination of model output and data analyses (please use the map provided here)
- Obtained from asynchronous coupling with a DVGM (Biome 4 model provided)

For Earth System Models with interactive carbon cycle

The simlations are forced by CO2 concentrations. Please use the same protocal as in CMIP5 to store the carbone fluxes and the variables needed for PCMIP (see list here)

Insolation

Note that insolation should follows PMIP requirements. Please check it carefuly using the following tables (LGM insolation tables)

River outflow

The river pathways and basins should be at least adjusted so that fresh water is conserved at the Earth's surface: care should be taken that rivers reach the ocean (due to the lower sea level at LGM, some river mouths have to be displaced towards the coast).

Ice-sheet mass balance

It is advised to ensure a closed fresh water balance at the Earth's surface: snow accumulating on the ice-sheets should be redistributed to the oceans, either globally or in the adjacent oceans.

Initial conditions





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Discussion

Lev Tarasov, 2009/02/18 14:27

Ice-sheet mass-balance redistribution is non-trivial. Even if the ice-sheet is assumed to have 0 net mass-balance change, regional discharge will vary. Ie part of the ice-sheet can be growing, another part shrinking resulting in spatially heterogenous discharge to the oceans. Combined drainage/ice-sheet/isostasy modelling can resolve this and create a self-consistent routing map.

A related issue is iceberg versus meltwater discharge. Glaciological models approximately resolve this (we lack well constrained calving models, so emphasis on the “approximate”). Is it worth considering different treatment of freshwater versus ice-berg discharge wrt when mixing can occur in the ocean?

Topography and coastlines need to be a part of the self-consistent ice-sheet/topography package.

PMIP3 Guest Login, ottobli@ucar.edu, 2009/02/21 19:08

A vegetation map for 21ka reconstructed from a combination of model output and data analyses would be very useful for modeling groups that will not be using interactive vegetation in their PI and 20th century runs. We could query groups on the best format. For CCSM, a pft vegetation map would be best.

PMIP3 Guest Login, avkislov@mail.ru and vasilch@geol.msu.ru , 2009/04/03 12:18

We would like to add in this Table (21 ka boundary conditions) the new line “PERMAFROST DISTRIBUTION”. Apart from, we can discuss the scale of Arctic ocean regression during the 21 ka BP as at that time in Yamal, Gydan and Timyr Peninsulas marine terraces were formed. It means that ocean level was high as today. We have the detailed maps of stable isotope distribution in permafrost at this time so we have good instrument for winter temperature reconstruction.

Professors Alexander Kislov and Yurij Vasil’chuk (Moscow State University)

PMIP3 Guest Login, 2009/04/09 10:33

As example, we present two maps, containing the mean January temperature reconstructed based on the signal of the δ18O in ice wedges Professors Alexander Kislov and Yurij Vasil’chuk (Moscow State University)

(unfortunately, maps, probably, can not be represented!)

Fig.1. Sibiria winter palaeotemperatures, reconstructed by δ18O in ice wedges formed 30-25 (a) and 22-14 (b) ka BP.

Jean-Yves Peterschmitt, 2009/04/13 11:13, 2009/05/28 16:29

The figure is now available slightly above in the page

pmip3/design/21k/index.1234449444.txt.gz · Last modified: 2009/02/12 14:37 by jypeter