Tropical Connections to Climatic Change in the Extratropical Southern Hemisphere: The Role of Atlantic SST Trends

The austral spring relationships between sea surface temperature (SST) trends and the Southern Hemi-sphere (SH) extratropical atmospheric circulation are investigated using an atmospheric general circulation model (AGCM). A suite of simulations are analyzed wherein the AGCM is forced by underlying S...

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Bibliographic Details
Main Authors: Graham R. Simpkins, Shayne Mcgregor, S. Taschetto, Laura M. Ciasto, Matthew H. England
Other Authors: The Pennsylvania State University CiteSeerX Archives
Format: Text
Language:English
Published: 2013
Subjects:
Antarctic
Antarctic Peninsula
Austral
Indian
Pacific
The Antarctic
Antarc*
Online Access:http://citeseerx.ist.psu.edu/viewdoc/summary?doi=10.1.1.684.2367
http://web.science.unsw.edu.au/%7Ematthew/Simpkins_et_al_2014_JCLIM.pdf
Description
Summary:The austral spring relationships between sea surface temperature (SST) trends and the Southern Hemi-sphere (SH) extratropical atmospheric circulation are investigated using an atmospheric general circulation model (AGCM). A suite of simulations are analyzed wherein the AGCM is forced by underlying SST con-ditions in which recent trends are constrained to individual ocean basins (Pacific, Indian, and Atlantic), allowing the impact of each region to be assessed in isolation. When forced with observed global SST, the model broadly replicates the spatial pattern of extratropical SH geopotential height trends seen in reanalyses. However, when forcing by each ocean basin separately, similar structures arise only whenAtlantic SST trends are included. It is further shown that teleconnections from the Atlantic are associated with perturbations to the zonal Walker circulation and the corresponding intensification of the local Hadley cell, the impact of which results in the development of atmospheric Rossby waves. Thus, increased Rossby waves, forced by positive Atlantic SST trends, may have played a role in driving geopotential height trends in the SH extra-tropics. Furthermore, these atmospheric circulation changes promote warming throughout the Antarctic Peninsula andmuch ofWestAntarctica, with a pattern that closelymatches recent observational records. This suggests that Atlantic SST trends, via a teleconnection to the SH extratropics, may have contributed to springtime climatic change in the SH extratropics over the past three decades. 1.

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