Interpretation of Recent Southern Hemisphere Climate Change
David W. J. Thompson,1*
Susan Solomon2
Climate variability in the high-latitude Southern
Hemisphere (SH) is dominated by the SH annular mode, a large-scale
pattern of variability characterized by fluctuations in the strength of the circumpolar vortex. We present evidence that recent trends in the
SH tropospheric circulation can be interpreted as a bias toward the
high-index polarity of this pattern, with stronger westerly flow
encircling the polar cap. It is argued that the largest and most
significant tropospheric trends can be traced to recent trends in the
lower stratospheric polar vortex, which are due largely to
photochemical ozone losses. During the summer-fall season, the trend
toward stronger circumpolar flow has contributed substantially to the
observed warming over the Antarctic Peninsula and Patagonia and to the
cooling over eastern Antarctica and the Antarctic plateau.
1 Department of Atmospheric Science, Foothills
Campus, Colorado State University, Fort Collins, CO 80523, USA.
2 Aeronomy Laboratory, National Oceanic and
Atmospheric Administration, 325 South Broadway, Boulder, CO 80305, USA.
*
To whom correspondence should be addressed. E-mail:
davet{at}atmos.colostate.edu
