Die Arktische Oszillation im Kieler Klimamodell

• Main Author: Schaffer, Janin
• Format: Thesis
• Language: German
• Published: 2010
• Subjects: Course of study: BSc Physics of the Earth System; Arctic; Pacific; Randall; Arktis*; Climate change; North Atlantic
• Online Access: https://oceanrep.geomar.de/id/eprint/11836/; https://oceanrep.geomar.de/id/eprint/11836/1/Schaffer.pdf

The Arctic Oscillation (AO) is the dominant mode of variability of the mean sea level pressure (MSLP) in the Northern hemisphere. It is a result of an EOF-analysis for SLP3 anomalies during winter. Because of a decisive influence of the AO on atmospheric processes in the troposphere and stratosphere (Randall et al., 2007), it is of interest how the AO behaves during changing climatological conditions. Therefore three runs of the Kiel Climate Model (KCM) will be analyzed considering the AO: a control run with pre-industrial CO2-level, an A1B scenario and a scenario in which the CO2-level will change by one percent per year until a doubling of the pre-industrial CO2-level is reached ongoing with a stabilization period. Comparing the AO of the control run with the AO of the CO2-forced run the result reaches an equal anomaly in the Arctic centre. By contrast the variability in the western North Atlantic Ocean is sinking while it is clearly rising in the North Pacific Ocean. Additionally the second EOF indicates an increasing variability in the Pacific Ocean, while it is also presenting a higher degree regarding the overall variability. As a result of the temporal evolution of the AO, calculated for the control run, in the forced scenario there is a distinctive positive trend in the AO-Index. This implies a lower SLP than the average in the Arctic. In order to classify the results of the KCM, the AO of the A1B scenario in the period of 1950 to 1999 of the KCM is compared to results simulated by the Intergovernmental Panel on Climate Change Fourth Assessment Report (IPCC AR4) ensembles of 14 coupled atmosphere-ocean-models, the resulting Multi-Model and observed data with regard to Miller et al. (2006). The observed data indicate as well as the A1B scenario of the KCM and the Multi-Model a positive trend in the AO-Index but the magnitude is varying. The results of the spatial distribution of the variability are showing a strong dispersion in between the models. The variability in the North Pacific Ocean is ...