Caple AUF900 Uživatelský manuál stáhnout pdf (Strana 280)

278

ENSI Erfahrungs- und Forschungsbericht 2011

Project goals

Deep geological repositories for radioactive waste

need to be save for up to one million years. For

such a long perspective glacial periods and the

potential influence of deep erosion due to glaciers

have to be considered for the repository sites. The

aim of this project is to investigate the impact of

different glacial boundary conditions on the at-

mospheric dynamics and the precipitation pattern,

and to identify the influence of the changes on the

glaciers in Switzerland.

Work carried out

and results obtained

Experimental setup

The project is based on simulations with a global

atmosphere general circulation model (Communi-

ty Climate System Model version 4, [1]) with pre-

scribed sea surface temperatures (SST) and sea ice

extent. The model is run in a 0.9 ° × 1.25 ° horizon-

tal resolution and the prescribed lower boundary

conditions are taken from simulations with a ful-

ly-coupled but lower resolved atmosphere-ocean

general circulation model.

To investigate the sensitivity of the glacial climate

to changes in the boundary conditions a set of

nine time-slice experiments is conducted consid-

ering four different periods: present-day (1990

AD; 1 simulation), preindustrial (1850 AD; 1 sim-

ulation), Last Glacial Maximum (21 ka ago, LGM;

2 simulations), and Middle Weichselian (65 ka ago,

MW; 5 simulations). In all cases the time-slice ex-

periments represent equilibrium states. The seven

glacial simulations allow to investigate the sensi-

tivity to the SST and sea ice distribution, to the ex-

ternal forcing (orbital and greenhouse gases), and

to the ice sheet distribution.

The influence of the ocean surface forcing is ana-

lyzed using the two LGM simulations (called LGM1

and LGM2) as they differ only in this aspect. To in-

vestigate the impact of the radiative forcing the

LGM simulations are compared to a MW simula-

tion with the same ice sheet topography as in LGM

(MWLGM). Finally, four different ice sheet topog-

raphies are applied in the other MW simulations.

The two simulations of the recent past are used

only as reference states for the changes found in

the glacial simulations (PD = present-day, PI = pre-

industrial).

For the four time periods, the values for the Earth's

orbital parameters are calculated according to [2]

and the concentrations of the greenhouse gases

are estimated from ice core measurements. The

topography and the coastlines for the glacial sim-

ulations are based on the ICE-5G reconstruction

of [3] for LGM, which corresponds to a sea lev-

el change of 120 m. However, for the MW simu-

lations (except MWLGM) the total ice mass is re-

duced – by lowering the height of the ice sheets –

to the equivalent of a 80 m sea level change. The

reduction is applied either evenly (MWLIN), mostly

to the Fennoscandian ice sheet (MWEU), only to

the Laurentide ice sheet (MWUS), or to the Lau-

Figure 1:

LGM ice sheet extent (all

colored areas) and thick-

ness (contours, interval

1 km), and additional land

areas in MW (black) and

LGM (black and gray). The

different colors indicate

the regions of the stron-

gest reduction of the ice

sheet height in the MW

simulations compared

with the LGM one (see also

text): red and orange for

MWEU, green for MWUS,

and green and orange for

MWNS. The coastlines

and ice sheets for LGM

are based on ICE-5G [3].

The shift of the coastlines

(shown as the boundary

of 50 % land fraction)

corresponds to a sea-level

change of 80 m (MW) and

120 m (LGM).

1 2 ... 275 276 277 278 279 280 281 282 283 284 285 ... 303 304

Caple AUF900 Uživatelský manuál Strana 280

Komentáře k této Příručce

Caple AUF900 Uživatelský manuál Strana 280

Komentáře k této Příručce

Související produkty a manuály pro ne Caple AUF900