HR: 1330h
AN: PP52A-0963    [PDF]
TI: Global and Regional Modes of the Northern Hemisphere Atmospheric Circulation
AU: Rimbu, N
EM: nrim@palmod.uni-bremen.de
AF: Bremen University, Geoscience Department, Klagenfurtherstrasse, Bremen, D-28359 Germany
AU: Lohmann, G
EM: gerrit@palmod.uni-bremen.de
AF: Bremen University, Geoscience Department, Klagenfurtherstrasse, Bremen, D-28359 Germany
AU: Lorenz, S
EM: stephan.lorenz@dkrz.de
AF: Max-Planck Institute for Meteorology, Bundesstrasse 55, Hamburg, D-20146 Germany
AU: Felis, T
EM: tfelis@allgeo.uni-bremen.de
AF: Bremen University, Geoscience Department, Klagenfurtherstrasse, Bremen, D-28359 Germany
AU: * Grosfeld, K
EM: grosfeld@palmod.uni-bremen.de
AF: Bremen University, Geoscience Department, Klagenfurtherstrasse, Bremen, D-28359 Germany
AB: We investigate the relation between the North Atlantic Oscillation (NAO) and the Arctic Oscillation (AO) from the perspective of non-stationarity of Atlantic-Pacific atmospheric teleconnections. We detect decadal variations in the correlation of NAO and El Ni\~no-Southern Oscillation (ENSO) indices in observational data, proxy data and coupled ocean-atmosphere model simulations. During periods when the NAO and Ni\~no3 indices are significantly negative correlated the dominant mode of Northern Hemisphere atmospheric circulation has an annular structure similar to AO (global mode). For these periods NAO can be viewed as a regional manifestation of AO. During periods when NAO and Ni\~no3 indices are not significantly correlated the dominant mode of the Northern Hemisphere atmospheric circulation is concentrated in the Atlantic-European region and has a spatial structure similar to NAO (regional mode). During the last century, the global (regional) mode dominates the Northern Hemisphere circulation during the 1930s to 1960s (after the 1970s). The combined analysis of a snow accumulation time series from an ice core from Mount Logan (northwestern Canada) and a coral oxygen isotope time series from Ras Umm Sidd (northern Red Sea) reveals that the global mode dominates the Northern Hemisphere atmospheric circulation also during the 1750s to 1850s. The correlation between NAO and ENSO indices in a millennial-scale climate simulation of the coupled ocean-atmosphere model ECHO-G indicates decadal variations as detected in observed and proxy data. The model shows more frequent occurencies of global-mode regimes relative to regional-mode regimes, showing that a large part of millennial scale variability is related to AO.
DE: 0315 Biosphere/atmosphere interactions
DE: 3210 Modeling
DE: 3309 Climatology (1620)
DE: 3344 Paleoclimatology
DE: 3346 Planetary meteorology (5445, 5739)
SC: Paleoceanography and Paleoclimatology [PP]
MN: 2003 Fall Meeting