Post-glacial climatic change and variability - The Global Climate System: Patterns, Processes, and Teleconnections - page 202

Younger Dryas. However, the cause for this event is not readily identifiable.
In addition, the great deal of variability in climatic records that mark the
MWP and the LIA within the last millennium is very indicative of the
regionalization of Holocene climate in the NH. The many factors that force
Holocene climate, including orbital, solar, volcanic, and greenhouse gas
components, act on varying time scales further enhancing the regionalization
of the post-glacial climate.
6.4 Southern Hemisphere climate reconstructions
The data to reconstruct past climates of the Holocene in the SH are much more
limited than the NH (Mann and Jones 2003 ; Jones and Mann 2004 ). Since the
SH is mostly ocean, proxies on land can only be drawn from Australia, Southern
Africa, South America, New Zealand, and Antarctica. Shallow ocean-based
proxies include coral and bottom sedimentation cores. Data before 1861 are
especially sparse (IPCC 2001 ). Jones et al.( 1998 ) list only seven major locations
where detailed good-quality longer-term records currently exist. These include
tree-ring records from Tasmania (Australia), and Lenca and Alerce (Argentina);
coral records from the Great Barrier Reef (Australia), Galapagos Islands (Chile),
and New Caledonia; and ice cores fromAntarctica. To this list can be added tree-
ring records from New Zealand, and ice-core information from Quelccanya,
Peru (Mann and Jones 2003 ), and speleothem information from Southern Africa
(Tyson et al. 2000 ).
As a result, conclusions about climate change and variability in the SH cannot
be as well defined or as representative as those for the NH. However, the data
are useful to provide some balance in the discussion for the globe, and individual
site results are comparable to their NH counterparts.
6.4.1 The 8200-year BP event in the Southern Hemisphere
The 8200-year BP event defined for the NH by Zielinski (Section 6.3.3 ,
Figure 6.5 ) also appears in the SH proxy records but not as strongly. Speleothem
results for New Zealand (Williams et al. 1999 ) suggest that the period 11 000
to 8500 BP was a warm, wet period, but subsequently temperatures declined.
There were small advances in New Zealand mountain glaciers between 8200 and
7800 BP (IPCC 2001 ). In Southern Africa, however, evidence for abrupt cooling
during this period is lacking (Lindesay 1998 ).
Stager and Mayewski ( 1997 ) provide data from the Taylor Dome ice core
in Antarctica which suggested a ''climatic reorganization'' that lasted about
200 years. Increased sodium (Na þ ) concentrations in the ice layers dated to this
period indicate an abrupt change to a more meridional circulation pattern, with