Erfahrungs- und Forschungsbericht 2012 - Ensi

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Erfahrungs- und Forschungsbericht 2012 - Ensi

which are presented in the next sections. More

information and figures dealing with the PI and

the glacial maximum mean states are provided in

the appendix.

Additional simulation with a more elevated

Laurentide ice sheet

There is the possibility that future ice ages might

allow ice sheets to grow larger than during the

last glacial cycle. To investigate the impacts of such

a «super-glacial» we perform a time-slice which

includes ice sheets with 125% height of the LGM

size. Fig. 2 shows the comparison of the Northern

Hemisphere topography for the present state and

the setup used in the MIS4 125 simulation.

The dynamical response of the North Atlantic and

European climate to the 125%-LGM size ice sheet

is similar to the one observed with the 100% LGM

(simulations LGM and MIS4 LGM ). However, the comparison

of the «super-glacial» ice sheet (MIS4 125 )

with the last maximum (MIS4 LGM , Fig. 3) shows

that there is an additional strengthening of the

southward shift of the winter jet. These changes of

the jet position and strength lead to an additional

transport of moisture to the Iberian Peninsula and

also parts of Central Europe in winter (see Fig. 3c).

A similar response is observed in summer where

there is a strengthening of the jet and connected

with that an increase in mean precipitation at the

latitudes of the British Isles. Nevertheless, compared

with the pre-industrial simulation all parts

of Europe except some in the North experience

a strong drying during summer due to the vastly

colder temperatures (see also in Appendix Fig. A2).

Figure 1:

Schematic illustration

of the mean changes in

the glacial simulations

compared to the recent

past obtained for

winter.

Figure 2:

Topography in the

CCSM4 model for the

present state (used in

PI) and the state with

large ice sheets of

the size of 125% LGM

(used in MIS4 125 ).

Figure 3:

Winter (DJF, left column)

and summer

(JJA, right column)

differences between

MIS4_125 and

MIS4_LGM: surface

air temperature (a,b),

precipitation (c,d) and

zonal wind speed at

the 200hPa level (e,f).

Only values that are

statistically significant

at the 5% level (twosided

Student's t-test)

are colored.

ENSI Erfahrungs- und Forschungsbericht 2012 271

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