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Browsing by Subject "ECHAM6"

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  • Koskentausta, Juho (2023)
    Global warming is rapidly reducing the Arctic sea ice cover. Along with its major impacts in the Arctic, the sea ice loss is known to affect the climate in remote continental areas. In this thesis, the remote effects are studied by analysing data from experiments carried out using the ECHAM6 atmospheric general circulation model forced with simple sea ice concentration and sea surface temperature configurations. The European and Asian midlatitude winter responses of surface air temperature are investigated, together with anomalies of variables potentially affecting them: sea level pressure, thermal advection, adiabatic and diabatic heating and surface energy fluxes. Arctic sea ice loss was found to have contributed weakly to the European warming from the 1980s to the 2010s. With sea ice and sea surface temperature conditions projected for 2071–2100, the warming response was about 1 °C relative to the 1979–2008 climatology, despite a negative North Atlantic Oscillation phase response. In Asia, the model simulates slight cooling of about 0.5 °C east of the Urals in the past and in the eastern parts of the continent in the future. However, the cooling responses are overwhelmed by the warming effect of global forcings. The effects of internal variability are large, and the role of the thermodynamic processes and surface energy fluxes in the link between the Arctic and Eurasia is not very clear. However, the temperature responses are mostly consistent with previous research, even though the model does not capture the observed past changes well.