Abstract
In this chapter it is shown that the relationship between regional temperatures and large-scale circulation can change through time. The analysis is based on three 1000 year long quasiequilibrium simulations with the coupled atmosphere-ocean general circulation model ECHOG
for the Eemian interglacial, the last glacial inception and the preindustrial period, which differ with respect to the Earth’s orbit, and as a consequence with respect to the incoming solar radiation. The temperature signals of the Arctic Oscillation (AO) are compared and in
some regions noticeable differences are found. For instance during winter there is a clear signal in western Europe in the preindustrial but not in the Eemian simulation, whereas in
Siberia a strong signal is only found in the Eemian simulation. The results indicate in which regions an AO signal can be expected to be seen in temperature-sensitive proxy data with annual to multi-decadal temporal resolution. An analysis of the mean and the variability of the
atmospheric circulation suggest that the differences in the AO-temperature signal are mainly due to stronger mean westerly winds over Europe and western Siberia in the Eemian compared to the preindustrial period.
Based on the same simulations it is also shown that the spatial representativity of annual to decadal regional temperature variability differs between the three periods. For
regions with a strong AO temperature signal, the temperature representativity pattern strongly
resembles the AO temperature signal, and variations in the two patterns are closely related.
