Tuesday, 13 May 2003: 1:30 PM
Observed mean sea level pressure records are used to construct a set
of indices related to Southern Hemispheric Climate variability
from 1884 to 2001. We focus on
the Southern Annular Mode (SAM), a pressure sea-saw between Antarctica and
the subtropical high pressure regions. Station availability restricts
the regional analysis was restricted to three high pressure regions centered
around South America, South Africa and Australia/New Zealand.
All three regions have several stations with long surface pressure time series.
Pressure data from the Antarctic continent are only available since 1954 which restricts the reconstruction of a SAM index to post 1954. However, a method was
developed that allowed the reconstruction of Antarctic pressure anomalies back to 1884. Regional correlation of the monthly and annual SAM index
with surface winds, sea ice cover and surface temperatures are presented.
Finally the recent "trend" in the SAM index is proposed as a possible cause
for the observed warming in upper ocean temperatures and increase in sea ice cover
in the southern hemispheric polar region.
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