Climate anomalies induced by the arctic and antarctic oscillations: Glacial maximum and present-day perspectives

Based on multicentury coupled climate simulations of both modern and glacial maximum conditions, this study focuses on the impact of the Arctic Oscillation (AO) and the Antarctic Oscillation (AAO) on the earth's surface climate. Intercomparison of the results obtained in numerical experiments for both climate epochs demonstrates that highly significant changes of surface climate are predicted to have occurred depending upon the phase of the AO and AAO. These climate anomalies differ substantially between the modern and Last Glacial Maximum (LGM) states and exhibit a strong seasonal cycle under the latter conditions. Additional investigation has revealed that an intensification of the subtropical gyres in the North Atlantic and North Pacific that are induced during the positive phase of the AO plays a key role in the development of positive sea surface temperature (SST) anomalies in midlatitudes. In the Southern Hemisphere, similarly significant and systematic climate shifts are shown to occur due to variations of the Antarctic Oscillation that are highlighted by a warming over the Antarctic Peninsula and midlatitudes during the positive phase of the AAO. Finally, the authors find that the temporal variability of the AO and of the Pacific decadal oscillation (PDO) is significantly anticorrelated, with this coupling being independent of the season under present-day conditions. Under LGM conditions, however, due to the intensified vigor of the atmospheric circulation, the coupling is found to be stronger during boreal winter.