European winter temperature variability in a long coupled model simulation: the contribution of ocean dynamics |
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Authors: | Sebastian Wagner Stefanie Legutke Eduardo Zorita |
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Affiliation: | (1) Institute for Coastal Research, GKSS Research Center, Max-Planck-Str.1, 21502 Geesthacht, Germany;(2) Model & Data Group, Max-Planck-Institute of Meteorology, Hamburg, Germany;(3) Institute for Coastal Research, GKSS Research Center, Geesthacht, Germany |
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Abstract: | The interannual variability of the European winter air temperature is partially caused by anomalous atmospheric circulation
and the associated advection of air masses, mainly linked to the North Atlantic Oscillation (NAO). However, a considerable
part of the temperature variability is not linearly described by atmospheric circulation anomalies. Here, a long control simulation
with a coupled atmosphere-ocean climate model is analyzed, with the goal of decomposing the European temperature (ET) anomalies
in a part linked to the anomalous atmospheric circulation and a residual. The amount of interannual variability of each contribution
is roughly 50%, although at subdecadal (overdecadal) time scales the variability of the residuals is dominant. These residuals
are found to be linked to temperature anomalies of the same sign in the whole North Atlantic and Greenland, in contrast to
the well-known temperature zonal seesaw associated with the NAO. The association between the residuals and other processes
in the North Atlantic has been also analyzed. The thermohaline circulation, closely connected in the model to the intensity
of the Gulf Stream, lags the evolution of the temperature residuals by several years and thus is not able to control their
evolution. The variability of the oceanic convection in the Northern North Atlantic, on the other hand, correlates with the
temperature residual at lags close to zero. It is hypothesized that oceanic convection produces a sea-surface temperature
fingerprint that leads to the ET residuals. The implications of these results for multi-year predictability and for empirical
climate reconstructions are discussed. |
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