Spatiotemporal Variability of the Southern Annular Mode and its Influence on Antarctic Surface Temperatures

Beck, Christoph

Philipp, Andreas

Höppner, Kathrin

Jacobeit, Jucundus
DOI: https://doi.org/10.1029/2020JD033818
Persistent URL: http://resolver.sub.uni-goettingen.de/purl?gldocs-11858/8448
Philipp, Andreas; 2 Institute of Geography Augsburg University Augsburg Germany
Höppner, Kathrin; 3 Institute Development‐Space Research and Technology (VO‐IR) German Aerospace Center (DLR) Köln Germany
Jacobeit, Jucundus; 2 Institute of Geography Augsburg University Augsburg Germany
Abstract
The Southern Annular Mode (SAM) is the predominant atmospheric variability mode in the Southern Hemisphere. In this paper, we present the spatial variability results of the SAM pattern for the period 1979–2018. The SAM‐intrinsic pattern variability analysis is based on the principal component analysis (PCA), which is carried out for the ERA‐Interim 500 hPa geopotential height (GPH) data set. A spatiotemporally resolved data set of SAM pattern maps (PCA loadings) is derived by projecting monthly shifted sub‐sequences of SAM index values (PCA scores) on the corresponding GPH anomalies. The dominant SAM structure within single pattern fields is mapped automatically and can be interpreted as the Southern Hemisphere polar front. This data set allows an analysis of the geographical positions of the characteristic circumpolar SAM structure over four decades and shows considerable variability over space and time. Five different states of SAM patterns, which are associated with characteristic circulation anomalies during different phases of the study period, are identified. Station‐based Antarctic temperature anomalies can be synoptically explained by these circulation anomalies. The overall latitudinal trend of the SAM pattern indicates an intensification of the meridional structure, especially over the East Antarctic Southern Ocean. Furthermore, we show that the SAM pattern variability is significantly correlated with the Pacific Decadal Oscillation and the Atlantic Multidecadal Oscillation. Composites of 500 hPa GPH anomalies during the positive and negative phases of the respective indices indicate teleconnections with Pacific Decadal Oscillation and Atlantic Multidecadal Oscillation, and this can explain latitudinal trends of the SAM pattern.
Key Points:
We present a new approach to examine the spatiotemporal Southern Annular Mode pattern variability. Station‐based Antarctic temperature anomalies are related to different structures of the Southern Annular Mode. The trend pattern shows an increasing meridional structure and correlations with Pacific and Atlantic multidecadal oscillations.
Subjects
Southern Annular ModeSAM pattern variability
Antarctic circulation variability
Antarctic station temperature
PDO
AMO