Late Quaternary environmental change in southern Africa
Date
2001Author
Partridge, T. C.
Odada, E. O.
Tyson, P. D.
Type
ArticleLanguage
enMetadata
Show full item recordAbstract
Over the last 400 000 years, the pattern of climatic change in the
southern African sector of the southern hemisphere is shown to
have followed in broad outline that defined by the Vostock ice-core
sequence. Regional-local differences are apparent in the inshore
ocean sediment core record taken from the continental shelf off
Namibia and probably relate to little-understood local processes.
Clear evidence of precessional Milankovitch forcing of climate is
evident for the subcontinent over the last 200 000 years. The Last
Glacial Maximum was coof and dry over most of non-equatorial
southern Africa, when the semi-permanent subtropical anticyclone
dominating the atmospheric circulation was displaced equatorward.
At the time, Lake Victoria was dry. Post-glacial warming culminated
in the Holocene altithermal, which reached its maximum
earlier than 6000 BP. Lake Victoria began to fill rapidly and overflowed
at around 7500 BP. Rapid speciation of local fishes occurred
in the lake at an unprecedented rate. Over the last 6000 years,
robust, spatially representative high-resolution speleothem
records from the summer rainfall region of the southern part of the
subcontinent reveal that a high degree of variability prevailed on
centennial to decadal scales. Abrupt changes, often over decades,
are a feature of the record. Whereas maximum heating in the
altithermal occurred before 6000 BP, the greatest extent of grass
cover characterized the landscape at around 2400-2000 BP. In the
last six millennia, the most pronounced and sustained event was
the five centuries of cooling during the Little Ice Age from AD 1300 to 1800.
Citation
South African Journal of Science 97, March/April 2001Publisher
bDepartment of Geology, University of Nairobi, Nairobi, Climatology Researcl1 Group. University of the Witwatersrand.